Initial import

14 files changed, 680 insertions, 0 deletions

diff --git a/Documentation/w1/00-INDEX b/Documentation/w1/00-INDEX
new file mode 100644
index 000000000..cb4980274
--- /dev/null
+++ b/Documentation/w1/00-INDEX
@@ -0,0 +1,10 @@
+00-INDEX
+	- This file
+slaves/
+	- Drivers that provide support for specific family codes.
+masters/
+	- Individual chips providing 1-wire busses.
+w1.generic
+	- The 1-wire (w1) bus
+w1.netlink
+	- Userspace communication protocol over connector [1].
diff --git a/Documentation/w1/masters/00-INDEX b/Documentation/w1/masters/00-INDEX
new file mode 100644
index 000000000..8330cf932
--- /dev/null
+++ b/Documentation/w1/masters/00-INDEX
@@ -0,0 +1,12 @@
+00-INDEX
+	- This file
+ds2482
+	- The Maxim/Dallas Semiconductor DS2482 provides 1-wire busses.
+ds2490
+	- The Maxim/Dallas Semiconductor DS2490 builds USB <-> W1 bridges.
+mxc-w1
+	- W1 master controller driver found on Freescale MX2/MX3 SoCs
+omap-hdq
+	- HDQ/1-wire module of TI OMAP 2430/3430.
+w1-gpio
+	- GPIO 1-wire bus master driver.
diff --git a/Documentation/w1/masters/ds2482 b/Documentation/w1/masters/ds2482
new file mode 100644
index 000000000..56f8edace
--- /dev/null
+++ b/Documentation/w1/masters/ds2482
@@ -0,0 +1,31 @@
+Kernel driver ds2482
+====================
+
+Supported chips:
+  * Maxim DS2482-100, Maxim DS2482-800
+    Prefix: 'ds2482'
+    Addresses scanned: None
+    Datasheets:
+        http://datasheets.maxim-ic.com/en/ds/DS2482-100.pdf
+        http://datasheets.maxim-ic.com/en/ds/DS2482-800.pdf
+
+Author: Ben Gardner <bgardner@wabtec.com>
+
+
+Description
+-----------
+
+The Maxim/Dallas Semiconductor DS2482 is a I2C device that provides
+one (DS2482-100) or eight (DS2482-800) 1-wire busses.
+
+
+General Remarks
+---------------
+
+Valid addresses are 0x18, 0x19, 0x1a, and 0x1b.
+However, the device cannot be detected without writing to the i2c bus, so no
+detection is done. You should instantiate the device explicitly.
+
+$ modprobe ds2482
+$ echo ds2482 0x18 > /sys/bus/i2c/devices/i2c-0/new_device
+
diff --git a/Documentation/w1/masters/ds2490 b/Documentation/w1/masters/ds2490
new file mode 100644
index 000000000..3e091151d
--- /dev/null
+++ b/Documentation/w1/masters/ds2490
@@ -0,0 +1,68 @@
+Kernel driver ds2490
+====================
+
+Supported chips:
+  * Maxim DS2490 based
+
+Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
+
+
+Description
+-----------
+
+The Maxim/Dallas Semiconductor DS2490 is a chip
+which allows to build USB <-> W1 bridges.
+
+DS9490(R) is a USB <-> W1 bus master device
+which has 0x81 family ID integrated chip and DS2490
+low-level operational chip.
+
+Notes and limitations.
+- The weak pullup current is a minimum of 0.9mA and maximum of 6.0mA.
+- The 5V strong pullup is supported with a minimum of 5.9mA and a
+  maximum of 30.4 mA.  (From DS2490.pdf)
+- The hardware will detect when devices are attached to the bus on the
+  next bus (reset?) operation, however only a message is printed as
+  the core w1 code doesn't make use of the information.  Connecting
+  one device tends to give multiple new device notifications.
+- The number of USB bus transactions could be reduced if w1_reset_send
+  was added to the API.  The name is just a suggestion.  It would take
+  a write buffer and a read buffer (along with sizes) as arguments.
+  The ds2490 block I/O command supports reset, write buffer, read
+  buffer, and strong pullup all in one command, instead of the current
+  1 reset bus, 2 write the match rom command and slave rom id, 3 block
+  write and read data.  The write buffer needs to have the match rom
+  command and slave rom id prepended to the front of the requested
+  write buffer, both of which are known to the driver.
