diff options
| author | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2015-08-05 17:04:01 -0300 |
|---|---|---|
| committer | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2015-08-05 17:04:01 -0300 |
| commit | 57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch) | |
| tree | 5e910f0e82173f4ef4f51111366a3f1299037a7b /Documentation/i2c | |
Initial import
Diffstat (limited to 'Documentation/i2c')
36 files changed, 3526 insertions, 0 deletions
diff --git a/Documentation/i2c/busses/i2c-ali1535 b/Documentation/i2c/busses/i2c-ali1535 new file mode 100644 index 000000000..5d46342e4 --- /dev/null +++ b/Documentation/i2c/busses/i2c-ali1535 @@ -0,0 +1,42 @@ +Kernel driver i2c-ali1535 + +Supported adapters: + * Acer Labs, Inc. ALI 1535 (south bridge) + Datasheet: Now under NDA + http://www.ali.com.tw/ + +Authors: + Frodo Looijaard <frodol@dds.nl>, + Philip Edelbrock <phil@netroedge.com>, + Mark D. Studebaker <mdsxyz123@yahoo.com>, + Dan Eaton <dan.eaton@rocketlogix.com>, + Stephen Rousset<stephen.rousset@rocketlogix.com> + +Description +----------- + +This is the driver for the SMB Host controller on Acer Labs Inc. (ALI) +M1535 South Bridge. + +The M1535 is a South bridge for portable systems. It is very similar to the +M15x3 South bridges also produced by Acer Labs Inc. Some of the registers +within the part have moved and some have been redefined slightly. +Additionally, the sequencing of the SMBus transactions has been modified to +be more consistent with the sequencing recommended by the manufacturer and +observed through testing. These changes are reflected in this driver and +can be identified by comparing this driver to the i2c-ali15x3 driver. For +an overview of these chips see http://www.acerlabs.com + +The SMB controller is part of the M7101 device, which is an ACPI-compliant +Power Management Unit (PMU). + +The whole M7101 device has to be enabled for the SMB to work. You can't +just enable the SMB alone. The SMB and the ACPI have separate I/O spaces. +We make sure that the SMB is enabled. We leave the ACPI alone. + + +Features +-------- + +This driver controls the SMB Host only. This driver does not use +interrupts. diff --git a/Documentation/i2c/busses/i2c-ali1563 b/Documentation/i2c/busses/i2c-ali1563 new file mode 100644 index 000000000..41b1a077e --- /dev/null +++ b/Documentation/i2c/busses/i2c-ali1563 @@ -0,0 +1,27 @@ +Kernel driver i2c-ali1563 + +Supported adapters: + * Acer Labs, Inc. ALI 1563 (south bridge) + Datasheet: Now under NDA + http://www.ali.com.tw/ + +Author: Patrick Mochel <mochel@digitalimplant.org> + +Description +----------- + +This is the driver for the SMB Host controller on Acer Labs Inc. (ALI) +M1563 South Bridge. + +For an overview of these chips see http://www.acerlabs.com + +The M1563 southbridge is deceptively similar to the M1533, with a few +notable exceptions. One of those happens to be the fact they upgraded the +i2c core to be SMBus 2.0 compliant, and happens to be almost identical to +the i2c controller found in the Intel 801 south bridges. + +Features +-------- + +This driver controls the SMB Host only. This driver does not use +interrupts. diff --git a/Documentation/i2c/busses/i2c-ali15x3 b/Documentation/i2c/busses/i2c-ali15x3 new file mode 100644 index 000000000..42888d8ac --- /dev/null +++ b/Documentation/i2c/busses/i2c-ali15x3 @@ -0,0 +1,112 @@ +Kernel driver i2c-ali15x3 + +Supported adapters: + * Acer Labs, Inc. ALI 1533 and 1543C (south bridge) + Datasheet: Now under NDA + http://www.ali.com.tw/ + +Authors: + Frodo Looijaard <frodol@dds.nl>, + Philip Edelbrock <phil@netroedge.com>, + Mark D. Studebaker <mdsxyz123@yahoo.com> + +Module Parameters +----------------- + +* force_addr: int + Initialize the base address of the i2c controller + + +Notes +----- + +The force_addr parameter is useful for boards that don't set the address in +the BIOS. Does not do a PCI force; the device must still be present in +lspci. Don't use this unless the driver complains that the base address is +not set. + +Example: 'modprobe i2c-ali15x3 force_addr=0xe800' + +SMBus periodically hangs on ASUS P5A motherboards and can only be cleared +by a power cycle. Cause unknown (see Issues below). + + +Description +----------- + +This is the driver for the SMB Host controller on Acer Labs Inc. (ALI) +M1541 and M1543C South Bridges. + +The M1543C is a South bridge for desktop systems. +The M1541 is a South bridge for portable systems. +They are part of the following ALI chipsets: + + * "Aladdin Pro 2" includes the M1621 Slot 1 North bridge with AGP and + 100MHz CPU Front Side bus + * "Aladdin V" includes the M1541 Socket 7 North bridge with AGP and 100MHz + CPU Front Side bus + Some Aladdin V motherboards: + Asus P5A + Atrend ATC-5220 + BCM/GVC VP1541 + Biostar M5ALA + Gigabyte GA-5AX (** Generally doesn't work because the BIOS doesn't + enable the 7101 device! **) + Iwill XA100 Plus + Micronics C200 + Microstar (MSI) MS-5169 + + * "Aladdin IV" includes the M1541 Socket 7 North bridge + with host bus up to 83.3 MHz. + +For an overview of these chips see http://www.acerlabs.com. At this time the +full data sheets on the web site are password protected, however if you +contact the ALI office in San Jose they may give you the password. + +The M1533/M1543C devices appear as FOUR separate devices on the PCI bus. An +output of lspci will show something similar to the following: + + 00:02.0 USB Controller: Acer Laboratories Inc. M5237 (rev 03) + 00:03.0 Bridge: Acer Laboratories Inc. M7101 <= THIS IS THE ONE WE NEED + 00:07.0 ISA bridge: Acer Laboratories Inc. M1533 (rev c3) + 00:0f.0 IDE interface: Acer Laboratories Inc. M5229 (rev c1) + +** IMPORTANT ** +** If you have a M1533 or M1543C on the board and you get +** "ali15x3: Error: Can't detect ali15x3!" +** then run lspci. +** If you see the 1533 and 5229 devices but NOT the 7101 device, +** then you must enable ACPI, the PMU, SMB, or something similar +** in the BIOS. +** The driver won't work if it can't find the M7101 device. + +The SMB controller is part of the M7101 device, which is an ACPI-compliant +Power Management Unit (PMU). + +The whole M7101 device has to be enabled for the SMB to work. You can't +just enable the SMB alone. The SMB and the ACPI have separate I/O spaces. +We make sure that the SMB is enabled. We leave the ACPI alone. + +Features +-------- + +This driver controls the SMB Host only. The SMB Slave +controller on the M15X3 is not enabled. This driver does not use +interrupts. + + +Issues +------ + +This driver requests the I/O space for only the SMB +registers. It doesn't use the ACPI region. + +On the ASUS P5A motherboard, there are several reports that +the SMBus will hang and this can only be resolved by +powering off the computer. It appears to be worse when the board +gets hot, for example under heavy CPU load, or in the summer. +There may be electrical problems on this board. +On the P5A, the W83781D sensor chip is on both the ISA and +SMBus. Therefore the SMBus hangs can generally be avoided +by accessing the W83781D on the ISA bus only. + diff --git a/Documentation/i2c/busses/i2c-amd756 b/Documentation/i2c/busses/i2c-amd756 new file mode 100644 index 000000000..67f30874d --- /dev/null +++ b/Documentation/i2c/busses/i2c-amd756 @@ -0,0 +1,25 @@ +Kernel driver i2c-amd756 + +Supported adapters: + * AMD 756 + * AMD 766 + * AMD 768 + * AMD 8111 + Datasheets: Publicly available on AMD website + + * nVidia nForce + Datasheet: Unavailable + +Authors: + Frodo Looijaard <frodol@dds.nl>, + Philip Edelbrock <phil@netroedge.com> + +Description +----------- + +This driver supports the AMD 756, 766, 768 and 8111 Peripheral Bus +Controllers, and the nVidia nForce. + +Note that for the 8111, there are two SMBus adapters. The SMBus 1.0 adapter +is supported by this driver, and the SMBus 2.0 adapter is supported by the +i2c-amd8111 driver. diff --git a/Documentation/i2c/busses/i2c-amd8111 b/Documentation/i2c/busses/i2c-amd8111 new file mode 100644 index 000000000..460dd6635 --- /dev/null +++ b/Documentation/i2c/busses/i2c-amd8111 @@ -0,0 +1,41 @@ +Kernel driver i2c-adm8111 + +Supported adapters: + * AMD-8111 SMBus 2.0 PCI interface + +Datasheets: + AMD datasheet not yet available, but almost everything can be found + in the publicly available ACPI 2.0 specification, which the adapter + follows. + +Author: Vojtech Pavlik <vojtech@suse.cz> + +Description +----------- + +If you see something like this: + +00:07.2 SMBus: Advanced Micro Devices [AMD] AMD-8111 SMBus 2.0 (rev 02) + Subsystem: Advanced Micro Devices [AMD] AMD-8111 SMBus 2.0 + Flags: medium devsel, IRQ 19 + I/O ports at d400 [size=32] + +in your 'lspci -v', then this driver is for your chipset. + +Process Call Support +-------------------- + +Supported. + +SMBus 2.0 Support +----------------- + +Supported. Both PEC and block process call support is implemented. Slave +mode or host notification are not yet implemented. + +Notes +----- + +Note that for the 8111, there are two SMBus adapters. The SMBus 2.0 adapter +is supported by this driver, and the SMBus 1.0 adapter is supported by the +i2c-amd756 driver. diff --git a/Documentation/i2c/busses/i2c-diolan-u2c b/Documentation/i2c/busses/i2c-diolan-u2c new file mode 100644 index 000000000..0d6018c31 --- /dev/null +++ b/Documentation/i2c/busses/i2c-diolan-u2c @@ -0,0 +1,26 @@ +Kernel driver i2c-diolan-u2c + +Supported adapters: + * Diolan U2C-12 I2C-USB adapter + Documentation: + http://www.diolan.com/i2c/u2c12.html + +Author: Guenter Roeck <linux@roeck-us.net> + +Description +----------- + +This is the driver for the Diolan U2C-12 USB-I2C adapter. + +The Diolan U2C-12 I2C-USB Adapter provides a low cost solution to connect +a computer to I2C slave devices using a USB interface. It also supports +connectivity to SPI devices. + +This driver only supports the I2C interface of U2C-12. The driver does not use +interrupts. + + +Module parameters +----------------- + +* frequency: I2C bus frequency diff --git a/Documentation/i2c/busses/i2c-i801 b/Documentation/i2c/busses/i2c-i801 new file mode 100644 index 000000000..82f48f774 --- /dev/null +++ b/Documentation/i2c/busses/i2c-i801 @@ -0,0 +1,164 @@ +Kernel driver i2c-i801 + +Supported adapters: + * Intel 82801AA and 82801AB (ICH and ICH0 - part of the + '810' and '810E' chipsets) + * Intel 82801BA (ICH2 - part of the '815E' chipset) + * Intel 82801CA/CAM (ICH3) + * Intel 82801DB (ICH4) (HW PEC supported) + * Intel 82801EB/ER (ICH5) (HW PEC supported) + * Intel 6300ESB + * Intel 82801FB/FR/FW/FRW (ICH6) + * Intel 82801G (ICH7) + * Intel 631xESB/632xESB (ESB2) + * Intel 82801H (ICH8) + * Intel 82801I (ICH9) + * Intel EP80579 (Tolapai) + * Intel 82801JI (ICH10) + * Intel 5/3400 Series (PCH) + * Intel 6 Series (PCH) + * Intel Patsburg (PCH) + * Intel DH89xxCC (PCH) + * Intel Panther Point (PCH) + * Intel Lynx Point (PCH) + * Intel Lynx Point-LP (PCH) + * Intel Avoton (SOC) + * Intel Wellsburg (PCH) + * Intel Coleto Creek (PCH) + * Intel Wildcat Point (PCH) + * Intel Wildcat Point-LP (PCH) + * Intel BayTrail (SOC) + * Intel Sunrise Point-H (PCH) + * Intel Sunrise Point-LP (PCH) + Datasheets: Publicly available at the Intel website + +On Intel Patsburg and later chipsets, both the normal host SMBus controller +and the additional 'Integrated Device Function' controllers are supported. + +Authors: + Mark Studebaker <mdsxyz123@yahoo.com> + Jean Delvare <jdelvare@suse.de> + + +Module Parameters +----------------- + +* disable_features (bit vector) +Disable selected features normally supported by the device. This makes it +possible to work around possible driver or hardware bugs if the feature in +question doesn't work as intended for whatever reason. Bit values: + 0x01 disable SMBus PEC + 0x02 disable the block buffer + 0x08 disable the I2C block read functionality + 0x10 don't use interrupts + + +Description +----------- + +The ICH (properly known as the 82801AA), ICH0 (82801AB), ICH2 (82801BA), +ICH3 (82801CA/CAM) and later devices (PCH) are Intel chips that are a part of +Intel's '810' chipset for Celeron-based PCs, '810E' chipset for +Pentium-based PCs, '815E' chipset, and others. + +The ICH chips contain at least SEVEN separate PCI functions in TWO logical +PCI devices. An output of lspci will show something similar to the +following: + + 00:1e.0 PCI bridge: Intel Corporation: Unknown device 2418 (rev 01) + 00:1f.0 ISA bridge: Intel Corporation: Unknown device 2410 (rev 01) + 00:1f.1 IDE interface: Intel Corporation: Unknown device 2411 (rev 01) + 00:1f.2 USB Controller: Intel Corporation: Unknown device 2412 (rev 01) + 00:1f.3 Unknown class [0c05]: Intel Corporation: Unknown device 2413 (rev 01) + +The SMBus controller is function 3 in device 1f. Class 0c05 is SMBus Serial +Controller. + +The ICH chips are quite similar to Intel's PIIX4 chip, at least in the +SMBus controller. + + +Process Call Support +-------------------- + +Not supported. + + +I2C Block Read Support +---------------------- + +I2C block read is supported on the 82801EB (ICH5) and later chips. + + +SMBus 2.0 Support +----------------- + +The 82801DB (ICH4) and later chips support several SMBus 2.0 features. + + +Interrupt Support +----------------- + +PCI interrupt support is supported on the 82801EB (ICH5) and later chips. + + +Hidden ICH SMBus +---------------- + +If your system has an Intel ICH south bridge, but you do NOT see the +SMBus device at 00:1f.3 in lspci, and you can't figure out any way in the +BIOS to enable it, it means it has been hidden by the BIOS code. Asus is +well known for first doing this on their P4B motherboard, and many other +boards after that. Some vendor machines are affected as well. + +The first thing to try is the "i2c_ec" ACPI driver. It could be that the +SMBus was hidden on purpose because it'll be driven by ACPI. If the +i2c_ec driver works for you, just forget about the i2c-i801 driver and +don't try to unhide the ICH SMBus. Even if i2c_ec doesn't work, you +better make sure that the SMBus isn't used by the ACPI code. Try loading +the "fan" and "thermal" drivers, and check in /proc/acpi/fan and +/proc/acpi/thermal_zone. If you find anything there, it's likely that +the ACPI is accessing the SMBus and it's safer not to unhide it. Only +once you are certain that ACPI isn't using the SMBus, you can attempt +to unhide it. + +In order to unhide the SMBus, we need to change the value of a PCI +register before the kernel enumerates the PCI devices. This is done in +drivers/pci/quirks.c, where all affected boards must be listed (see +function asus_hides_smbus_hostbridge.) If the SMBus device is missing, +and you think there's something interesting on the SMBus (e.g. a +hardware monitoring chip), you need to add your board to the list. + +The motherboard is identified using the subvendor and subdevice IDs of the +host bridge PCI device. Get yours with "lspci -n -v -s 00:00.0": + +00:00.0 Class 0600: 8086:2570 (rev 02) + Subsystem: 1043:80f2 + Flags: bus master, fast devsel, latency 0 + Memory at fc000000 (32-bit, prefetchable) [size=32M] + Capabilities: [e4] #09 [2106] + Capabilities: [a0] AGP version 3.0 + +Here the host bridge ID is 2570 (82865G/PE/P), the subvendor ID is 1043 +(Asus) and the subdevice ID is 80f2 (P4P800-X). You can find the symbolic +names for the bridge ID and the subvendor ID in include/linux/pci_ids.h, +and then add a case for your subdevice ID at the right place in +drivers/pci/quirks.c. Then please give it very good testing, to make sure +that the unhidden SMBus doesn't conflict with e.g. ACPI. + +If it works, proves useful (i.e. there are usable chips on the SMBus) +and seems safe, please submit a patch for inclusion into the kernel. + +Note: There's a useful script in lm_sensors 2.10.2 and later, named +unhide_ICH_SMBus (in prog/hotplug), which uses the fakephp driver to +temporarily unhide the SMBus without having to patch and recompile your +kernel. It's very convenient if you just want to check if there's +anything interesting on your hidden ICH SMBus. + + +********************** +The lm_sensors project gratefully acknowledges the support of Texas +Instruments in the initial development of this driver. + +The lm_sensors project gratefully acknowledges the support of Intel in the +development of SMBus 2.0 / ICH4 features of this driver. diff --git a/Documentation/i2c/busses/i2c-ismt b/Documentation/i2c/busses/i2c-ismt new file mode 100644 index 000000000..737355822 --- /dev/null +++ b/Documentation/i2c/busses/i2c-ismt @@ -0,0 +1,36 @@ +Kernel driver i2c-ismt + +Supported adapters: + * Intel S12xx series SOCs + +Authors: + Bill Brown <bill.e.brown@intel.com> + + +Module Parameters +----------------- + +* bus_speed (unsigned int) +Allows changing of the bus speed. Normally, the bus speed is set by the BIOS +and never needs to be changed. However, some SMBus analyzers are too slow for +monitoring the bus during debug, thus the need for this module parameter. +Specify the bus speed in kHz. +Available bus frequency settings: + 0 no change + 80 kHz + 100 kHz + 400 kHz + 1000 kHz + + +Description +----------- + +The S12xx series of SOCs have a pair of integrated SMBus 2.0 controllers +targeted primarily at the microserver and storage markets. + +The S12xx series contain a pair of PCI functions. An output of lspci will show +something similar to the following: + + 00:13.0 System peripheral: Intel Corporation Centerton SMBus 2.0 Controller 0 + 00:13.1 System peripheral: Intel Corporation Centerton SMBus 2.0 Controller 1 diff --git a/Documentation/i2c/busses/i2c-nforce2 b/Documentation/i2c/busses/i2c-nforce2 new file mode 100644 index 000000000..9698c396b --- /dev/null +++ b/Documentation/i2c/busses/i2c-nforce2 @@ -0,0 +1,50 @@ +Kernel driver i2c-nforce2 + +Supported adapters: + * nForce2 MCP 10de:0064 + * nForce2 Ultra 400 MCP 10de:0084 + * nForce3 Pro150 MCP 10de:00D4 + * nForce3 250Gb MCP 10de:00E4 + * nForce4 MCP 10de:0052 + * nForce4 MCP-04 10de:0034 + * nForce MCP51 10de:0264 + * nForce MCP55 10de:0368 + * nForce MCP61 10de:03EB + * nForce MCP65 10de:0446 + * nForce MCP67 10de:0542 + * nForce MCP73 10de:07D8 + * nForce MCP78S 10de:0752 + * nForce MCP79 10de:0AA2 + +Datasheet: not publicly available, but seems to be similar to the + AMD-8111 SMBus 2.0 adapter. + +Authors: + Hans-Frieder Vogt <hfvogt@gmx.net>, + Thomas Leibold <thomas@plx.com>, + Patrick Dreker <patrick@dreker.de> + +Description +----------- + +i2c-nforce2 is a driver for the SMBuses included in the nVidia nForce2 MCP. + +If your 'lspci -v' listing shows something like the following, + +00:01.1 SMBus: nVidia Corporation: Unknown device 0064 (rev a2) + Subsystem: Asustek Computer, Inc.: Unknown device 0c11 + Flags: 66Mhz, fast devsel, IRQ 5 + I/O ports at c000 [size=32] + Capabilities: <available only to root> + +then this driver should support the SMBuses of your motherboard. + + +Notes +----- + +The SMBus adapter in the nForce2 chipset seems to be very similar to the +SMBus 2.0 adapter in the AMD-8111 south bridge. However, I could only get +the driver to work with direct I/O access, which is different to the EC +interface of the AMD-8111. Tested on Asus A7N8X. The ACPI DSDT table of the +Asus A7N8X lists two SMBuses, both of which are supported by this driver. diff --git a/Documentation/i2c/busses/i2c-ocores b/Documentation/i2c/busses/i2c-ocores new file mode 100644 index 000000000..c269aaa2f --- /dev/null +++ b/Documentation/i2c/busses/i2c-ocores @@ -0,0 +1,68 @@ +Kernel driver i2c-ocores + +Supported adapters: + * OpenCores.org I2C controller by Richard Herveille (see datasheet link) + Datasheet: http://www.opencores.org/projects.cgi/web/i2c/overview + +Author: Peter Korsgaard <jacmet@sunsite.dk> + +Description +----------- + +i2c-ocores is an i2c bus driver for the OpenCores.org I2C controller +IP core by Richard Herveille. + +Usage +----- + +i2c-ocores uses the platform bus, so you need to provide a struct +platform_device with the base address and interrupt number. The +dev.platform_data of the device should also point to a struct +ocores_i2c_platform_data (see linux/i2c-ocores.h) describing the +distance between registers and the input clock speed. +There is also a possibility to attach a list of i2c_board_info which +the i2c-ocores driver will add to the bus upon creation. + +E.G. something like: + +static struct resource ocores_resources[] = { + [0] = { + .start = MYI2C_BASEADDR, + .end = MYI2C_BASEADDR + 8, + .flags = IORESOURCE_MEM, + }, + [1] = { + .start = MYI2C_IRQ, + .end = MYI2C_IRQ, + .flags = IORESOURCE_IRQ, + }, +}; + +/* optional board info */ +struct i2c_board_info ocores_i2c_board_info[] = { + { + I2C_BOARD_INFO("tsc2003", 0x48), + .platform_data = &tsc2003_platform_data, + .irq = TSC_IRQ + }, + { + I2C_BOARD_INFO("adv7180", 0x42 >> 1), + .irq = ADV_IRQ + } +}; + +static struct ocores_i2c_platform_data myi2c_data = { + .regstep = 2, /* two bytes between registers */ + .clock_khz = 50000, /* input clock of 50MHz */ + .devices = ocores_i2c_board_info, /* optional table of devices */ + .num_devices = ARRAY_SIZE(ocores_i2c_board_info), /* table size */ +}; + +static struct platform_device myi2c = { + .name = "ocores-i2c", + .dev = { + .platform_data = &myi2c_data, + }, + .num_resources = ARRAY_SIZE(ocores_resources), + .resource = ocores_resources, +}; diff --git a/Documentation/i2c/busses/i2c-parport b/Documentation/i2c/busses/i2c-parport new file mode 100644 index 000000000..0e2d17b46 --- /dev/null +++ b/Documentation/i2c/busses/i2c-parport @@ -0,0 +1,177 @@ +Kernel driver i2c-parport + +Author: Jean Delvare <jdelvare@suse.de> + +This is a unified driver for several i2c-over-parallel-port adapters, +such as the ones made by Philips, Velleman or ELV. This driver is +meant as a replacement for the older, individual drivers: + * i2c-philips-par + * i2c-elv + * i2c-velleman + * video/i2c-parport (NOT the same as this one, dedicated to home brew + teletext adapters) + +It currently supports the following devices: + * (type=0) Philips adapter + * (type=1) home brew teletext adapter + * (type=2) Velleman K8000 adapter + * (type=3) ELV adapter + * (type=4) Analog Devices ADM1032 evaluation board + * (type=5) Analog Devices evaluation boards: ADM1025, ADM1030, ADM1031 + * (type=6) Barco LPT->DVI (K5800236) adapter + * (type=7) One For All JP1 parallel port adapter + +These devices use different pinout configurations, so you have to tell +the driver what you have, using the type module parameter. There is no +way to autodetect the devices. Support for different pinout configurations +can be easily added when needed. + +Earlier kernels defaulted to type=0 (Philips). But now, if the type +parameter is missing, the driver will simply fail to initialize. + +SMBus alert support is available on adapters which have this line properly +connected to the parallel port's interrupt pin. + + +Building your own adapter +------------------------- + +If you want to build you own i2c-over-parallel-port adapter, here is +a sample electronics schema (credits go to Sylvain Munaut): + +Device PC +Side ___________________Vdd (+) Side + | | | + --- --- --- + | | | | | | + |R| |R| |R| + | | | | | | + --- --- --- + | | | + | | /| | +SCL ----------x--------o |-----------x------------------- pin 2 + | \| | | + | | | + | |\ | | +SDA ----------x----x---| o---x--------------------------- pin 13 + | |/ | + | | + | /| | + ---------o |----------------x-------------- pin 3 + \| | | + | | + --- --- + | | | | + |R| |R| + | | | | + --- --- + | | + ### ### + GND GND + +Remarks: + - This is the exact pinout and electronics used on the Analog Devices + evaluation boards. + /| + - All inverters -o |- must be 74HC05, they must be open collector output. + \| + - All resitors are 10k. + - Pins 18-25 of the parallel port connected to GND. + - Pins 4-9 (D2-D7) could be used as VDD is the driver drives them high. + The ADM1032 evaluation board uses D4-D7. Beware that the amount of + current you can draw from the parallel port is limited. Also note that + all connected lines MUST BE driven at the same state, else you'll short + circuit the output buffers! So plugging the I2C adapter after loading + the i2c-parport module might be a good safety since data line state + prior to init may be unknown. + - This is 5V! + - Obviously you cannot read SCL (so it's not really standard-compliant). + Pretty easy to add, just copy the SDA part and use another input pin. + That would give (ELV compatible pinout): + + +Device PC +Side ______________________________Vdd (+) Side + | | | | + --- --- --- --- + | | | | | | | | + |R| |R| |R| |R| + | | | | | | | | + --- --- --- --- + | | | | + | | |\ | | +SCL ----------x--------x--| o---x------------------------ pin 15 + | | |/ | + | | | + | | /| | + | ---o |-------------x-------------- pin 2 + | \| | | + | | | + | | | + | |\ | | +SDA ---------------x---x--| o--------x------------------- pin 10 + | |/ | + | | + | /| | + ---o |------------------x--------- pin 3 + \| | | + | | + --- --- + | | | | + |R| |R| + | | | | + --- --- + | | + ### ### + GND GND + + +If possible, you should use the same pinout configuration as existing +adapters do, so you won't even have to change the code. + + +Similar (but different) drivers +------------------------------- + +This driver is NOT the same as the i2c-pport driver found in the i2c +package. The i2c-pport driver makes use of modern parallel port features so +that you don't need additional electronics. It has other restrictions +however, and was not ported to Linux 2.6 (yet). + +This driver is also NOT the same as the i2c-pcf-epp driver found in the +lm_sensors package. The i2c-pcf-epp driver doesn't use the parallel port as +an I2C bus directly. Instead, it uses it to control an external I2C bus +master. That driver was not ported to Linux 2.6 (yet) either. + + +Legacy documentation for Velleman adapter +----------------------------------------- + +Useful links: +Velleman http://www.velleman.be/ +Velleman K8000 Howto http://howto.htlw16.ac.at/k8000-howto.html + +The project has lead to new libs for the Velleman K8000 and K8005: + LIBK8000 v1.99.1 and LIBK8005 v0.21 +With these libs, you can control the K8000 interface card and the K8005 +stepper motor card with the simple commands which are in the original +Velleman software, like SetIOchannel, ReadADchannel, SendStepCCWFull and +many more, using /dev/velleman. + http://home.wanadoo.nl/hihihi/libk8000.htm + http://home.wanadoo.nl/hihihi/libk8005.htm + http://struyve.mine.nu:8080/index.php?block=k8000 + http://sourceforge.net/projects/libk8005/ + + +One For All JP1 parallel port adapter +------------------------------------- + +The JP1 project revolves around a set of remote controls which expose +the I2C bus their internal configuration EEPROM lives on via a 6 pin +jumper in the battery compartment. More details can be found at: + +http://www.hifi-remote.com/jp1/ + +Details of the simple parallel port hardware can be found at: + +http://www.hifi-remote.com/jp1/hardware.shtml diff --git a/Documentation/i2c/busses/i2c-parport-light b/Documentation/i2c/busses/i2c-parport-light new file mode 100644 index 000000000..7071b8ba0 --- /dev/null +++ b/Documentation/i2c/busses/i2c-parport-light @@ -0,0 +1,22 @@ +Kernel driver i2c-parport-light + +Author: Jean Delvare <jdelvare@suse.de> + +This driver is a light version of i2c-parport. It doesn't depend +on the parport driver, and uses direct I/O access instead. This might be +preferred on embedded systems where wasting memory for the clean but heavy +parport handling is not an option. The drawback is a reduced portability +and the impossibility to daisy-chain other parallel port devices. + +Please see i2c-parport for documentation. + +Module parameters: + +* type: type of adapter (see i2c-parport or modinfo) + +* base: base I/O address + Default is 0x378 which is fairly common for parallel ports, at least on PC. + +* irq: optional IRQ + This must be passed if you want SMBus alert support, assuming your adapter + actually supports this. diff --git a/Documentation/i2c/busses/i2c-pca-isa b/Documentation/i2c/busses/i2c-pca-isa new file mode 100644 index 000000000..b044e5265 --- /dev/null +++ b/Documentation/i2c/busses/i2c-pca-isa @@ -0,0 +1,23 @@ +Kernel driver i2c-pca-isa + +Supported adapters: +This driver supports ISA boards using the Philips PCA 9564 +Parallel bus to I2C bus controller + +Author: Ian Campbell <icampbell@arcom.com>, Arcom Control Systems + +Module Parameters +----------------- + +* base int + I/O base address +* irq int + IRQ interrupt +* clock int + Clock rate as described in table 1 of PCA9564 datasheet + +Description +----------- + +This driver supports ISA boards using the Philips PCA 9564 +Parallel bus to I2C bus controller diff --git a/Documentation/i2c/busses/i2c-piix4 b/Documentation/i2c/busses/i2c-piix4 new file mode 100644 index 000000000..aa959fd22 --- /dev/null +++ b/Documentation/i2c/busses/i2c-piix4 @@ -0,0 +1,110 @@ +Kernel driver i2c-piix4 + +Supported adapters: + * Intel 82371AB PIIX4 and PIIX4E + * Intel 82443MX (440MX) + Datasheet: Publicly available at the Intel website + * ServerWorks OSB4, CSB5, CSB6, HT-1000 and HT-1100 southbridges + Datasheet: Only available via NDA from ServerWorks + * ATI IXP200, IXP300, IXP400, SB600, SB700 and SB800 southbridges + Datasheet: Not publicly available + SB700 register reference available at: + http://support.amd.com/us/Embedded_TechDocs/43009_sb7xx_rrg_pub_1.00.pdf + * AMD SP5100 (SB700 derivative found on some server mainboards) + Datasheet: Publicly available at the AMD website + http://support.amd.com/us/Embedded_TechDocs/44413.pdf + * AMD Hudson-2, ML, CZ + Datasheet: Not publicly available + * Standard Microsystems (SMSC) SLC90E66 (Victory66) southbridge + Datasheet: Publicly available at the SMSC website http://www.smsc.com + +Authors: + Frodo Looijaard <frodol@dds.nl> + Philip Edelbrock <phil@netroedge.com> + + +Module Parameters +----------------- + +* force: int + Forcibly enable the PIIX4. DANGEROUS! +* force_addr: int + Forcibly enable the PIIX4 at the given address. EXTREMELY DANGEROUS! + + +Description +----------- + +The PIIX4 (properly known as the 82371AB) is an Intel chip with a lot of +functionality. Among other things, it implements the PCI bus. One of its +minor functions is implementing a System Management Bus. This is a true +SMBus - you can not access it on I2C levels. The good news is that it +natively understands SMBus commands and you do not have to worry about +timing problems. The bad news is that non-SMBus devices connected to it can +confuse it mightily. Yes, this is known to happen... + +Do 'lspci -v' and see whether it contains an entry like this: + +0000:00:02.3 Bridge: Intel Corp. 82371AB/EB/MB PIIX4 ACPI (rev 02) + Flags: medium devsel, IRQ 9 + +Bus and device numbers may differ, but the function number must be +identical (like many PCI devices, the PIIX4 incorporates a number of +different 'functions', which can be considered as separate devices). If you +find such an entry, you have a PIIX4 SMBus controller. + +On some computers (most notably, some Dells), the SMBus is disabled by +default. If you use the insmod parameter 'force=1', the kernel module will +try to enable it. THIS IS VERY DANGEROUS! If the BIOS did not set up a +correct address for this module, you could get in big trouble (read: +crashes, data corruption, etc.). Try this only as a last resort (try BIOS +updates first, for example), and backup first! An even more dangerous +option is 'force_addr=<IOPORT>'. This will not only enable the PIIX4 like +'force' foes, but it will also set a new base I/O port address. The SMBus +parts of the PIIX4 needs a range of 8 of these addresses to function +correctly. If these addresses are already reserved by some other device, +you will get into big trouble! DON'T USE THIS IF YOU ARE NOT VERY SURE +ABOUT WHAT YOU ARE DOING! + +The PIIX4E is just an new version of the PIIX4; it is supported as well. +The PIIX/PIIX3 does not implement an SMBus or I2C bus, so you can't use +this driver on those mainboards. + +The ServerWorks Southbridges, the Intel 440MX, and the Victory66 are +identical to the PIIX4 in I2C/SMBus support. + +The AMD SB700, SB800, SP5100 and Hudson-2 chipsets implement two +PIIX4-compatible SMBus controllers. If your BIOS initializes the +secondary controller, it will be detected by this driver as +an "Auxiliary SMBus Host Controller". + +If you own Force CPCI735 motherboard or other OSB4 based systems you may need +to change the SMBus Interrupt Select register so the SMBus controller uses +the SMI mode. + +1) Use lspci command and locate the PCI device with the SMBus controller: + 00:0f.0 ISA bridge: ServerWorks OSB4 South Bridge (rev 4f) + The line may vary for different chipsets. Please consult the driver source + for all possible PCI ids (and lspci -n to match them). Lets assume the + device is located at 00:0f.0. +2) Now you just need to change the value in 0xD2 register. Get it first with + command: lspci -xxx -s 00:0f.0 + If the value is 