+- The hardware supports normal, flexible, and overdrive bus
+  communication speeds, but only the normal is supported.
+- The registered w1_bus_master functions don't define error
+  conditions.  If a bus search is in progress and the ds2490 is
+  removed it can produce a good amount of error output before the bus
+  search finishes.
+- The hardware supports detecting some error conditions, such as
+  short, alarming presence on reset, and no presence on reset, but the
+  driver doesn't query those values.
+- The ds2490 specification doesn't cover short bulk in reads in
+  detail, but my observation is if fewer bytes are requested than are
+  available, the bulk read will return an error and the hardware will
+  clear the entire bulk in buffer.  It would be possible to read the
+  maximum buffer size to not run into this error condition, only extra
+  bytes in the buffer is a logic error in the driver.  The code should
+  should match reads and writes as well as data sizes.  Reads and
+  writes are serialized and the status verifies that the chip is idle
+  (and data is available) before the read is executed, so it should
+  not happen.
+- Running x86_64 2.6.24 UHCI under qemu 0.9.0 under x86_64 2.6.22-rc6
+  with a OHCI controller, ds2490 running in the guest would operate
+  normally the first time the module was loaded after qemu attached
+  the ds2490 hardware, but if the module was unloaded, then reloaded
+  most of the time one of the bulk out or in, and usually the bulk in
+  would fail.  qemu sets a 50ms timeout and the bulk in would timeout
+  even when the status shows data available.  A bulk out write would
+  show a successful completion, but the ds2490 status register would
+  show 0 bytes written.  Detaching qemu from the ds2490 hardware and
+  reattaching would clear the problem.  usbmon output in the guest and
+  host did not explain the problem.  My guess is a bug in either qemu
+  or the host OS and more likely the host OS.
+-- 03-06-2008 David Fries <David@Fries.net>
diff --git a/Documentation/w1/masters/mxc-w1 b/Documentation/w1/masters/mxc-w1
new file mode 100644
index 000000000..38be1ad65
--- /dev/null
+++ b/Documentation/w1/masters/mxc-w1
@@ -0,0 +1,12 @@
+Kernel driver mxc_w1
+====================
+
+Supported chips:
+  * Freescale MX27, MX31 and probably other i.MX SoCs
+    Datasheets:
+        http://www.freescale.com/files/32bit/doc/data_sheet/MCIMX31.pdf?fpsp=1
+	http://cache.freescale.com/files/dsp/doc/archive/MCIMX27.pdf?fsrch=1&WT_TYPE=
+	Data%20Sheets&WT_VENDOR=FREESCALE&WT_FILE_FORMAT=pdf&WT_ASSET=Documentation
+
+Author: Originally based on Freescale code, prepared for mainline by
+	Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/Documentation/w1/masters/omap-hdq b/Documentation/w1/masters/omap-hdq
new file mode 100644
index 000000000..884dc284b
--- /dev/null
+++ b/Documentation/w1/masters/omap-hdq
@@ -0,0 +1,46 @@
+Kernel driver for omap HDQ/1-wire module.
+========================================
+
+Supported chips:
+================
+	HDQ/1-wire controller on the TI OMAP 2430/3430 platforms.
+
+A useful link about HDQ basics:
+===============================
+http://focus.ti.com/lit/an/slua408a/slua408a.pdf
+
+Description:
+============
+The HDQ/1-Wire module of TI OMAP2430/3430 platforms implement the hardware
+protocol of the master functions of the Benchmark HDQ and the Dallas
+Semiconductor 1-Wire protocols. These protocols use a single wire for
+communication between the master (HDQ/1-Wire controller) and the slave
+(HDQ/1-Wire external compliant device).
+
+A typical application of the HDQ/1-Wire module is the communication with battery
+monitor (gas gauge) integrated circuits.
+
+The controller supports operation in both HDQ and 1-wire mode. The essential
+difference between the HDQ and 1-wire mode is how the slave device responds to
+initialization pulse.In HDQ mode, the firmware does not require the host to
+create an initialization pulse to the slave.However, the slave can be reset by
+using an initialization pulse (also referred to as a break pulse).The slave
+does not respond with a presence pulse as it does in the 1-Wire protocol.
+
+Remarks:
+========
+The driver (drivers/w1/masters/omap_hdq.c) supports the HDQ mode of the
+controller. In this mode, as we can not read the ID which obeys the W1
+spec(family:id:crc), a module parameter can be passed to the driver which will
+be used to calculate the CRC and pass back an appropriate slave ID to the W1
+core.