0x3 then you need to change it to 0x1 + setpci -s 00:0f.0 d2.b=1 + +Please note that you don't need to do that in all cases, just when the SMBus is +not working properly. + + +Hardware-specific issues +------------------------ + +This driver will refuse to load on IBM systems with an Intel PIIX4 SMBus. +Some of these machines have an RFID EEPROM (24RF08) connected to the SMBus, +which can easily get corrupted due to a state machine bug. These are mostly +Thinkpad laptops, but desktop systems may also be affected. We have no list +of all affected systems, so the only safe solution was to prevent access to +the SMBus on all IBM systems (detected using DMI data.) + +For additional information, read: +http://www.lm-sensors.org/browser/lm-sensors/trunk/README diff --git a/Documentation/i2c/busses/i2c-sis5595 b/Documentation/i2c/busses/i2c-sis5595 new file mode 100644 index 000000000..ecd21fb49 --- /dev/null +++ b/Documentation/i2c/busses/i2c-sis5595 @@ -0,0 +1,59 @@ +Kernel driver i2c-sis5595 + +Authors: + Frodo Looijaard <frodol@dds.nl>, + Mark D. Studebaker <mdsxyz123@yahoo.com>, + Philip Edelbrock <phil@netroedge.com> + +Supported adapters: + * Silicon Integrated Systems Corp. SiS5595 Southbridge + Datasheet: Publicly available at the Silicon Integrated Systems Corp. site. + +Note: all have mfr. ID 0x1039. + + SUPPORTED PCI ID + 5595 0008 + + Note: these chips contain a 0008 device which is incompatible with the + 5595. We recognize these by the presence of the listed + "blacklist" PCI ID and refuse to load. + + NOT SUPPORTED PCI ID BLACKLIST PCI ID + 540 0008 0540 + 550 0008 0550 + 5513 0008 5511 + 5581 0008 5597 + 5582 0008 5597 + 5597 0008 5597 + 5598 0008 5597/5598 + 630 0008 0630 + 645 0008 0645 + 646 0008 0646 + 648 0008 0648 + 650 0008 0650 + 651 0008 0651 + 730 0008 0730 + 735 0008 0735 + 745 0008 0745 + 746 0008 0746 + +Module Parameters +----------------- + +* force_addr=0xaddr Set the I/O base address. Useful for boards + that don't set the address in the BIOS. Does not do a + PCI force; the device must still be present in lspci. + Don't use this unless the driver complains that the + base address is not set. + +Description +----------- + +i2c-sis5595 is a true SMBus host driver for motherboards with the SiS5595 +southbridges. + +WARNING: If you are trying to access the integrated sensors on the SiS5595 +chip, you want the sis5595 driver for those, not this driver. This driver +is a BUS driver, not a CHIP driver. A BUS driver is used by other CHIP +drivers to access chips on the bus. + diff --git a/Documentation/i2c/busses/i2c-sis630 b/Documentation/i2c/busses/i2c-sis630 new file mode 100644 index 000000000..ee7943631 --- /dev/null +++ b/Documentation/i2c/busses/i2c-sis630 @@ -0,0 +1,58 @@ +Kernel driver i2c-sis630 + +Supported adapters: + * Silicon Integrated Systems Corp (SiS) + 630 chipset (Datasheet: available at http://www.sfr-fresh.com/linux) + 730 chipset + 964 chipset + * Possible other SiS chipsets ? + +Author: Alexander Malysh <amalysh@web.de> + Amaury Decrême <amaury.decreme@gmail.com> - SiS964 support + +Module Parameters +----------------- + +* force = [1|0] Forcibly enable the SIS630. DANGEROUS! + This can be interesting for chipsets not named + above to check if it works for you chipset, but DANGEROUS! + +* high_clock = [1|0] Forcibly set Host Master Clock to 56KHz (default, + what your BIOS use). DANGEROUS! This should be a bit + faster, but freeze some systems (i.e. my Laptop). + SIS630/730 chip only. + + +Description +----------- + +This SMBus only driver is known to work on motherboards with the above +named chipsets. + +If you see something like this: + +00:00.0 Host bridge: Silicon Integrated Systems [SiS] 630 Host (rev 31) +00:01.0 ISA bridge: Silicon Integrated Systems [SiS] 85C503/5513 + +or like this: + +00:00.0 Host bridge: Silicon Integrated Systems [SiS] 730 Host (rev 02) +00:01.0 ISA bridge: Silicon Integrated Systems [SiS] 85C503/5513 + +or like this: + +00:00.0 Host bridge: Silicon Integrated Systems [SiS] 760/M760 Host (rev 02) +00:02.0 ISA bridge: Silicon Integrated Systems [SiS] SiS964 [MuTIOL Media IO] + LPC Controller (rev 36) + +in your 'lspci' output , then this driver is for your chipset. + +Thank You +--------- +Philip Edelbrock <phil@netroedge.com> +- testing SiS730 support +Mark M. Hoffman <mhoffman@lightlink.com> +- bug fixes + +To anyone else which I forgot here ;), thanks! + diff --git a/Documentation/i2c/busses/i2c-sis96x b/Documentation/i2c/busses/i2c-sis96x new file mode 100644 index 000000000..0b979f325 --- /dev/null +++ b/Documentation/i2c/busses/i2c-sis96x @@ -0,0 +1,73 @@ +Kernel driver i2c-sis96x + +Replaces 2.4.x i2c-sis645 + +Supported adapters: + * Silicon Integrated Systems Corp (SiS) + Any combination of these host bridges: + 645, 645DX (aka 646), 648, 650, 651, 655, 735, 745, 746 + and these south bridges: + 961, 962, 963(L) + +Author: Mark M. Hoffman <mhoffman@lightlink.com> + +Description +----------- + +This SMBus only driver is known to work on motherboards with the above +named chipset combinations. The driver was developed without benefit of a +proper datasheet from SiS. The SMBus registers are assumed compatible with +those of the SiS630, although they are located in a completely different +place. Thanks to Alexander Malysh <amalysh@web.de> for providing the +SiS630 datasheet (and driver). + +The command "lspci" as root should produce something like these lines: + +00:00.0 Host bridge: Silicon Integrated Systems [SiS]: Unknown device 0645 +00:02.0 ISA bridge: Silicon Integrated Systems [SiS] 85C503/5513 +00:02.1 SMBus: Silicon Integrated Systems [SiS]: Unknown device 0016 + +or perhaps this... + +00:00.0 Host bridge: Silicon Integrated Systems [SiS]: Unknown device 0645 +00:02.0 ISA bridge: Silicon Integrated Systems [SiS]: Unknown device 0961 +00:02.1 SMBus: Silicon Integrated Systems [SiS]: Unknown device 0016 + +(kernel versions later than 2.4.18 may fill in the "Unknown"s) + +If you can't see it please look on quirk_sis_96x_smbus +(drivers/pci/quirks.c) (also if southbridge detection fails) + +I suspect that this driver could be made to work for the following SiS +chipsets as well: 635, and 635T. If anyone owns a board with those chips +AND is willing to risk crashing & burning an otherwise well-behaved kernel +in the name of progress... please contact me at <mhoffman@lightlink.com> or +via the linux-i2c mailing list: <linux-i2c@vger.kernel.org>. Please send bug +reports and/or success stories as well. + + +TO DOs +------ + +* The driver does not support SMBus block reads/writes; I may add them if a +scenario is found where they're needed. + + +Thank You +--------- + +Mark D. Studebaker <mdsxyz123@yahoo.com> + - design hints and bug fixes +Alexander Maylsh <amalysh@web.de> + - ditto, plus an important datasheet... almost the one I really wanted +Hans-Günter Lütke Uphues <hg_lu@t-online.de> + - patch for SiS735 +Robert Zwerus <arzie@dds.nl> + - testing for SiS645DX +Kianusch Sayah Karadji <kianusch@sk-tech.net> + - patch for SiS645DX/962 +Ken Healy + - patch for SiS655 + +To anyone else who has written w/ feedback, thanks! + diff --git a/Documentation/i2c/busses/i2c-taos-evm b/Documentation/i2c/busses/i2c-taos-evm new file mode 100644 index 000000000..60299555d --- /dev/null +++ b/Documentation/i2c/busses/i2c-taos-evm @@ -0,0 +1,46 @@ +Kernel driver i2c-taos-evm + +Author: Jean Delvare <jdelvare@suse.de> + +This is a driver for the evaluation modules for TAOS I2C/SMBus chips. +The modules include an SMBus master with limited capabilities, which can +be controlled over the serial port. Virtually all evaluation modules +are supported, but a few lines of code need to be added for each new +module to instantiate the right I2C chip on the bus. Obviously, a driver +for the chip in question is also needed. + +Currently supported devices are: + +* TAOS TSL2550 EVM + +For additional information on TAOS products, please see + http://www.taosinc.com/ + + +Using this driver +----------------- + +In order to use this driver, you'll need the serport driver, and the +inputattach tool, which is part of the input-utils package. The following +commands will tell the kernel that you have a TAOS EVM on the first +serial port: + +# modprobe serport +# inputattach --taos-evm /dev/ttyS0 + + +Technical details +----------------- + +Only 4 SMBus transaction types are supported by the TAOS evaluation +modules: +* Receive Byte +* Send Byte +* Read Byte +* Write Byte + +The communication protocol is text-based and pretty simple. It is +described in a PDF document on the CD which comes with the evaluation +module. The communication is rather slow, because the serial port has +to operate at 1200 bps. However, I don't think this is a big concern in +practice, as these modules are meant for evaluation and testing only. diff --git a/Documentation/i2c/busses/i2c-via b/Documentation/i2c/busses/i2c-via new file mode 100644 index 000000000..343870661 --- /dev/null +++ b/Documentation/i2c/busses/i2c-via @@ -0,0 +1,34 @@ +Kernel driver i2c-via + +Supported adapters: + * VIA Technologies, InC. VT82C586B + Datasheet: Publicly available at the VIA website + +Author: Kyösti Mälkki <kmalkki@cc.hut.fi> + +Description +----------- + +i2c-via is an i2c bus driver for motherboards with VIA chipset. + +The following VIA pci chipsets are supported: + - MVP3, VP3, VP2/97, VPX/97 + - others with South bridge VT82C586B + +Your lspci listing must show this : + + Bridge: VIA Technologies, Inc. VT82C586B ACPI (rev 10) + + Problems? + + Q: You have VT82C586B on the motherboard, but not in the listing. + + A: Go to your BIOS setup, section PCI devices or similar. + Turn USB support on, and try again. + + Q: No error messages, but still i2c doesn't seem to work. + + A: This can happen. This driver uses the pins VIA recommends in their + datasheets, but there are several ways the motherboard manufacturer + can actually wire the lines. + diff --git a/Documentation/i2c/busses/i2c-viapro b/Documentation/i2c/busses/i2c-viapro new file mode 100644 index 000000000..ab64ce21c --- /dev/null +++ b/Documentation/i2c/busses/i2c-viapro @@ -0,0 +1,73 @@ +Kernel driver i2c-viapro + +Supported adapters: + * VIA Technologies, Inc. VT82C596A/B + Datasheet: Sometimes available at the VIA website + + * VIA Technologies, Inc. VT82C686A/B + Datasheet: Sometimes available at the VIA website + + * VIA Technologies, Inc. VT8231, VT8233, VT8233A + Datasheet: available on request from VIA + + * VIA Technologies, Inc. VT8235, VT8237R, VT8237A, VT8237S, VT8251 + Datasheet: available on request and under NDA from VIA + + * VIA Technologies, Inc. CX700 + Datasheet: available on request and under NDA from VIA + + * VIA Technologies, Inc. VX800/VX820 + Datasheet: available on http://linux.via.com.tw + + * VIA Technologies, Inc. VX855/VX875 + Datasheet: available on http://linux.via.com.tw + + * VIA Technologies, Inc. VX900 + Datasheet: available on http://linux.via.com.tw + +Authors: + Kyösti Mälkki <kmalkki@cc.hut.fi>, + Mark D. Studebaker <mdsxyz123@yahoo.com>, + Jean Delvare <jdelvare@suse.de> + +Module Parameters +----------------- + +* force: int + Forcibly enable the SMBus controller. DANGEROUS! +* force_addr: int + Forcibly enable the SMBus at the given address. EXTREMELY DANGEROUS! + +Description +----------- + +i2c-viapro is a true SMBus host driver for motherboards with one of the +supported VIA south bridges. + +Your lspci -n listing must show one of these : + + device 1106:3050 (VT82C596A function 3) + device 1106:3051 (VT82C596B function 3) + device 1106:3057 (VT82C686 function 4) + device 1106:3074 (VT8233) + device 1106:3147 (VT8233A) + device 1106:8235 (VT8231 function 4) + device 1106:3177 (VT8235) + device 1106:3227 (VT8237R) + device 1106:3337 (VT8237A) + device 1106:3372 (VT8237S) + device 1106:3287 (VT8251) + device 1106:8324 (CX700) + device 1106:8353 (VX800/VX820) + device 1106:8409 (VX855/VX875) + device 1106:8410 (VX900) + +If none of these show up, you should look in the BIOS for settings like +enable ACPI / SMBus or even USB. + +Except for the oldest chips (VT82C596A/B, VT82C686A and most probably +VT8231), this driver supports I2C block transactions. Such transactions +are mainly useful to read from and write to EEPROMs. + +The CX700/VX800/VX820 additionally appears to support SMBus PEC, although +this driver doesn't implement it yet. diff --git a/Documentation/i2c/busses/scx200_acb b/Documentation/i2c/busses/scx200_acb new file mode 100644 index 000000000..ce83c871f --- /dev/null +++ b/Documentation/i2c/busses/scx200_acb @@ -0,0 +1,32 @@ +Kernel driver scx200_acb + +Author: Christer Weinigel <wingel@nano-system.com> + +The driver supersedes the older, never merged driver named i2c-nscacb. + +Module Parameters +----------------- + +* base: up to 4 ints + Base addresses for the ACCESS.bus controllers on SCx200 and SC1100 devices + + By default the driver uses two base addresses 0x820 and 0x840. + If you want only one base address, specify the second as 0 so as to + override this default. + +Description +----------- + +Enable the use of the ACCESS.bus controller on the Geode SCx200 and +SC1100 processors and the CS5535 and CS5536 Geode companion devices. + +Device-specific notes +--------------------- + +The SC1100 WRAP boards are known to use base addresses 0x810 and 0x820. +If the scx200_acb driver is built into the kernel, add the following +parameter to your boot command line: + scx200_acb.base=0x810,0x820 +If the scx200_acb driver is built as a module, add the following line to +a configuration file in /etc/modprobe.d/ instead: + options scx200_acb base=0x810,0x820 diff --git a/Documentation/i2c/dev-interface b/Documentation/i2c/dev-interface new file mode 100644 index 000000000..2ac78ae10 --- /dev/null +++ b/Documentation/i2c/dev-interface @@ -0,0 +1,214 @@ +Usually, i2c devices are controlled by a kernel driver. But it is also +possible to access all devices on an adapter from userspace, through +the /dev interface. You need to load module i2c-dev for this. + +Each registered i2c adapter gets a number, counting from 0. You can +examine /sys/class/i2c-dev/ to see what number corresponds to which adapter. +Alternatively, you can run "i2cdetect -l" to obtain a formated list of all +i2c adapters present on your system at a given time. i2cdetect is part of +the i2c-tools package. + +I2C device files are character device files with major device number 89 +and a minor device number corresponding to the number assigned as +explained above. They should be called "i2c-%d" (i2c-0, i2c-1, ..., +i2c-10, ...). All 256 minor device numbers are reserved for i2c. + + +C example +========= + +So let's say you want to access an i2c adapter from a C program. The +first thing to do is "#include <linux/i2c-dev.h>". Please note that +there are two files named "i2c-dev.h" out there, one is distributed +with the Linux kernel and is meant to be included from kernel +driver code, the other one is distributed with i2c-tools and is +meant to be included from user-space programs. You obviously want +the second one here. + +Now, you have to decide which adapter you want to access. You should +inspect /sys/class/i2c-dev/ or run "i2cdetect -l" to decide this. +Adapter numbers are assigned somewhat dynamically, so you can not +assume much about them. They can even change from one boot to the next. + +Next thing, open the device file, as follows: + + int file; + int adapter_nr = 2; /* probably dynamically determined */ + char filename[20]; + + snprintf(filename, 19, "/dev/i2c-%d", adapter_nr); + file = open(filename, O_RDWR); + if (file < 0) { + /* ERROR HANDLING; you can check errno to see what went wrong */ + exit(1); + } + +When you have opened the device, you must specify with what device +address you want to communicate: + + int addr = 0x40; /* The I2C address */ + + if (ioctl(file, I2C_SLAVE, addr) < 0) { + /* ERROR HANDLING; you can check errno to see what went wrong */ + exit(1); + } + +Well, you are all set up now. You can now use SMBus commands or plain +I2C to communicate with your device. SMBus commands are preferred if +the device supports them. Both are illustrated below. + + __u8 reg = 0x10; /* Device register to access */ + __s32 res; + char buf[10]; + + /* Using SMBus commands */ + res = i2c_smbus_read_word_data(file, reg); + if (res < 0) { + /* ERROR HANDLING: i2c transaction failed */ + } else { + /* res contains the read word */ + } + + /* Using I2C Write, equivalent of + i2c_smbus_write_word_data(file, reg, 