+
+By default the master driver and the BQ slave i/f
+driver(drivers/w1/slaves/w1_bq27000.c) sets the ID to 1.
+Please note to load both the modules with a different ID if required, but note
+that the ID used should be same for both master and slave driver loading.
+
+e.g:
+insmod omap_hdq.ko W1_ID=2
+inamod w1_bq27000.ko F_ID=2
+
diff --git a/Documentation/w1/masters/w1-gpio b/Documentation/w1/masters/w1-gpio
new file mode 100644
index 000000000..af5d3b4aa
--- /dev/null
+++ b/Documentation/w1/masters/w1-gpio
@@ -0,0 +1,33 @@
+Kernel driver w1-gpio
+=====================
+
+Author: Ville Syrjala <syrjala@sci.fi>
+
+
+Description
+-----------
+
+GPIO 1-wire bus master driver. The driver uses the GPIO API to control the
+wire and the GPIO pin can be specified using platform data.
+
+
+Example (mach-at91)
+-------------------
+
+#include <linux/w1-gpio.h>
+
+static struct w1_gpio_platform_data foo_w1_gpio_pdata = {
+	.pin		= AT91_PIN_PB20,
+	.is_open_drain	= 1,
+};
+
+static struct platform_device foo_w1_device = {
+	.name			= "w1-gpio",
+	.id			= -1,
+	.dev.platform_data	= &foo_w1_gpio_pdata,
+};
+
+...
+	at91_set_GPIO_periph(foo_w1_gpio_pdata.pin, 1);
+	at91_set_multi_drive(foo_w1_gpio_pdata.pin, 1);
+	platform_device_register(&foo_w1_device);
diff --git a/Documentation/w1/slaves/00-INDEX b/Documentation/w1/slaves/00-INDEX
new file mode 100644
index 000000000..6e18c70c3
--- /dev/null
+++ b/Documentation/w1/slaves/00-INDEX
@@ -0,0 +1,8 @@
+00-INDEX
+	- This file
+w1_therm
+	- The Maxim/Dallas Semiconductor ds18*20 temperature sensor.
+w1_ds2423
+	- The Maxim/Dallas Semiconductor ds2423 counter device.
+w1_ds28e04
+	- The Maxim/Dallas Semiconductor ds28e04 eeprom.
diff --git a/Documentation/w1/slaves/w1_ds2406 b/Documentation/w1/slaves/w1_ds2406
new file mode 100644
index 000000000..8137fe6f6
--- /dev/null
+++ b/Documentation/w1/slaves/w1_ds2406
@@ -0,0 +1,25 @@
+w1_ds2406 kernel driver
+=======================
+
+Supported chips:
+  * Maxim DS2406 (and other family 0x12) addressable switches
+
+Author: Scott Alfter <scott@alfter.us>
+
+Description
+-----------
+
+The w1_ds2406 driver allows connected devices to be switched on and off. 
+These chips also provide 128 bytes of OTP EPROM, but reading/writing it is
+not supported.  In TSOC-6 form, the DS2406 provides two switch outputs and
+can be provided with power on a dedicated input.  In TO-92 form, it provides
+one output and uses parasitic power only.
+
+The driver provides two sysfs files.  state is readable; it gives the
+current state of each switch, with PIO A in bit 0 and PIO B in bit 1.  The
+driver ORs this state with 0x30, so shell scripts get an ASCII 0/1/2/3 to
+work with.  output is writable; bits 0 and 1 control PIO A and B,
+respectively.  Bits 2-7 are ignored, so it's safe to write ASCII data.
+
+CRCs are checked on read and write.  Failed checks cause an I/O error to be
+returned.  On a failed write, the switch status is not changed.
diff --git a/Documentation/w1/slaves/w1_ds2423 b/Documentation/w1/slaves/w1_ds2423
new file mode 100644
index 000000000..3f98b505a
--- /dev/null
+++ b/Documentation/w1/slaves/w1_ds2423
@@ -0,0 +1,47 @@
+Kernel driver w1_ds2423
+=======================
+
+Supported chips:
+  * Maxim DS2423 based counter devices.