0x6543) */ + buf[0] = reg; + buf[1] = 0x43; + buf[2] = 0x65; + if (write(file, buf, 3) != 3) { + /* ERROR HANDLING: i2c transaction failed */ + } + + /* Using I2C Read, equivalent of i2c_smbus_read_byte(file) */ + if (read(file, buf, 1) != 1) { + /* ERROR HANDLING: i2c transaction failed */ + } else { + /* buf[0] contains the read byte */ + } + +Note that only a subset of the I2C and SMBus protocols can be achieved by +the means of read() and write() calls. In particular, so-called combined +transactions (mixing read and write messages in the same transaction) +aren't supported. For this reason, this interface is almost never used by +user-space programs. + +IMPORTANT: because of the use of inline functions, you *have* to use +'-O' or some variation when you compile your program! + + +Full interface description +========================== + +The following IOCTLs are defined: + +ioctl(file, I2C_SLAVE, long addr) + Change slave address. The address is passed in the 7 lower bits of the + argument (except for 10 bit addresses, passed in the 10 lower bits in this + case). + +ioctl(file, I2C_TENBIT, long select) + Selects ten bit addresses if select not equals 0, selects normal 7 bit + addresses if select equals 0. Default 0. This request is only valid + if the adapter has I2C_FUNC_10BIT_ADDR. + +ioctl(file, I2C_PEC, long select) + Selects SMBus PEC (packet error checking) generation and verification + if select not equals 0, disables if select equals 0. Default 0. + Used only for SMBus transactions. This request only has an effect if the + the adapter has I2C_FUNC_SMBUS_PEC; it is still safe if not, it just + doesn't have any effect. + +ioctl(file, I2C_FUNCS, unsigned long *funcs) + Gets the adapter functionality and puts it in *funcs. + +ioctl(file, I2C_RDWR, struct i2c_rdwr_ioctl_data *msgset) + Do combined read/write transaction without stop in between. + Only valid if the adapter has I2C_FUNC_I2C. The argument is + a pointer to a + + struct i2c_rdwr_ioctl_data { + struct i2c_msg *msgs; /* ptr to array of simple messages */ + int nmsgs; /* number of messages to exchange */ + } + + The msgs[] themselves contain further pointers into data buffers. + The function will write or read data to or from that buffers depending + on whether the I2C_M_RD flag is set in a particular message or not. + The slave address and whether to use ten bit address mode has to be + set in each message, overriding the values set with the above ioctl's. + +ioctl(file, I2C_SMBUS, struct i2c_smbus_ioctl_data *args) + Not meant to be called directly; instead, use the access functions + below. + +You can do plain i2c transactions by using read(2) and write(2) calls. +You do not need to pass the address byte; instead, set it through +ioctl I2C_SLAVE before you try to access the device. + +You can do SMBus level transactions (see documentation file smbus-protocol +for details) through the following functions: + __s32 i2c_smbus_write_quick(int file, __u8 value); + __s32 i2c_smbus_read_byte(int file); + __s32 i2c_smbus_write_byte(int file, __u8 value); + __s32 i2c_smbus_read_byte_data(int file, __u8 command); + __s32 i2c_smbus_write_byte_data(int file, __u8 command, __u8 value); + __s32 i2c_smbus_read_word_data(int file, __u8 command); + __s32 i2c_smbus_write_word_data(int file, __u8 command, __u16 value); + __s32 i2c_smbus_process_call(int file, __u8 command, __u16 value); + __s32 i2c_smbus_read_block_data(int file, __u8 command, __u8 *values); + __s32 i2c_smbus_write_block_data(int file, __u8 command, __u8 length, + __u8 *values); +All these transactions return -1 on failure; you can read errno to see +what happened. The 'write' transactions return 0 on success; the +'read' transactions return the read value, except for read_block, which +returns the number of values read. The block buffers need not be longer +than 32 bytes. + +The above functions are all inline functions, that resolve to calls to +the i2c_smbus_access function, that on its turn calls a specific ioctl +with the data in a specific format. Read the source code if you +want to know what happens behind the screens. + + +Implementation details +====================== + +For the interested, here's the code flow which happens inside the kernel +when you use the /dev interface to I2C: + +1* Your program opens /dev/i2c-N and calls ioctl() on it, as described in +section "C example" above. + +2* These open() and ioctl() calls are handled by the i2c-dev kernel +driver: see i2c-dev.c:i2cdev_open() and i2c-dev.c:i2cdev_ioctl(), +respectively. You can think of i2c-dev as a generic I2C chip driver +that can be programmed from user-space. + +3* Some ioctl() calls are for administrative tasks and are handled by +i2c-dev directly. Examples include I2C_SLAVE (set the address of the +device you want to access) and I2C_PEC (enable or disable SMBus error +checking on future transactions.) + +4* Other ioctl() calls are converted to in-kernel function calls by +i2c-dev. Examples include I2C_FUNCS, which queries the I2C adapter +functionality using i2c.h:i2c_get_functionality(), and I2C_SMBUS, which +performs an SMBus transaction using i2c-core.c:i2c_smbus_xfer(). + +The i2c-dev driver is responsible for checking all the parameters that +come from user-space for validity. After this point, there is no +difference between these calls that came from user-space through i2c-dev +and calls that would have been performed by kernel I2C chip drivers +directly. This means that I2C bus drivers don't need to implement +anything special to support access from user-space. + +5* These i2c-core.c/i2c.h functions are wrappers to the actual +implementation of your I2C bus driver. Each adapter must declare +callback functions implementing these standard calls. +i2c.h:i2c_get_functionality() calls i2c_adapter.algo->functionality(), +while i2c-core.c:i2c_smbus_xfer() calls either +adapter.algo->smbus_xfer() if it is implemented, or if not, +i2c-core.c:i2c_smbus_xfer_emulated() which in turn calls +i2c_adapter.algo->master_xfer(). + +After your I2C bus driver has processed these requests, execution runs +up the call chain, with almost no processing done, except by i2c-dev to +package the returned data, if any, in suitable format for the ioctl. diff --git a/Documentation/i2c/fault-codes b/Documentation/i2c/fault-codes new file mode 100644 index 000000000..47c25abb7 --- /dev/null +++ b/Documentation/i2c/fault-codes @@ -0,0 +1,124 @@ +This is a summary of the most important conventions for use of fault +codes in the I2C/SMBus stack. + + +A "Fault" is not always an "Error" +---------------------------------- +Not all fault reports imply errors; "page faults" should be a familiar +example. Software often retries idempotent operations after transient +faults. There may be fancier recovery schemes that are appropriate in +some cases, such as re-initializing (and maybe resetting). After such +recovery, triggered by a fault report, there is no error. + +In a similar way, sometimes a "fault" code just reports one defined +result for an operation ... it doesn't indicate that anything is wrong +at all, just that the outcome wasn't on the "golden path". + +In short, your I2C driver code may need to know these codes in order +to respond correctly. Other code may need to rely on YOUR code reporting +the right fault code, so that it can (in turn) behave correctly. + + +I2C and SMBus fault codes +------------------------- +These are returned as negative numbers from most calls, with zero or +some positive number indicating a non-fault return. The specific +numbers associated with these symbols differ between architectures, +though most Linux systems use <asm-generic/errno*.h> numbering. + +Note that the descriptions here are not exhaustive. There are other +codes that may be returned, and other cases where these codes should +be returned. However, drivers should not return other codes for these +cases (unless the hardware doesn't provide unique fault reports). + +Also, codes returned by adapter probe methods follow rules which are +specific to their host bus (such as PCI, or the platform bus). + + +EAGAIN + Returned by I2C adapters when they lose arbitration in master + transmit mode: some other master was transmitting different + data at the same time. + + Also returned when trying to invoke an I2C operation in an + atomic context, when some task is already using that I2C bus + to execute some other operation. + +EBADMSG + Returned by SMBus logic when an invalid Packet Error Code byte + is received. This code is a CRC covering all bytes in the + transaction, and is sent before the terminating STOP. This + fault is only reported on read transactions; the SMBus slave + may have a way to report PEC mismatches on writes from the + host. Note that even if PECs are in use, you should not rely + on these as the only way to detect incorrect data transfers. + +EBUSY + Returned by SMBus adapters when the bus was busy for longer + than allowed. This usually indicates some device (maybe the + SMBus adapter) needs some fault recovery (such as resetting), + or that the reset was attempted but failed. + +EINVAL + This rather vague error means an invalid parameter has been + detected before any I/O operation was started. Use a more + specific fault code when you can. + +EIO + This rather vague error means something went wrong when + performing an I/O operation. Use a more specific fault + code when you can. + +ENODEV + Returned by driver probe() methods. This is a bit more + specific than ENXIO, implying the problem isn't with the + address, but with the device found there. Driver probes + may verify the device returns *correct* responses, and + return this as appropriate. (The driver core will warn + about probe faults other than ENXIO and ENODEV.) + +ENOMEM + Returned by any component that can't allocate memory when + it needs to do so. + +ENXIO + Returned by I2C adapters to indicate that the address phase + of a transfer didn't get an ACK. While it might just mean + an I2C device was temporarily not responding, usually it + means there's nothing listening at that address. + + Returned by driver probe() methods to indicate that they + found no device to bind to. (ENODEV may also be used.) + +EOPNOTSUPP + Returned by an adapter when asked to perform an operation + that it doesn't, or can't, support. + + For example, this would be returned when an adapter that + doesn't support SMBus block transfers is asked to execute + one. In that case, the driver making that request should + have verified that functionality was supported before it + made that block transfer request. + + Similarly, if an I2C adapter can't execute all legal I2C + messages, it should return this when asked to perform a + transaction it can't. (These limitations can't be seen in + the adapter's functionality mask, since the assumption is + that if an adapter supports I2C it supports all of I2C.) + +EPROTO + Returned when slave does not conform to the relevant I2C + or SMBus (or chip-specific) protocol specifications. One + case is when the length of an SMBus block data response + (from the SMBus slave) is outside the range 1-32 bytes. + +ETIMEDOUT + This is returned by drivers when an operation took too much + time, and was aborted before it completed. + + SMBus adapters may return it when an operation took more + time than allowed by the SMBus specification; for example, + when a slave stretches clocks too far. I2C has no such + timeouts, but it's normal for I2C adapters to impose some + arbitrary limits (much longer than SMBus!) too. + diff --git a/Documentation/i2c/functionality b/Documentation/i2c/functionality new file mode 100644 index 000000000..4aae8ed15 --- /dev/null +++ b/Documentation/i2c/functionality @@ -0,0 +1,148 @@ +INTRODUCTION +------------ + +Because not every I2C or SMBus adapter implements everything in the +I2C specifications, a client can not trust that everything it needs +is implemented when it is given the option to attach to an adapter: +the client needs some way to check whether an adapter has the needed +functionality. + + +FUNCTIONALITY CONSTANTS +----------------------- + +For the most up-to-date list of functionality constants, please check +<uapi/linux/i2c.h>! + + I2C_FUNC_I2C Plain i2c-level commands (Pure SMBus + adapters typically can not do these) + I2C_FUNC_10BIT_ADDR Handles the 10-bit address extensions + I2C_FUNC_PROTOCOL_MANGLING Knows about the I2C_M_IGNORE_NAK, + I2C_M_REV_DIR_ADDR and I2C_M_NO_RD_ACK + flags (which modify the I2C protocol!) + I2C_FUNC_NOSTART Can skip repeated start sequence + I2C_FUNC_SMBUS_QUICK Handles the SMBus write_quick command + I2C_FUNC_SMBUS_READ_BYTE Handles the SMBus read_byte command + I2C_FUNC_SMBUS_WRITE_BYTE Handles the SMBus write_byte command + I2C_FUNC_SMBUS_READ_BYTE_DATA Handles the SMBus read_byte_data command + I2C_FUNC_SMBUS_WRITE_BYTE_DATA Handles the SMBus write_byte_data command + I2C_FUNC_SMBUS_READ_WORD_DATA Handles the SMBus read_word_data command + I2C_FUNC_SMBUS_WRITE_WORD_DATA Handles the SMBus write_byte_data command + I2C_FUNC_SMBUS_PROC_CALL Handles the SMBus process_call command + I2C_FUNC_SMBUS_READ_BLOCK_DATA Handles the SMBus read_block_data command + I2C_FUNC_SMBUS_WRITE_BLOCK_DATA Handles the SMBus write_block_data command + I2C_FUNC_SMBUS_READ_I2C_BLOCK Handles the SMBus read_i2c_block_data command + I2C_FUNC_SMBUS_WRITE_I2C_BLOCK Handles the SMBus write_i2c_block_data command + +A few combinations of the above flags are also defined for your convenience: + + I2C_FUNC_SMBUS_BYTE Handles the SMBus read_byte + and write_byte commands + I2C_FUNC_SMBUS_BYTE_DATA Handles the SMBus read_byte_data + and write_byte_data commands + I2C_FUNC_SMBUS_WORD_DATA Handles the SMBus read_word_data + and write_word_data commands + I2C_FUNC_SMBUS_BLOCK_DATA Handles the SMBus read_block_data + and write_block_data commands + I2C_FUNC_SMBUS_I2C_BLOCK Handles the SMBus read_i2c_block_data + and write_i2c_block_data commands + I2C_FUNC_SMBUS_EMUL Handles all SMBus commands that can be + emulated by a real I2C adapter (using + the transparent emulation layer) + +In kernel versions prior to 3.5 I2C_FUNC_NOSTART was implemented as +part of I2C_FUNC_PROTOCOL_MANGLING. + + +ADAPTER IMPLEMENTATION +---------------------- + +When you write a new adapter driver, you will have to implement a +function callback `functionality'. Typical implementations are given +below. + +A typical SMBus-only adapter would list all the SMBus transactions it +supports. This example comes from the i2c-piix4 driver: + + static u32 piix4_func(struct i2c_adapter *adapter) + { + return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | + I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | + I2C_FUNC_SMBUS_BLOCK_DATA; + } + +A typical full-I2C adapter would use the following (from the i2c-pxa +driver): + + static u32 i2c_pxa_functionality(struct i2c_adapter *adap) + { + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; + } + +I2C_FUNC_SMBUS_EMUL includes all the SMBus transactions (with the +addition of I2C block transactions) which i2c-core can emulate using +I2C_FUNC_I2C without any help from the adapter driver. The idea is +to let the client drivers check for the support of SMBus functions +without having to care whether the said functions are implemented in +hardware by the adapter, or emulated in software by i2c-core on top +of an I2C adapter. + + +CLIENT CHECKING +--------------- + +Before a client tries to attach to an adapter, or even do tests to check +whether one of the devices it supports is present on an adapter, it should +check whether the needed functionality is present. The typical way to do +this is (from the lm75 driver): + + static int lm75_detect(...) + { + (...) + if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA | + I2C_FUNC_SMBUS_WORD_DATA)) + goto exit; + (...) + } + +Here, the lm75 driver checks if the adapter can do both SMBus byte data +and SMBus word data transactions. If not, then the driver won't work on +this adapter and there's no point in going on. If the check above is +successful, then the driver knows that it can call the following +functions: i2c_smbus_read_byte_data(), i2c_smbus_write_byte_data(), +i2c_smbus_read_word_data() and i2c_smbus_write_word_data(). As a rule of +thumb, the functionality constants you test for with +i2c_check_functionality() should match exactly the i2c_smbus_* functions +which you driver is calling. + +Note that the check above doesn't tell whether the functionalities are +implemented in hardware by the underlying adapter or emulated in +software by i2c-core. Client drivers don't have to care about this, as +i2c-core will transparently implement SMBus transactions on top of I2C +adapters. + + +CHECKING THROUGH /DEV +--------------------- + +If you try to access an adapter from a userspace program, you will have +to use the /dev interface. You will still have to check whether the +functionality you need is supported, of course. This is done using +the I2C_FUNCS ioctl. An example, adapted from the i2cdetect program, is +below: + + int file; + if (file = open("/dev/i2c-0", O_RDWR) < 0) { + /* Some kind of error handling */ + exit(1); + } + if (ioctl(file, I2C_FUNCS, &funcs) < 0) { + /* Some kind of error handling */ + exit(1); + } + if (!(funcs & I2C_FUNC_SMBUS_QUICK)) { + /* Oops, the needed functionality (SMBus write_quick function) is + not available! */ + exit(1); + } + /* Now it is safe to use the SMBus write_quick command */ diff --git a/Documentation/i2c/i2c-protocol b/Documentation/i2c/i2c-protocol new file mode 100644 index 000000000..ff6d6cee6 --- /dev/null +++ b/Documentation/i2c/i2c-protocol @@ -0,0 +1,88 @@ +This document describes the i2c protocol. Or will, when it is finished :-) + +Key to symbols +============== + +S (1 bit) : Start bit +P (1 bit) : Stop bit +Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0. +A, NA (1 bit) : Accept and reverse accept bit. +Addr (7 bits): I2C 7 bit address. Note that this can be expanded as usual to + get a 10 bit I2C address. +Comm (8 bits): Command byte, a data byte which often selects a register on + the device. +Data (8 bits): A plain data byte. Sometimes, I write DataLow, DataHigh + for 16 bit data. +Count (8 bits): A data byte containing the length of a block operation. + +[..]: Data sent by I2C device, as opposed to data sent by the host adapter. + + +Simple send transaction +====================== + +This corresponds to i2c_master_send. + + S Addr Wr [A] Data [A] Data [A] ... [A] Data [A] P + + +Simple receive transaction +=========================== + +This corresponds to i2c_master_recv + + S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P + + +Combined transactions +==================== + +This corresponds to i2c_transfer + +They are just like the above transactions, but instead of a stop bit P +a start bit S is sent and the transaction continues. An example of +a byte read, followed by a byte write: + + S Addr Rd [A] [Data] NA S Addr Wr [A] Data [A] P + + +Modified transactions +===================== + +The following modifications to the I2C protocol can also be generated by +setting these flags for i2c messages. With the exception of I2C_M_NOSTART, they +are usually only needed to work around device issues: + +I2C_M_IGNORE_NAK: + Normally message is interrupted immediately if there is [NA] from the + client. Setting this flag treats any [NA] as [A], and all of + message is sent. + These messages may still fail to SCL lo->hi timeout. + +I2C_M_NO_RD_ACK: + In a read message, master A/NA bit is skipped. + +I2C_M_NOSTART: + In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some + point. For example, setting I2C_M_NOSTART on the second partial message + generates something like: + S Addr Rd [A] [Data] NA Data [A] P + If you set the I2C_M_NOSTART variable for the first partial message, + we do not generate Addr, but we do generate the startbit S. This will + probably confuse all other clients on your bus, so don't try this. + + This is often used to gather transmits from multiple data buffers in + system memory into something that appears as a single transfer to the + I2C device but may also be used between direction changes by some + rare devices. + +I2C_M_REV_DIR_ADDR: + This toggles the Rd/Wr flag. That is, if you want to do a write, but + need to emit an Rd instead of a Wr, or vice versa, you set this + flag. For example: + S Addr Rd [A] Data [A] Data [A] ... [A] Data [A] P + +I2C_M_STOP: + Force a stop condition (P) after the message. Some I2C related protocols + like SCCB require that. Normally, you really don't want to get interrupted + between the messages of one transfer. diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub new file mode 100644 index 000000000..a16924fbd --- /dev/null +++ b/Documentation/i2c/i2c-stub @@ -0,0 +1,64 @@ +MODULE: i2c-stub + +DESCRIPTION: + +This module is a very simple fake I2C/SMBus driver. It implements six +types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w) +word data, (r/w) I2C block data, and (r/w) SMBus block data. + +You need to provide chip addresses as a module parameter when loading this +driver, which will then only react to SMBus commands to these addresses. + +No hardware is needed nor associated with this module. It will accept write +quick commands to the specified addresses; it will respond to the other +commands (also to the specified addresses) by reading from or writing to +arrays in memory. It will also spam the kernel logs for every command it +handles. + +A pointer register with auto-increment is implemented for all byte +operations. This allows for continuous byte reads like those supported by +EEPROMs, among others. + +SMBus block command support is disabled by default, and must be enabled +explicitly by setting the respective bits (0x03000000) in the functionality +module parameter. + +SMBus block commands must be written to configure an SMBus command for +SMBus block operations. Writes can be partial. Block read commands always +return the number of bytes selected with the largest write so far. + +The typical use-case is like this: + 1. load this module + 2. use i2cset (from the i2c-tools project) to pre-load some data + 3. load the target chip driver module + 4. observe its behavior in the kernel log + +There's a script named i2c-stub-from-dump in the i2c-tools package which +can load register values automatically from a chip dump. + +PARAMETERS: + +int chip_addr[10]: + The SMBus addresses to emulate chips at. + +unsigned long functionality: + Functionality override, to disable some commands. See I2C_FUNC_* + constants in <linux/i2c.h> for the suitable values. For example, + value 0x1f0000 would only enable the quick, byte and byte data + commands. + +u8 bank_reg[10] +u8 bank_mask[10] +u8 bank_start[10] +u8 bank_end[10]: + Optional bank settings. They tell which bits in which register + select the active bank, as well as the range of banked registers. + +CAVEATS: + +If your target driver polls some byte or word waiting for it to change, the +stub could lock it up. Use i2cset to unlock it. + +If you spam it hard enough, printk can be lossy. This module really wants +something like relayfs. + diff --git a/Documentation/i2c/instantiating-devices b/Documentation/i2c/instantiating-devices new file mode 100644 index 000000000..0d85ac193 --- /dev/null +++ b/Documentation/i2c/instantiating-devices @@ -0,0 +1,248 @@ +How to instantiate I2C devices +============================== + +Unlike PCI or USB devices, I2C devices are not enumerated at the hardware +level. Instead, the software must know which devices are connected on each +I2C bus segment, and what address these devices are using. For this +reason, the kernel code must instantiate I2C devices explicitly. There are +several ways to achieve this, depending on the context and requirements. + + +Method 1a: Declare the I2C devices by bus number +------------------------------------------------ + +This method is appropriate when the I2C bus is a system bus as is the case +for many embedded systems. On such systems, each I2C bus has a number +which is known in advance. It is thus possible to pre-declare the I2C +devices which live on this bus. This is done with an array of struct +i2c_board_info which is registered by calling i2c_register_board_info(). + +Example (from omap2 h4): + +static struct i2c_board_info h4_i2c_board_info[] __initdata = { + { + I2C_BOARD_INFO("isp1301_omap", 0x2d), + .irq = OMAP_GPIO_IRQ(125), + }, + { /* EEPROM on mainboard */ + I2C_BOARD_INFO("24c01", 0x52), + .platform_data = &m24c01, + }, + { /* EEPROM on cpu card */ + I2C_BOARD_INFO("24c01", 0x57), + .platform_data = &m24c01, + }, +}; + +static void __init omap_h4_init(void) +{ + (...) + i2c_register_board_info(1, h4_i2c_board_info, + ARRAY_SIZE(h4_i2c_board_info)); + (...) +} + +The above code declares 3 devices on I2C bus 1, including their respective +addresses and custom data needed by their drivers. When the I2C bus in +question is registered, the I2C devices will be instantiated automatically +by i2c-core. + +The devices will be automatically unbound and destroyed when the I2C bus +they sit on goes away (if ever.) + + +Method 1b: Declare the I2C devices via devicetree +------------------------------------------------- + +This method has the same implications as method 1a. The declaration of I2C +devices is here done via devicetree as subnodes of the master controller. + +Example: + + i2c1: i2c@400a0000 { + /* ... master properties skipped ... */ + clock-frequency = <100000>; + + flash@50 { + compatible = "atmel,24c256"; + reg = <0x50>; + }; + + pca9532: gpio@60 { + compatible = "nxp,pca9532"; + gpio-controller; + #gpio-cells = <2>; + reg = <0x60>; + }; + }; + +Here, two devices are attached to the bus using a speed of 100kHz. For +additional properties which might be needed to set up the device, please refer +to its devicetree documentation in Documentation/devicetree/bindings/. + + +Method 1c: Declare the I2C devices via ACPI +------------------------------------------- + +ACPI can also describe I2C devices. There is special documentation for this +which is currently located at Documentation/acpi/enumeration.txt. + + +Method 2: Instantiate the devices explicitly +-------------------------------------------- + +This method is appropriate when a larger device uses an I2C bus for +internal communication. A typical case is TV adapters. These can have a +tuner, a video decoder, an audio decoder, etc. usually connected to the +main chip by the means of an I2C bus. You won't know the number of the I2C +bus in advance, so the method 1 described above can't be used. Instead, +you can instantiate your I2C devices explicitly. This is done by filling +a struct i2c_board_info and calling i2c_new_device(). + +Example (from the sfe4001 network driver): + +static struct i2c_board_info sfe4001_hwmon_info = { + I2C_BOARD_INFO("max6647", 0x4e), +}; + +int sfe4001_init(struct efx_nic *efx) +{ + (...) + efx->board_info.hwmon_client = + i2c_new_device(&efx->i2c_adap, &sfe4001_hwmon_info); + + (...) +} + +The above code instantiates 1 I2C device on the I2C bus which is on the +network adapter in question. + +A variant of this is when you don't know for sure if an I2C device is +present or not (for example for an optional feature which is not present +on cheap variants of a board but you have no way to tell them apart), or +it may have different addresses from one board to the next (manufacturer +changing its design without notice). In this case, you can call +i2c_new_probed_device() instead of i2c_new_device(). + +Example (from the nxp OHCI driver): + +static const unsigned short normal_i2c[] = { 0x2c, 0x2d, I2C_CLIENT_END }; + +static int usb_hcd_nxp_probe(struct platform_device *pdev) +{ + (...) + struct i2c_adapter *i2c_adap; + struct i2c_board_info i2c_info; + + (...) + i2c_adap = i2c_get_adapter(2); + memset(&i2c_info, 0, sizeof(struct i2c_board_info)); + strlcpy(i2c_info.type, "isp1301_nxp", I2C_NAME_SIZE); + isp1301_i2c_client = i2c_new_probed_device(i2c_adap, &i2c_info, + normal_i2c, NULL); + i2c_put_adapter(i2c_adap); + (...) +} + +The above code instantiates up to 1 I2C device on the I2C bus which is on +the OHCI adapter in question. It first tries at address 0x2c, if nothing +is found there it tries address 0x2d, and if still nothing is found, it +simply gives up. + +The driver which instantiated the I2C device is responsible for destroying +it on cleanup. This is done by calling i2c_unregister_device() on the +pointer that was earlier returned by i2c_new_device() or +i2c_new_probed_device(). + + +Method 3: Probe an I2C bus for certain devices +---------------------------------------------- + +Sometimes you do not have enough information about an I2C device, not even +to call i2c_new_probed_device(). The typical case is hardware monitoring +chips on PC mainboards. There are several dozen models, which can live +at 25 different addresses. Given the huge number of mainboards out there, +it is next to impossible to build an exhaustive list of the hardware +monitoring chips being used. Fortunately, most of these chips have +manufacturer and device ID registers, so they can be identified by +probing. + +In that case, I2C devices are neither declared nor instantiated +explicitly. Instead, i2c-core will probe for such devices as soon as their +drivers are loaded, and if any is found, an I2C device will be +instantiated automatically. In order to prevent any misbehavior of this +mechanism, the following restrictions apply: +* The I2C device driver must implement the detect() method, which + identifies a supported device by reading from arbitrary registers. +* Only buses which are likely to have a supported device and agree to be + probed, will be probed. For example this avoids probing for hardware + monitoring chips on a TV adapter. + +Example: +See lm90_driver and lm90_detect() in drivers/hwmon/lm90.c + +I2C devices instantiated as a result of such a successful probe will be +destroyed automatically when the driver which detected them is removed, +or when the underlying I2C bus is itself destroyed, whichever happens +first. + +Those of you familiar with the i2c subsystem of 2.4 kernels and early 2.6 +kernels will find out that this method 3 is essentially similar to what +was done there. Two significant differences are: +* Probing is only one way to instantiate I2C devices now, while it was the + only way back then. Where possible, methods 1 and 2 should be preferred. + Method 3 should only be used when there is no other way, as it can have + undesirable side effects. +* I2C buses must now explicitly say which I2C driver classes can probe + them (by the means of the class bitfield), while all I2C buses were + probed by default back then. The default is an empty class which means + that no probing happens. The purpose of the class bitfield is to limit + the aforementioned undesirable side effects. + +Once again, method 3 should be avoided wherever possible. Explicit device +instantiation (methods 1 and 2) is much preferred for it is safer and +faster. + + +Method 4: Instantiate from user-space +------------------------------------- + +In general, the kernel should know which I2C devices are connected and +what addresses they live at. However, in certain cases, it does not, so a +sysfs interface was added to let the user provide the information. This +interface is made of 2 attribute files which are created in every I2C bus +directory: new_device and delete_device. Both files are write only and you +must write the right parameters to them in order to properly instantiate, +respectively delete, an I2C device. + +File new_device takes 2 parameters: the name of the I2C device (a string) +and the address of the I2C device (a number, typically expressed in +hexadecimal starting with 0x, but can also be expressed in decimal.) + +File delete_device takes a single parameter: the address of the I2C +device. As no two devices can live at the same address on a given I2C +segment, the address is sufficient to uniquely identify the device to be +deleted. + +Example: +# echo eeprom 0x50 > /sys/bus/i2c/devices/i2c-3/new_device + +While this interface should only be used when in-kernel device declaration +can't be done, there is a variety of cases where it can be helpful: +* The I2C driver usually detects devices (method 3 above) but the bus + segment your device lives on doesn't have the proper class bit set and + thus detection doesn't trigger. +* The I2C driver usually detects devices, but your device lives at an + unexpected address. +* The I2C driver usually detects devices, but your device is not detected, + either because the detection routine is too strict, or because your + device is not officially supported yet but you know it is compatible. +* You are developing a driver on a test board, where you soldered the I2C + device yourself. + +This interface is a replacement for the force_* module