+
+supported family codes:
+	W1_THERM_DS2423	0x1D
+
+Author: Mika Laitio <lamikr@pilppa.org>
+
+Description
+-----------
+
+Support is provided through the sysfs w1_slave file. Each opening and
+read sequence of w1_slave file initiates the read of counters and ram
+available in DS2423 pages 12 - 15.
+
+Result of each page is provided as an ASCII output where each counter
+value and associated ram buffer is outpputed to own line.
+
+Each lines will contain the values of 42 bytes read from the counter and
+memory page along the crc=YES or NO for indicating whether the read operation
+was successful and CRC matched.
+If the operation was successful, there is also in the end of each line
+a counter value expressed as an integer after c=
+
+Meaning of 42 bytes represented is following:
+ - 1 byte from ram page
+ - 4 bytes for the counter value
+ - 4 zero bytes
+ - 2 bytes for crc16 which was calculated from the data read since the previous crc bytes
+ - 31 remaining bytes from the ram page
+ - crc=YES/NO indicating whether read was ok and crc matched
+ - c=<int> current counter value
+
+example from the successful read:
+00 02 00 00 00 00 00 00 00 6d 38 00 ff ff 00 00 fe ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff crc=YES c=2
+00 02 00 00 00 00 00 00 00 e0 1f 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff crc=YES c=2
+00 29 c6 5d 18 00 00 00 00 04 37 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff crc=YES c=408798761
+00 05 00 00 00 00 00 00 00 8d 39 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff crc=YES c=5
+
+example from the read with crc errors:
+00 02 00 00 00 00 00 00 00 6d 38 00 ff ff 00 00 fe ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff crc=YES c=2
+00 02 00 00 22 00 00 00 00 e0 1f 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff crc=NO
+00 e1 61 5d 19 00 00 00 00 df 0b 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff 00 00 ff ff crc=NO
+00 05 00 00 20 00 00 00 00 8d 39 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff crc=NO
diff --git a/Documentation/w1/slaves/w1_ds28e04 b/Documentation/w1/slaves/w1_ds28e04
new file mode 100644
index 000000000..7819b65cf
--- /dev/null
+++ b/Documentation/w1/slaves/w1_ds28e04
@@ -0,0 +1,36 @@
+Kernel driver w1_ds28e04
+========================
+
+Supported chips:
+  * Maxim DS28E04-100 4096-Bit Addressable 1-Wire EEPROM with PIO
+
+supported family codes:
+	W1_FAMILY_DS28E04	0x1C
+
+Author: Markus Franke, <franke.m@sebakmt.com> <franm@hrz.tu-chemnitz.de>
+
+Description
+-----------
+
+Support is provided through the sysfs files "eeprom" and "pio". CRC checking
+during memory accesses can optionally be enabled/disabled via the device
+attribute "crccheck". The strong pull-up can optionally be enabled/disabled
+via the module parameter "w1_strong_pullup".
+
+Memory Access
+
+	A read operation on the "eeprom" file reads the given amount of bytes
+	from the EEPROM of the DS28E04.
+
+	A write operation on the "eeprom" file writes the given byte sequence
+	to the EEPROM of the DS28E04. If CRC checking mode is enabled only
+	fully aligned blocks of 32 bytes with valid CRC16 values (in bytes 30
+	and 31) are allowed to be written.
+
+PIO Access
+
+	The 2 PIOs of the DS28E04-100 are accessible via the "pio" sysfs file.
+
+	The current status of the PIO's is returned as an 8 bit value. Bit 0/1
+	represent the state of PIO_0/PIO_1. Bits 2..7 do not care. The PIO's are
+	driven low-active, i.e. the driver delivers/expects low-active values.
diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm
new file mode 100644
index 000000000..cc62a95e4
--- /dev/null
+++ b/Documentation/w1/slaves/w1_therm
@@ -0,0 +1,50 @@
+Kernel driver w1_therm
+====================
+
+Supported chips:
+  * Maxim ds18*20 based temperature sensors.
+  * Maxim ds1825 based temperature sensors.
+
+Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
+
+
+Description
+-----------
+
+w1_therm provides basic temperature conversion for ds18*20 devices.
+supported family codes:
+W1_THERM_DS18S20	0x10
+W1_THERM_DS1822		0x22
+W1_THERM_DS18B20	0x28
+W1_THERM_DS1825		0x3B
+
+Support is provided through the sysfs w1_slave file.  Each open and
+read sequence will initiate a temperature conversion then provide two
+lines of ASCII output.  The first line contains the nine hex bytes
+read along with a calculated crc value and YES or NO if it matched.