parameters some I2C +drivers implement. Being implemented in i2c-core rather than in each +device driver individually, it is much more efficient, and also has the +advantage that you do not have to reload the driver to change a setting. +You can also instantiate the device before the driver is loaded or even +available, and you don't need to know what driver the device needs. diff --git a/Documentation/i2c/muxes/i2c-mux-gpio b/Documentation/i2c/muxes/i2c-mux-gpio new file mode 100644 index 000000000..d4d91a53f --- /dev/null +++ b/Documentation/i2c/muxes/i2c-mux-gpio @@ -0,0 +1,83 @@ +Kernel driver i2c-gpio-mux + +Author: Peter Korsgaard <peter.korsgaard@barco.com> + +Description +----------- + +i2c-gpio-mux is an i2c mux driver providing access to I2C bus segments +from a master I2C bus and a hardware MUX controlled through GPIO pins. + +E.G.: + + ---------- ---------- Bus segment 1 - - - - - + | | SCL/SDA | |-------------- | | + | |------------| | + | | | | Bus segment 2 | | + | Linux | GPIO 1..N | MUX |--------------- Devices + | |------------| | | | + | | | | Bus segment M + | | | |---------------| | + ---------- ---------- - - - - - + +SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M +according to the settings of the GPIO pins 1..N. + +Usage +----- + +i2c-gpio-mux uses the platform bus, so you need to provide a struct +platform_device with the platform_data pointing to a struct +gpio_i2cmux_platform_data with the I2C adapter number of the master +bus, the number of bus segments to create and the GPIO pins used +to control it. See include/linux/i2c-gpio-mux.h for details. + +E.G. something like this for a MUX providing 4 bus segments +controlled through 3 GPIO pins: + +#include <linux/i2c-gpio-mux.h> +#include <linux/platform_device.h> + +static const unsigned myboard_gpiomux_gpios[] = { + AT91_PIN_PC26, AT91_PIN_PC25, AT91_PIN_PC24 +}; + +static const unsigned myboard_gpiomux_values[] = { + 0, 1, 2, 3 +}; + +static struct gpio_i2cmux_platform_data myboard_i2cmux_data = { + .parent = 1, + .base_nr = 2, /* optional */ + .values = myboard_gpiomux_values, + .n_values = ARRAY_SIZE(myboard_gpiomux_values), + .gpios = myboard_gpiomux_gpios, + .n_gpios = ARRAY_SIZE(myboard_gpiomux_gpios), + .idle = 4, /* optional */ +}; + +static struct platform_device myboard_i2cmux = { + .name = "i2c-gpio-mux", + .id = 0, + .dev = { + .platform_data = &myboard_i2cmux_data, + }, +}; + +If you don't know the absolute GPIO pin numbers at registration time, +you can instead provide a chip name (.chip_name) and relative GPIO pin +numbers, and the i2c-gpio-mux driver will do the work for you, +including deferred probing if the GPIO chip isn't immediately +available. + +Device Registration +------------------- + +When registering your i2c-gpio-mux device, you should pass the number +of any GPIO pin it uses as the device ID. This guarantees that every +instance has a different ID. + +Alternatively, if you don't need a stable device name, you can simply +pass PLATFORM_DEVID_AUTO as the device ID, and the platform core will +assign a dynamic ID to your device. If you do not know the absolute +GPIO pin numbers at registration time, this is even the only option. diff --git a/Documentation/i2c/old-module-parameters b/Documentation/i2c/old-module-parameters new file mode 100644 index 000000000..8e2b629d5 --- /dev/null +++ b/Documentation/i2c/old-module-parameters @@ -0,0 +1,44 @@ +I2C device driver binding control from user-space +================================================= + +Up to kernel 2.6.32, many i2c drivers used helper macros provided by +<linux/i2c.h> which created standard module parameters to let the user +control how the driver would probe i2c buses and attach to devices. These +parameters were known as "probe" (to let the driver probe for an extra +address), "force" (to forcibly attach the driver to a given device) and +"ignore" (to prevent a driver from probing a given address). + +With the conversion of the i2c subsystem to the standard device driver +binding model, it became clear that these per-module parameters were no +longer needed, and that a centralized implementation was possible. The new, +sysfs-based interface is described in the documentation file +"instantiating-devices", section "Method 4: Instantiate from user-space". + +Below is a mapping from the old module parameters to the new interface. + +Attaching a driver to an I2C device +----------------------------------- + +Old method (module parameters): +# modprobe <driver> probe=1,0x2d +# modprobe <driver> force=1,0x2d +# modprobe <driver> force_<device>=1,0x2d + +New method (sysfs interface): +# echo <device> 0x2d > /sys/bus/i2c/devices/i2c-1/new_device + +Preventing a driver from attaching to an I2C device +--------------------------------------------------- + +Old method (module parameters): +# modprobe <driver> ignore=1,0x2f + +New method (sysfs interface): +# echo dummy 0x2f > /sys/bus/i2c/devices/i2c-1/new_device +# modprobe <driver> + +Of course, it is important to instantiate the "dummy" device before loading +the driver. The dummy device will be handled by i2c-core itself, preventing +other drivers from binding to it later on. If there is a real device at the +problematic address, and you want another driver to bind to it, then simply +pass the name of the device in question instead of "dummy". diff --git a/Documentation/i2c/slave-eeprom-backend b/Documentation/i2c/slave-eeprom-backend new file mode 100644 index 000000000..c8444ef82 --- /dev/null +++ b/Documentation/i2c/slave-eeprom-backend @@ -0,0 +1,14 @@ +Linux I2C slave eeprom backend +============================== + +by Wolfram Sang <wsa@sang-engineering.com> in 2014-15 + +This is a proof-of-concept backend which acts like an EEPROM on the connected +I2C bus. The memory contents can be modified from userspace via this file +located in sysfs: + + /sys/bus/i2c/devices/<device-direcory>/slave-eeprom + +As of 2015, Linux doesn't support poll on binary sysfs files, so there is no +notfication when another master changed the content. + diff --git a/Documentation/i2c/slave-interface b/Documentation/i2c/slave-interface new file mode 100644 index 000000000..b228ca54b --- /dev/null +++ b/Documentation/i2c/slave-interface @@ -0,0 +1,179 @@ +Linux I2C slave interface description +===================================== + +by Wolfram Sang <wsa@sang-engineering.com> in 2014-15 + +Linux can also be an I2C slave in case I2C controllers have slave support. +Besides this HW requirement, one also needs a software backend providing the +actual functionality. An example for this is the slave-eeprom driver, which +acts as a dual memory driver. While another I2C master on the bus can access it +like a regular EEPROM, the Linux I2C slave can access the content via sysfs and +retrieve/provide information as needed. The software backend driver and the I2C +bus driver communicate via events. Here is a small graph visualizing the data +flow and the means by which data is transported. The dotted line marks only one +example. The backend could also use e.g. a character device, be in-kernel +only, or something completely different: + + + e.g. sysfs I2C slave events I/O registers + +-----------+ v +---------+ v +--------+ v +------------+ + | Userspace +........+ Backend +-----------+ Driver +-----+ Controller | + +-----------+ +---------+ +--------+ +------------+ + | | + ----------------------------------------------------------------+-- I2C + --------------------------------------------------------------+---- Bus + +Note: Technically, there is also the I2C core between the backend and the +driver. However, at this time of writing, the layer is transparent. + + +User manual +=========== + +I2C slave backends behave like standard I2C clients. So, you can instantiate +them as described in the document 'instantiating-devices'. A quick example for +instantiating the slave-eeprom driver from userspace at address 0x64 on bus 1: + + # echo slave-24c02 0x64 > /sys/bus/i2c/devices/i2c-1/new_device + +Each backend should come with separate documentation to describe its specific +behaviour and setup. + + +Developer manual +================ + +I2C slave events +---------------- + +The bus driver sends an event to the backend using the following function: + + ret = i2c_slave_event(client, event, &val) + +'client' describes the i2c slave device. 'event' is one of the special event +types described hereafter. 'val' holds an u8 value for the data byte to be +read/written and is thus bidirectional. The pointer to val must always be +provided even if val is not used for an event, i.e. don't use NULL here. 'ret' +is the return value from the backend. Mandatory events must be provided by the +bus drivers and must be checked for by backend drivers. + +Event types: + +* I2C_SLAVE_WRITE_REQUESTED (mandatory) + +'val': unused +'ret': always 0 + +Another I2C master wants to write data to us. This event should be sent once +our own address and the write bit was detected. The data did not arrive yet, so +there is nothing to process or return. Wakeup or initialization probably needs +to be done, though. + +* I2C_SLAVE_READ_REQUESTED (mandatory) + +'val': backend returns first byte to be sent +'ret': always 0 + +Another I2C master wants to read data from us. This event should be sent once +our own address and the read bit was detected. After returning, the bus driver +should transmit the first byte. + +* I2C_SLAVE_WRITE_RECEIVED (mandatory) + +'val': bus driver delivers received byte +'ret': 0 if the byte should be acked, some errno if the byte should be nacked + +Another I2C master has sent a byte to us which needs to be set in 'val'. If 'ret' +is zero, the bus driver should ack this byte. If 'ret' is an errno, then the byte +should be nacked. + +* I2C_SLAVE_READ_PROCESSED (mandatory) + +'val': backend returns next byte to be sent +'ret': always 0 + +The bus driver requests the next byte to be sent to another I2C master in +'val'. Important: This does not mean that the previous byte has been acked, it +only means that the previous byte is shifted out to the bus! To ensure seamless +transmission, most hardware requests the next byte when the previous one is +still shifted out. If the master sends NACK and stops reading after the byte +currently shifted out, this byte requested here is never used. It very likely +needs to be sent again on the next I2C_SLAVE_READ_REQUEST, depending a bit on +your backend, though. + +* I2C_SLAVE_STOP (mandatory) + +'val': unused +'ret': always 0 + +A stop condition was received. This can happen anytime and the backend should +reset its state machine for I2C transfers to be able to receive new requests. + + +Software backends +----------------- + +If you want to write a software backend: + +* use a standard i2c_driver and its matching mechanisms +* write the slave_callback which handles the above slave events + (best using a state machine) +* register this callback via i2c_slave_register() + +Check the i2c-slave-eeprom driver as an example. + + +Bus driver support +------------------ + +If you want to add slave support to the bus driver: + +* implement calls to register/unregister the slave and add those to the + struct i2c_algorithm. When registering, you probably need to set the i2c + slave address and enable slave specific interrupts. If you use runtime pm, you + should use pm_runtime_forbid() because your device usually needs to be powered + on always to be able to detect its slave address. When unregistering, do the + inverse of the above. + +* Catch the slave interrupts and send appropriate i2c_slave_events to the backend. + +Check the i2c-rcar driver as an example. + + +About ACK/NACK +-------------- + +It is good behaviour to always ACK the address phase, so the master knows if a +device is basically present or if it mysteriously disappeared. Using NACK to +state being busy is troublesome. SMBus demands to always ACK the address phase, +while the I2C specification is more loose on that. Most I2C controllers also +automatically ACK when detecting their slave addresses, so there is no option +to NACK them. For those reasons, this API does not support NACK in the address +phase. + +Currently, there is no slave event to report if the master did ACK or NACK a +byte when it reads from us. We could make this an optional event if the need +arises. However, cases should be extremely rare because the master is expected +to send STOP after that and we have an event for that. Also, keep in mind not +all I2C controllers have the possibility to report that event. + + +About buffers +------------- + +During development of this API, the question of using buffers instead of just +bytes came up. Such an extension might be possible, usefulness is unclear at +this time of writing. Some points to keep in mind when using buffers: + +* Buffers should be opt-in and slave drivers will always have to support + byte-based transactions as the ultimate fallback because this is how the + majority of HW works. + +* For backends simulating hardware registers, buffers are not helpful because + on writes an action should be immediately triggered. For reads, the data in + the buffer might get stale. + +* A master can send STOP at any time. For partially transferred buffers, this + means additional code to handle this exception. Such code tends to be + error-prone. + diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol new file mode 100644 index 000000000..6012b12b3 --- /dev/null +++ b/Documentation/i2c/smbus-protocol @@ -0,0 +1,273 @@ +SMBus Protocol Summary +====================== + +The following is a summary of the SMBus protocol. It applies to +all revisions of the protocol (1.0, 1.1, and 2.0). +Certain protocol features which are not supported by +this package are briefly described at the end of this document. + +Some adapters understand only the SMBus (System Management Bus) protocol, +which is a subset from the I2C protocol. Fortunately, many devices use +only the same subset, which makes it possible to put them on an SMBus. + +If you write a driver for some I2C device, please try to use the SMBus +commands if at all possible (if the device uses only that subset of the +I2C protocol). This makes it possible to use the device driver on both +SMBus adapters and I2C adapters (the SMBus command set is automatically +translated to I2C on I2C adapters, but plain I2C commands can not be +handled at all on most pure SMBus adapters). + +Below is a list of SMBus protocol operations, and the functions executing +them. Note that the names used in the SMBus protocol specifications usually +don't match these function names. For some of the operations which pass a +single data byte, the functions using SMBus protocol operation names execute +a different protocol operation entirely. + +Each transaction type corresponds to a functionality flag. Before calling a +transaction function, a device driver should always check (just once) for +the corresponding functionality flag to ensure that the underlying I2C +adapter supports the transaction in question. See +<file:Documentation/i2c/functionality> for the details. + + +Key to symbols +============== + +S (1 bit) : Start bit +P (1 bit) : Stop bit +Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0. +A, NA (1 bit) : Accept and reverse accept bit. +Addr (7 bits): I2C 7 bit address. Note that this can be expanded as usual to + get a 10 bit I2C address. +Comm (8 bits): Command byte, a data byte which often selects a register on + the device. +Data (8 bits): A plain data byte. Sometimes, I write DataLow, DataHigh + for 16 bit data. +Count (8 bits): A data byte containing the length of a block operation. + +[..]: Data sent by I2C device, as opposed to data sent by the host adapter. + + +SMBus Quick Command +=================== + +This sends a single bit to the device, at the place of the Rd/Wr bit. + +A Addr Rd/Wr [A] P + +Functionality flag: I2C_FUNC_SMBUS_QUICK + + +SMBus Receive Byte: i2c_smbus_read_byte() +========================================== + +This reads a single byte from a device, without specifying a device +register. Some devices are so simple that this interface is enough; for +others, it is a shorthand if you want to read the same register as in +the previous SMBus command. + +S Addr Rd [A] [Data] NA P + +Functionality flag: I2C_FUNC_SMBUS_READ_BYTE + + +SMBus Send Byte: i2c_smbus_write_byte() +======================================== + +This operation is the reverse of Receive Byte: it sends a single byte +to a device. See Receive Byte for more information. + +S Addr Wr [A] Data [A] P + +Functionality flag: I2C_FUNC_SMBUS_WRITE_BYTE + + +SMBus Read Byte: i2c_smbus_read_byte_data() +============================================ + +This reads a single byte from a device, from a designated register. +The register is specified through the Comm byte. + +S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P + +Functionality flag: I2C_FUNC_SMBUS_READ_BYTE_DATA + + +SMBus Read Word: i2c_smbus_read_word_data() +============================================ + +This operation is very like Read Byte; again, data is read from a +device, from a designated register that is specified through the Comm +byte. But this time, the data is a complete word (16 bits). + +S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P + +Functionality flag: I2C_FUNC_SMBUS_READ_WORD_DATA + +Note the convenience function i2c_smbus_read_word_swapped is +available for reads where the two data bytes are the other way +around (not SMBus compliant, but very popular.) + + +SMBus Write Byte: i2c_smbus_write_byte_data() +============================================== + +This writes a single byte to a device, to a designated register. The +register is specified through the Comm byte. This is the opposite of +the Read Byte operation. + +S Addr Wr [A] Comm [A] Data [A] P + +Functionality flag: I2C_FUNC_SMBUS_WRITE_BYTE_DATA + + +SMBus Write Word: i2c_smbus_write_word_data() +============================================== + +This is the opposite of the Read Word operation. 