+If the crc matched the returned values are retained.  The second line
+displays the retained values along with a temperature in millidegrees
+Centigrade after t=.
+
+Parasite powered devices are limited to one slave performing a
+temperature conversion at a time.  If none of the devices are parasite
+powered it would be possible to convert all the devices at the same
+time and then go back to read individual sensors.  That isn't
+currently supported.  The driver also doesn't support reduced
+precision (which would also reduce the conversion time).
+
+The module parameter strong_pullup can be set to 0 to disable the
+strong pullup, 1 to enable autodetection or 2 to force strong pullup.
+In case of autodetection, the driver will use the "READ POWER SUPPLY"
+command to check if there are pariste powered devices on the bus.
+If so, it will activate the master's strong pullup.
+In case the detection of parasite devices using this command fails
+(seems to be the case with some DS18S20) the strong pullup can
+be force-enabled.
+If the strong pullup is enabled, the master's strong pullup will be
+driven when the conversion is taking place, provided the master driver
+does support the strong pullup (or it falls back to a pullup
+resistor).  The DS18b20 temperature sensor specification lists a
+maximum current draw of 1.5mA and that a 5k pullup resistor is not
+sufficient.  The strong pullup is designed to provide the additional
+current required.
diff --git a/Documentation/w1/w1.generic b/Documentation/w1/w1.generic
new file mode 100644
index 000000000..b2033c64c
--- /dev/null
+++ b/Documentation/w1/w1.generic
@@ -0,0 +1,113 @@
+The 1-wire (w1) subsystem
+------------------------------------------------------------------
+The 1-wire bus is a simple master-slave bus that communicates via a single
+signal wire (plus ground, so two wires).
+
+Devices communicate on the bus by pulling the signal to ground via an open
+drain output and by sampling the logic level of the signal line.
+
+The w1 subsystem provides the framework for managing w1 masters and
+communication with slaves.
+
+All w1 slave devices must be connected to a w1 bus master device.
+
+Example w1 master devices:
+    DS9490 usb device
+    W1-over-GPIO
+    DS2482 (i2c to w1 bridge)
+    Emulated devices, such as a RS232 converter, parallel port adapter, etc
+
+
+What does the w1 subsystem do?
+------------------------------------------------------------------
+When a w1 master driver registers with the w1 subsystem, the following occurs:
+
+ - sysfs entries for that w1 master are created
+ - the w1 bus is periodically searched for new slave devices
+
+When a device is found on the bus, w1 core tries to load the driver for its family
+and check if it is loaded. If so, the family driver is attached to the slave.
+If there is no driver for the family, default one is assigned, which allows to perform
+almost any kind of operations. Each logical operation is a transaction
+in nature, which can contain several (two or one) low-level operations.
+Let's see how one can read EEPROM context:
+1. one must write control buffer, i.e. buffer containing command byte
+and two byte address. At this step bus is reset and appropriate device
+is selected using either W1_SKIP_ROM or W1_MATCH_ROM command.
+Then provided control buffer is being written to the wire.
+2. reading. This will issue reading eeprom response.
+
+It is possible that between 1. and 2. w1 master thread will reset bus for searching
+and slave device will be even removed, but in this case 0xff will
+be read, since no device was selected.
+
+
+W1 device families
+------------------------------------------------------------------
+Slave devices are handled by a driver written for a family of w1 devices.
+
+A family driver populates a struct w1_family_ops (see w1_family.h) and
+registers with the w1 subsystem.
+
+Current family drivers:
+w1_therm - (ds18?20 thermal sensor family driver)
+    provides temperature reading function which is bound to ->rbin() method
+    of the above w1_family_ops structure.
+
+w1_smem - driver for simple 64bit memory cell provides ID reading method.
+
+You can call above methods by reading appropriate sysfs files.
+
+
+What does a w1 master driver need to implement?
+------------------------------------------------------------------
+
+The driver for w1 bus master must provide at minimum two functions.
+
+Emulated devices must provide the ability to set the output signal level
+(write_bit) and sample the signal level (read_bit).
+
+Devices that support the 1-wire natively must provide the ability to write and
+sample a bit (touch_bit) and reset the bus (reset_bus).
+
+Most hardware provides higher-level functions that offload w1 handling.
+See struct w1_bus_master definition in w1.h for details.
+
+
+w1 master sysfs interface
+------------------------------------------------------------------
+<xx-xxxxxxxxxxxxx> - a directory for a found device. The format is family-serial
+bus                - (standard) symlink to the w1 bus
+driver             - (standard) symlink to the w1 driver
+w1_master_add      - Manually register a slave device
+w1_master_attempts - the number of times a search was attempted
+w1_master_max_slave_count
+                   - maximum number of slaves to search for at a time
+w1_master_name     - the name of the device (w1_bus_masterX)
+w1_master_pullup   - 5V strong pullup 0 enabled, 1 disabled
+w1_master_remove   - Manually remove a slave device
+w1_master_search   - the number of searches left to do, -1=continual (default)
+w1_master_slave_count
+                   - the number of slaves found
+w1_master_slaves   - the names of the slaves, one per line
+w1_master_timeout  - the delay in seconds between searches
+
+If you have a w1 bus that never changes (you don't add or remove devices),
+you can set the module parameter search_count to a small positive number
+for an initially small number of bus searches.  Alternatively it could be
+set to zero, then manually add the slave device serial numbers by
+w1_master_add device file.  The w1_master_add and w1_master_remove files
+generally only make sense when searching is disabled, as a search will
+redetect manually removed devices that are present and timeout manually
+added devices that aren't on the bus.
+
+
+w1 slave sysfs interface
+------------------------------------------------------------------
+bus                - (standard) symlink to the w1 bus
+driver             - (standard) symlink to the w1 driver
+name               - the device name, usually the same as the directory name
+w1_slave           - (optional) a binary file whose meaning depends on the
+                     family driver
+rw		   - (optional) created for slave devices which do not have
+		     appropriate family driver. Allows to read/write binary data.
diff --git a/Documentation/w1/w1.netlink b/Documentation/w1/w1.netlink
new file mode 100644
index 000000000..ef2727192
--- /dev/null
+++ b/Documentation/w1/w1.netlink
@@ -0,0 +1,189 @@
+Userspace communication protocol over connector [1].
+
+
+Message types.
+=============
+
+There are three types of messages between w1 core and userspace:
+1. Events. They are generated each time a new master or slave device
+	is found either due to automatic or requested search.
+2. Userspace commands.
+3. Replies to userspace commands.
+
+
+Protocol.
+========
+
+[struct cn_msg] - connector header.
+	Its length field is equal to size of the attached data
+[struct w1_netlink_msg] - w1 netlink header.
+	__u8 type 	- message type.
+			W1_LIST_MASTERS
+				list current bus masters
+			W1_SLAVE_ADD/W1_SLAVE_REMOVE
+				slave add/remove events
+			W1_MASTER_ADD/W1_MASTER_REMOVE
+				master add/remove events
+			W1_MASTER_CMD
+				userspace command for bus master
+				device (search/alarm search)
+			W1_SLAVE_CMD
+				userspace command for slave device
+				(read/write/touch)
+	__u8 status	- error indication from kernel
+	__u16 len	- size of data attached to this header data
+	union {
+		__u8 id[8];			 - slave unique device id
+		struct w1_mst {
+			__u32		id;	 - master's id
+			__u32		res;	 - reserved
+		} mst;
+	} id;
+
+[struct w1_netlink_cmd] - command for given master or slave device.
+	__u8 cmd	- command opcode.
+			W1_CMD_READ 	- read command
+			W1_CMD_WRITE	- write command
+			W1_CMD_SEARCH	- search command
+			W1_CMD_ALARM_SEARCH - alarm search command
+			W1_CMD_TOUCH	- touch command
+				(write and sample data back to userspace)
+			W1_CMD_RESET	- send bus reset
+			W1_CMD_SLAVE_ADD	- add slave to kernel list
+			W1_CMD_SLAVE_REMOVE	- remove slave from kernel list
+			W1_CMD_LIST_SLAVES	- get slaves list from kernel
+	__u8 res	- reserved
+	__u16 len	- length of data for this command
+		For read command data must be allocated like for write command
+	__u8 data[0]	- data for this command
+
+
+Each connector message can include one or more w1_netlink_msg with
+zero or more attached w1_netlink_cmd messages.
+
+For event messages there are no w1_netlink_cmd embedded structures,
+only connector header and w1_netlink_msg strucutre with "len" field
+being zero and filled type (one of event types) and id:
+either 8 bytes of slave unique id in host order,
+or master's id, which is assigned to bus master device
+when it is added to w1 core.