16 bits +of data is written to a device, to the designated register that is +specified through the Comm byte. + +S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P + +Functionality flag: I2C_FUNC_SMBUS_WRITE_WORD_DATA + +Note the convenience function i2c_smbus_write_word_swapped is +available for writes where the two data bytes are the other way +around (not SMBus compliant, but very popular.) + + +SMBus Process Call: +=================== + +This command selects a device register (through the Comm byte), sends +16 bits of data to it, and reads 16 bits of data in return. + +S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] + S Addr Rd [A] [DataLow] A [DataHigh] NA P + +Functionality flag: I2C_FUNC_SMBUS_PROC_CALL + + +SMBus Block Read: i2c_smbus_read_block_data() +============================================== + +This command reads a block of up to 32 bytes from a device, from a +designated register that is specified through the Comm byte. The amount +of data is specified by the device in the Count byte. + +S Addr Wr [A] Comm [A] + S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P + +Functionality flag: I2C_FUNC_SMBUS_READ_BLOCK_DATA + + +SMBus Block Write: i2c_smbus_write_block_data() +================================================ + +The opposite of the Block Read command, this writes up to 32 bytes to +a device, to a designated register that is specified through the +Comm byte. The amount of data is specified in the Count byte. + +S Addr Wr [A] Comm [A] Count [A] Data [A] Data [A] ... [A] Data [A] P + +Functionality flag: I2C_FUNC_SMBUS_WRITE_BLOCK_DATA + + +SMBus Block Write - Block Read Process Call +=========================================== + +SMBus Block Write - Block Read Process Call was introduced in +Revision 2.0 of the specification. + +This command selects a device register (through the Comm byte), sends +1 to 31 bytes of data to it, and reads 1 to 31 bytes of data in return. + +S Addr Wr [A] Comm [A] Count [A] Data [A] ... + S Addr Rd [A] [Count] A [Data] ... A P + +Functionality flag: I2C_FUNC_SMBUS_BLOCK_PROC_CALL + + +SMBus Host Notify +================= + +This command is sent from a SMBus device acting as a master to the +SMBus host acting as a slave. +It is the same form as Write Word, with the command code replaced by the +alerting device's address. + +[S] [HostAddr] [Wr] A [DevAddr] A [DataLow] A [DataHigh] A [P] + + +Packet Error Checking (PEC) +=========================== + +Packet Error Checking was introduced in Revision 1.1 of the specification. + +PEC adds a CRC-8 error-checking byte to transfers using it, immediately +before the terminating STOP. + + +Address Resolution Protocol (ARP) +================================= + +The Address Resolution Protocol was introduced in Revision 2.0 of +the specification. It is a higher-layer protocol which uses the +messages above. + +ARP adds device enumeration and dynamic address assignment to +the protocol. All ARP communications use slave address 0x61 and +require PEC checksums. + + +SMBus Alert +=========== + +SMBus Alert was introduced in Revision 1.0 of the specification. + +The SMBus alert protocol allows several SMBus slave devices to share a +single interrupt pin on the SMBus master, while still allowing the master +to know which slave triggered the interrupt. + +This is implemented the following way in the Linux kernel: +* I2C bus drivers which support SMBus alert should call + i2c_setup_smbus_alert() to setup SMBus alert support. +* I2C drivers for devices which can trigger SMBus alerts should implement + the optional alert() callback. + + +I2C Block Transactions +====================== + +The following I2C block transactions are supported by the +SMBus layer and are described here for completeness. +They are *NOT* defined by the SMBus specification. + +I2C block transactions do not limit the number of bytes transferred +but the SMBus layer places a limit of 32 bytes. + + +I2C Block Read: i2c_smbus_read_i2c_block_data() +================================================ + +This command reads a block of bytes from a device, from a +designated register that is specified through the Comm byte. + +S Addr Wr [A] Comm [A] + S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P + +Functionality flag: I2C_FUNC_SMBUS_READ_I2C_BLOCK + + +I2C Block Write: i2c_smbus_write_i2c_block_data() +================================================== + +The opposite of the Block Read command, this writes bytes to +a device, to a designated register that is specified through the +Comm byte. Note that command lengths of 0, 2, or more bytes are +supported as they are indistinguishable from data. + +S Addr Wr [A] Comm [A] Data [A] Data [A] ... [A] Data [A] P + +Functionality flag: I2C_FUNC_SMBUS_WRITE_I2C_BLOCK diff --git a/Documentation/i2c/summary b/Documentation/i2c/summary new file mode 100644 index 000000000..809541ab3 --- /dev/null +++ b/Documentation/i2c/summary @@ -0,0 +1,43 @@ +I2C and SMBus +============= + +I2C (pronounce: I squared C) is a protocol developed by Philips. It is a +slow two-wire protocol (variable speed, up to 400 kHz), with a high speed +extension (3.4 MHz). It provides an inexpensive bus for connecting many +types of devices with infrequent or low bandwidth communications needs. +I2C is widely used with embedded systems. Some systems use variants that +don't meet branding requirements, and so are not advertised as being I2C. + +SMBus (System Management Bus) is based on the I2C protocol, and is mostly +a subset of I2C protocols and signaling. Many I2C devices will work on an +SMBus, but some SMBus protocols add semantics beyond what is required to +achieve I2C branding. Modern PC mainboards rely on SMBus. The most common +devices connected through SMBus are RAM modules configured using I2C EEPROMs, +and hardware monitoring chips. + +Because the SMBus is mostly a subset of the generalized I2C bus, we can +use its protocols on many I2C systems. However, there are systems that don't +meet both SMBus and I2C electrical constraints; and others which can't +implement all the common SMBus protocol semantics or messages. + + +Terminology +=========== + +When we talk about I2C, we use the following terms: + Bus -> Algorithm + Adapter + Device -> Driver + Client + +An Algorithm driver contains general code that can be used for a whole class +of I2C adapters. Each specific adapter driver either depends on one algorithm +driver, or includes its own implementation. + +A Driver driver (yes, this sounds ridiculous, sorry) contains the general +code to access some type of device. Each detected device gets its own +data in the Client structure. Usually, Driver and Client are more closely +integrated than Algorithm and Adapter. + +For a given configuration, you will need a driver for your I2C bus, and +drivers for your I2C devices (usually one driver for each device). diff --git a/Documentation/i2c/ten-bit-addresses b/Documentation/i2c/ten-bit-addresses new file mode 100644 index 000000000..cdfe13901 --- /dev/null +++ b/Documentation/i2c/ten-bit-addresses @@ -0,0 +1,24 @@ +The I2C protocol knows about two kinds of device addresses: normal 7 bit +addresses, and an extended set of 10 bit addresses. The sets of addresses +do not intersect: the 7 bit address 0x10 is not the same as the 10 bit +address 0x10 (though a single device could respond to both of them). + +I2C messages to and from 10-bit address devices have a different format. +See the I2C specification for the details. + +The current 10 bit address support is minimal. It should work, however +you can expect some problems along the way: +* Not all bus drivers support 10-bit addresses. Some don't because the + hardware doesn't support them (SMBus doesn't require 10-bit address + support for example), some don't because nobody bothered adding the + code (or it's there but not working properly.) Software implementation + (i2c-algo-bit) is known to work. +* Some optional features do not support 10-bit addresses. This is the + case of automatic detection and instantiation of devices by their, + drivers, for example. +* Many user-space packages (for example i2c-tools) lack support for + 10-bit addresses. + +Note that 10-bit address devices are still pretty rare, so the limitations +listed above could stay for a long time, maybe even forever if nobody +needs them to be fixed. diff --git a/Documentation/i2c/upgrading-clients b/Documentation/i2c/upgrading-clients new file mode 100644 index 000000000..ccba3ffd6 --- /dev/null +++ b/Documentation/i2c/upgrading-clients @@ -0,0 +1,279 @@ +Upgrading I2C Drivers to the new 2.6 Driver Model +================================================= + +Ben Dooks <ben-linux@fluff.org> + +Introduction +------------ + +This guide outlines how to alter existing Linux 2.6 client drivers from +the old to the new new binding methods. + + +Example old-style driver +------------------------ + + +struct example_state { + struct i2c_client client; + .... +}; + +static struct i2c_driver example_driver; + +static unsigned short ignore[] = { I2C_CLIENT_END }; +static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END }; + +I2C_CLIENT_INSMOD; + +static int example_attach(struct i2c_adapter *adap, int addr, int kind) +{ + struct example_state *state; + struct device *dev = &adap->dev; /* to use for dev_ reports */ + int ret; + + state = kzalloc(sizeof(struct example_state), GFP_KERNEL); + if (state == NULL) { + dev_err(dev, "failed to create our state\n"); + return -ENOMEM; + } + + example->client.addr = addr; + example->client.flags = 0; + example->client.adapter = adap; + + i2c_set_clientdata(&state->i2c_client, state); + strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE); + + ret = i2c_attach_client(&state->i2c_client); + if (ret < 0) { + dev_err(dev, "failed to attach client\n"); + kfree(state); + return ret; + } + + dev = &state->i2c_client.dev; + + /* rest of the initialisation goes here. */ + + dev_info(dev, "example client created\n"); + + return 0; +} + +static int example_detach(struct i2c_client *client) +{ + struct example_state *state = i2c_get_clientdata(client); + + i2c_detach_client(client); + kfree(state); + return 0; +} + +static int example_attach_adapter(struct i2c_adapter *adap) +{ + return i2c_probe(adap, &addr_data, example_attach); +} + +static struct i2c_driver example_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "example", + .pm = &example_pm_ops, + }, + .attach_adapter = example_attach_adapter, + .detach_client = example_detach, +}; + + +Updating the client +------------------- + +The new style binding model will check against a list of supported +devices and their associated address supplied by the code registering +the busses. This means that the driver .attach_adapter and +.detach_client methods can be removed, along with the addr_data, +as follows: + +- static struct i2c_driver example_driver; + +- static unsigned short ignore[] = { I2C_CLIENT_END }; +- static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END }; + +- I2C_CLIENT_INSMOD; + +- static int example_attach_adapter(struct i2c_adapter *adap) +- { +- return i2c_probe(adap, &addr_data, example_attach); +- } + + static struct i2c_driver example_driver = { +- .attach_adapter = example_attach_adapter, +- .detach_client = example_detach, + } + +Add the probe and remove methods to the i2c_driver, as so: + + static struct i2c_driver example_driver = { ++ .probe = example_probe, ++ .remove = example_remove, + } + +Change the example_attach method to accept the new parameters +which include the i2c_client that it will be working with: + +- static int example_attach(struct i2c_adapter *adap, int addr, int kind) ++ static int example_probe(struct i2c_client *client, ++ const struct i2c_device_id *id) + +Change the name of example_attach to example_probe to align it with the +i2c_driver entry names. The rest of the probe routine will now need to be +changed as the i2c_client has already been setup for use. + +The necessary client fields have already been setup before +the probe function is called, so the following client setup +can be removed: + +- example->client.addr = addr; +- example->client.flags = 0; +- example->client.adapter = adap; +- +- strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE); + +The i2c_set_clientdata is now: + +- i2c_set_clientdata(&state->client, state); ++ i2c_set_clientdata(client, state); + +The call to i2c_attach_client is no longer needed, if the probe +routine exits successfully, then the driver will be automatically +attached by the core. Change the probe routine as so: + +- ret = i2c_attach_client(&state->i2c_client); +- if (ret < 0) { +- dev_err(dev, "failed to attach client\n"); +- kfree(state); +- return ret; +- } + + +Remove the storage of 'struct i2c_client' from the 'struct example_state' +as we are provided with the i2c_client in our example_probe. Instead we +store a pointer to it for when it is needed. + +struct example_state { +- struct i2c_client client; ++ struct i2c_client *client; + +the new i2c client as so: + +- struct device *dev = &adap->dev; /* to use for dev_ reports */ ++ struct device *dev = &i2c_client->dev; /* to use for dev_ reports */ + +And remove the change after our client is attached, as the driver no +longer needs to register a new client structure with the core: + +- dev = &state->i2c_client.dev; + +In the probe routine, ensure that the new state has the client stored +in it: + +static int example_probe(struct i2c_client *i2c_client, + const struct i2c_device_id *id) +{ + struct example_state *state; + struct device *dev = &i2c_client->dev; + int ret; + + state = kzalloc(sizeof(struct example_state), GFP_KERNEL); + if (state == NULL) { + dev_err(dev, "failed to create our state\n"); + return -ENOMEM; + } + ++ state->client = i2c_client; + +Update the detach method, by changing the name to _remove and +to delete the i2c_detach_client call. It is possible that you +can also remove the ret variable as it is not needed for any +of the core functions. + +- static int example_detach(struct i2c_client *client) ++ static int example_remove(struct i2c_client *client) +{ + struct example_state *state = i2c_get_clientdata(client); + +- i2c_detach_client(client); + +And finally ensure that we have the correct ID table for the i2c-core +and other utilities: + ++ struct i2c_device_id example_idtable[] = { ++ { "example", 0 }, ++ { } ++}; ++ ++MODULE_DEVICE_TABLE(i2c, example_idtable); + +static struct i2c_driver example_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "example", + }, ++ .id_table = example_ids, + + +Our driver should now look like this: + +struct example_state { + struct i2c_client *client; + .... +}; + +static int example_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct example_state *state; + struct device *dev = &client->dev; + + state = kzalloc(sizeof(struct example_state), GFP_KERNEL); + if (state == NULL) { + dev_err(dev, "failed to create our state\n"); + return -ENOMEM; + } + + state->client = client; + i2c_set_clientdata(client, state); + + /* rest of the initialisation goes here. */ + + dev_info(dev, "example client created\n"); + + return 0; +} + +static int example_remove(struct i2c_client *client) +{ + struct example_state *state = i2c_get_clientdata(client); + + kfree(state); + return 0; +} + +static struct i2c_device_id example_idtable[] = { + { "example", 0 }, + { } +}; + +MODULE_DEVICE_TABLE(i2c, example_idtable); + +static struct i2c_driver example_driver = { + .driver = { + .owner = THIS_MODULE, + .name = "example", + .pm = &example_pm_ops, + }, + .id_table = example_idtable, + .probe = example_probe, + .remove = example_remove, +}; diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients new file mode 100644 index 000000000..a755b141f --- /dev/null +++ b/Documentation/i2c/writing-clients @@ -0,0 +1,403 @@ +This is a small guide for those who want to write kernel drivers for I2C +or SMBus devices, using Linux as the protocol host/master (not slave). + +To set up a driver, you need to do several things. Some are optional, and +some things can be done slightly or completely different. Use this as a +guide, not as a rule book! + + +General remarks +=============== + +Try to keep the kernel namespace as clean as possible. The best way to +do this is to use a unique prefix for all global symbols. This is +especially important for exported symbols, but it is a good idea to do +it for non-exported symbols too. We will use the prefix `foo_' in this +tutorial. + + +The driver structure +==================== + +Usually, you will implement a single driver structure, and instantiate +all clients from it. Remember, a driver structure contains general access +routines, and should be zero-initialized except for fields with data you +provide. A client structure holds device-specific information like the +driver model device node, and its I2C address. + +static struct i2c_device_id foo_idtable[] = { + { "foo", my_id_for_foo }, + { "bar", my_id_for_bar }, + { } +}; + +MODULE_DEVICE_TABLE(i2c, foo_idtable); + +static struct i2c_driver foo_driver = { + .driver = { + .name = "foo", + .pm = &foo_pm_ops, /* optional */ + }, + + .id_table = foo_idtable, + .probe = foo_probe, + .remove = foo_remove, + /* if device autodetection is needed: */ + .class = I2C_CLASS_SOMETHING, + .detect = foo_detect, + .address_list = normal_i2c, + + .shutdown = foo_shutdown, /* optional */ + .command = foo_command, /* optional, deprecated */ +} + +The name field is the driver name, and must not contain spaces. It +should match the module name (if the driver can be compiled as a module), +although you can use MODULE_ALIAS (passing "foo" in this example) to add +another name for the module. If the driver name doesn't match the module +name, the module won't be automatically loaded (hotplug/coldplug). + +All other fields are for call-back functions which will be explained +below. + + +Extra client data +================= + +Each client structure has a special `data' field that can point to any +structure at all. You should use this to keep device-specific data. + + /* store the value */ + void i2c_set_clientdata(struct i2c_client *client, void *data); + + /* retrieve the value */ + void *i2c_get_clientdata(const struct i2c_client *client); + +Note that starting with kernel 2.6.34, you don't have to set the `data' field +to NULL in remove() or if probe() failed anymore. The i2c-core does this +automatically on these occasions. Those are also the only times the core will +touch this field. + + +Accessing the client +==================== + +Let's say we have a valid client structure. At some time, we will need +to gather information from the client, or write new information to the +client. + +I have found it useful to define foo_read and foo_write functions for this. +For some cases, it will be easier to call the i2c functions directly, +but many chips have some kind of register-value idea that can easily +be encapsulated. + +The below functions are simple examples, and should not be copied +literally. + +int foo_read_value(struct i2c_client *client, u8 reg) +{ + if (reg < 0x10) /* byte-sized register */ + return i2c_smbus_read_byte_data(client, reg); + else /* word-sized register */ + return i2c_smbus_read_word_data(client, reg); +} + +int foo_write_value(struct i2c_client *client, u8 reg, u16 value) +{ + if (reg == 0x10) /* Impossible to write - driver error! */ + return -EINVAL; + else if (reg < 0x10) /* byte-sized register */ + return i2c_smbus_write_byte_data(client, reg, value); + else /* word-sized register */ + return i2c_smbus_write_word_data(client, reg, value); +} + + +Probing and attaching +===================== + +The Linux I2C stack was originally written to support access to hardware +monitoring chips on PC motherboards, and thus used to embed some assumptions +that were more appropriate to SMBus (and PCs) than to I2C. One of these +assumptions was that most adapters and devices drivers support the SMBUS_QUICK +protocol to probe device presence. Another was that devices and their drivers +can be sufficiently configured using only such probe primitives. + +As Linux and its I2C stack became more widely used in embedded systems +and complex components such as DVB adapters, those assumptions became more +problematic. Drivers for I2C devices that issue interrupts need more (and +different) configuration information, as do drivers handling chip variants +that can't be distinguished by protocol probing, or which need some board +specific information to operate correctly. + + +Device/Driver Binding +--------------------- + +System infrastructure, typically board-specific initialization code or +boot firmware, reports what I2C devices exist. For example, there may be +a table, in the kernel or from the boot loader, identifying I2C devices +and linking them to board-specific configuration information about IRQs +and other wiring artifacts, chip type, and so on. That could be used to +create i2c_client objects for each I2C device. + +I2C device drivers using this binding model work just like any other +kind of driver in Linux: they provide a probe() method to bind to +those devices, and a remove() method to unbind. + + static int foo_probe(struct i2c_client *client, + const struct i2c_device_id *id); + static int foo_remove(struct i2c_client *client); + +Remember that the i2c_driver does not create those client handles. The +handle may be used during foo_probe(). If foo_probe() reports success +(zero not a negative status code) it may save the handle and use it until +foo_remove() returns. That binding model is used by most Linux drivers. + +The probe function is called when an entry in the id_table name field +matches the device's name. It is passed the entry that was matched so +the driver knows which one in the table matched. + + +Device Creation +--------------- + +If you know for a fact that an I2C device is connected to a given I2C bus, +you can instantiate that device by simply filling an i2c_board_info +structure with the device address and driver name, and calling +i2c_new_device(). This will create the device, then the driver core will +take care of finding the right driver and will call its probe() method. +If a driver supports different device types, you can specify the type you +want using the type field. You can also specify an IRQ and platform data +if needed. + +Sometimes you know that a device is connected to a given I2C bus, but you +don't know the exact address it uses. This happens on TV adapters for +example, where the same driver supports dozens of slightly different +models, and I2C device addresses change from one model to the next. In +that case, you can use the i2c_new_probed_device() variant, which is +similar to i2c_new_device(), except that it takes an additional list of +possible I2C addresses to probe. A device is created for the first +responsive address in the list. If you expect more than one device to be +present in the address range, simply call i2c_new_probed_device() that +many times. + +The call to i2c_new_device() or i2c_new_probed_device() typically happens +in the I2C bus driver. You may want to save the returned i2c_client +reference for later use. + + +Device Detection +---------------- + +Sometimes you do not know in advance which I2C devices are connected to +a given I2C bus. This is for example the case of hardware monitoring +devices on a PC's SMBus. In that case, you may want to let your driver +detect supported devices automatically. This is how the legacy model +was working, and is now available as an extension to the standard +driver model. + +You simply have to define a detect callback which will attempt to +identify supported devices (returning 0 for supported ones and -ENODEV +for unsupported ones), a list of addresses to probe, and a device type +(or class) so that only I2C buses which may have that type of device +connected (and not otherwise enumerated) will be probed. For example, +a driver for a hardware monitoring chip for which auto-detection is +needed would set its class to I2C_CLASS_HWMON, and only I2C adapters +with a class including I2C_CLASS_HWMON would be probed by this driver. +Note that the absence of matching classes does not prevent the use of +a device of that type on the given I2C adapter. All it prevents is +auto-detection; explicit instantiation of devices is still possible. + +Note that this mechanism is purely optional and not suitable for all +devices. You need some reliable way to identify the supported devices +(typically using device-specific, dedicated identification registers), +otherwise misdetections are likely to occur and things can get wrong +quickly. Keep in mind that the I2C protocol doesn't include any +standard way to detect the presence of a chip at a given address, let +alone a standard way to identify devices. Even worse is the lack of +semantics associated to bus transfers, which means that the same +transfer can be seen as a read operation by a chip and as a write +operation by another chip. For these reasons, explicit device +instantiation should always be preferred to auto-detection where +possible. + + +Device Deletion +--------------- + +Each I2C device which has been created using i2c_new_device() or +i2c_new_probed_device() can be unregistered by calling +i2c_unregister_device(). If you don't call it explicitly, it will be +called automatically before the underlying I2C bus itself is removed, as a +device can't survive its parent in the device driver model. + + +Initializing the driver +======================= + +When the kernel is booted, or when your foo driver module is inserted, +you have to do some initializing. Fortunately, just registering the +driver module is usually enough. + +static int __init foo_init(void) +{ + return i2c_add_driver(&foo_driver); +} +module_init(foo_init); + +static void __exit foo_cleanup(void) +{ + i2c_del_driver(&foo_driver); +} +module_exit(foo_cleanup); + +The module_i2c_driver() macro can be used to reduce above code. + +module_i2c_driver(foo_driver); + +Note that some functions are marked by `__init'. These functions can +be removed after kernel booting (or module loading) is completed. +Likewise, functions marked by `__exit' are dropped by the compiler when +the code is built into the kernel, as they would never be called. + + +Driver Information +================== + +/* Substitute your own name and email address */ +MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>" +MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices"); + +/* a few non-GPL license types are also allowed */ +MODULE_LICENSE("GPL"); + + +Power Management +================ + +If your I2C device needs special handling when entering a system low +power state -- like putting a transceiver into a low power mode, or +activating a system wakeup mechanism -- do that by implementing the +appropriate callbacks for the dev_pm_ops of the driver (like suspend +and resume). + +These are standard driver model calls, and they work just like they +would for any other driver stack. The calls can sleep, and can use +I2C messaging to the device being suspended or resumed (since their +parent I2C adapter is active when these calls are issued, and IRQs +are still enabled). + + +System Shutdown +=============== + +If your I2C device needs special handling when the system shuts down +or reboots (including kexec) -- like turning something off -- use a +shutdown() method. + +Again, this is a standard driver model call, working just like it +would for any other driver stack: the calls can sleep, and can use +I2C messaging. + + +Command function +================ + +A generic ioctl-like function call back is supported. You will seldom +need this, and its use is deprecated anyway, so newer design should not +use it. + + +Sending and receiving +===================== + +If you want to communicate with your device, there are several functions +to do this. You can find all of them in <linux/i2c.h>. + +If you can choose between plain I2C communication and SMBus level +communication, please use the latter. All adapters understand SMBus level +commands, but only some of them understand plain I2C! + + +Plain I2C communication +----------------------- + + int i2c_master_send(struct i2c_client *client, const char *buf, + int count); + int i2c_master_recv(struct i2c_client *client, char *buf, int count); + +These routines read and write some bytes from/to a client. The client +contains the i2c address, so you do not have to include it. The second +parameter contains the bytes to read/write, the third the number of bytes +to read/write (must be less than the length of the buffer, also should be +less than 64k since msg.len is u16.) Returned is the actual number of bytes +read/written. + + int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, + int num); + +This sends a series of messages. Each message can be a read or write, +and they can be mixed in any way. The transactions are combined: no +stop bit is sent between transaction. The i2c_msg structure contains +for each message the client address, the number of bytes of the message +and the message data itself. + +You can read the file `i2c-protocol' for more information about the +actual I2C protocol. + + +SMBus communication +------------------- + + s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, + unsigned short flags, char read_write, u8 command, + int size, union i2c_smbus_data *data); + +This is the generic SMBus function. All functions below are implemented +in terms of it. Never use this function directly! + + s32 i2c_smbus_read_byte(struct i2c_client *client); + s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value); + s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command); + s32 i2c_smbus_write_byte_data(struct i2c_client *client, + u8 command, u8 value); + s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command); + s32 i2c_smbus_write_word_data(struct i2c_client *client, + u8 command, u16 value); + s32 i2c_smbus_read_block_data(struct i2c_client *client, + u8 command, u8 *values); + s32 i2c_smbus_write_block_data(struct i2c_client *client, + u8 command, u8 length, const u8 *values); + s32 i2c_smbus_read_i2c_block_data(struct i2c_client *client, + u8 command, u8 length, u8 *values); + s32 i2c_smbus_write_i2c_block_data(struct i2c_client *client, + u8 command, u8 length, + const u8 *values); + +These ones were removed from i2c-core because they had no users, but could +be added back later if needed: + + s32 i2c_smbus_write_quick(struct i2c_client *client, u8 value); + s32 i2c_smbus_process_call(struct i2c_client *client, + u8 command, u16 value); + s32 i2c_smbus_block_process_call(struct i2c_client *client, + u8 command, u8 length, u8 *values); + +All these transactions return a negative errno value on failure. The 'write' +transactions return 0 on success; the 'read' transactions return the read +value, except for block transactions, which return the number of values +read. The block buffers need not be longer than 32 bytes. + +You can read the file `smbus-protocol' for more information about the +actual SMBus protocol. + + +General purpose routines +======================== + +Below all general purpose routines are listed, that were not mentioned +before. + + /* Return the adapter number for a specific adapter */ + int i2c_adapter_id(struct i2c_adapter *adap); |