+
+Currently replies to userspace commands are only generated for read
+command request. One reply is generated exactly for one w1_netlink_cmd
+read request. Replies are not combined when sent - i.e. typical reply
+messages looks like the following:
+
+[cn_msg][w1_netlink_msg][w1_netlink_cmd]
+cn_msg.len = sizeof(struct w1_netlink_msg) +
+	     sizeof(struct w1_netlink_cmd) +
+	     cmd->len;
+w1_netlink_msg.len = sizeof(struct w1_netlink_cmd) + cmd->len;
+w1_netlink_cmd.len = cmd->len;
+
+Replies to W1_LIST_MASTERS should send a message back to the userspace
+which will contain list of all registered master ids in the following
+format:
+
+	cn_msg (CN_W1_IDX.CN_W1_VAL as id, len is equal to sizeof(struct
+	w1_netlink_msg) plus number of masters multiplied by 4)
+	w1_netlink_msg (type: W1_LIST_MASTERS, len is equal to
+		number of masters multiplied by 4 (u32 size))
+	id0 ... idN
+
+	Each message is at most 4k in size, so if number of master devices
+	exceeds this, it will be split into several messages.
+
+W1 search and alarm search commands.
+request:
+[cn_msg]
+  [w1_netlink_msg type = W1_MASTER_CMD
+  	id is equal to the bus master id to use for searching]
+  [w1_netlink_cmd cmd = W1_CMD_SEARCH or W1_CMD_ALARM_SEARCH]
+
+reply:
+  [cn_msg, ack = 1 and increasing, 0 means the last message,
+  	seq is equal to the request seq]
+  [w1_netlink_msg type = W1_MASTER_CMD]
+  [w1_netlink_cmd cmd = W1_CMD_SEARCH or W1_CMD_ALARM_SEARCH
+	len is equal to number of IDs multiplied by 8]
+  [64bit-id0 ... 64bit-idN]
+Length in each header corresponds to the size of the data behind it, so
+w1_netlink_cmd->len = N * 8; where N is number of IDs in this message.
+	Can be zero.
+w1_netlink_msg->len = sizeof(struct w1_netlink_cmd) + N * 8;
+cn_msg->len = sizeof(struct w1_netlink_msg) +
+	      sizeof(struct w1_netlink_cmd) +
+	      N*8;
+
+W1 reset command.
+[cn_msg]
+  [w1_netlink_msg type = W1_MASTER_CMD
+  	id is equal to the bus master id to use for searching]
+  [w1_netlink_cmd cmd = W1_CMD_RESET]
+
+
+Command status replies.
+======================
+
+Each command (either root, master or slave with or without w1_netlink_cmd
+structure) will be 'acked' by the w1 core. Format of the reply is the same
+as request message except that length parameters do not account for data
+requested by the user, i.e. read/write/touch IO requests will not contain
+data, so w1_netlink_cmd.len will be 0, w1_netlink_msg.len will be size
+of the w1_netlink_cmd structure and cn_msg.len will be equal to the sum
+of the sizeof(struct w1_netlink_msg) and sizeof(struct w1_netlink_cmd).
+If reply is generated for master or root command (which do not have
+w1_netlink_cmd attached), reply will contain only cn_msg and w1_netlink_msg
+structures.
+
+w1_netlink_msg.status field will carry positive error value
+(EINVAL for example) or zero in case of success.
+
+All other fields in every structure will mirror the same parameters in the
+request message (except lengths as described above).
+
+Status reply is generated for every w1_netlink_cmd embedded in the
+w1_netlink_msg, if there are no w1_netlink_cmd structures,
+reply will be generated for the w1_netlink_msg.
+
+All w1_netlink_cmd command structures are handled in every w1_netlink_msg,
+even if there were errors, only length mismatch interrupts message processing.
+
+
+Operation steps in w1 core when new command is received.
+=======================================================
+
+When new message (w1_netlink_msg) is received w1 core detects if it is
+master or slave request, according to w1_netlink_msg.type field.
+Then master or slave device is searched for.
+When found, master device (requested or those one on where slave device
+is found) is locked. If slave command is requested, then reset/select
+procedure is started to select given device.
+
+Then all requested in w1_netlink_msg operations are performed one by one.
+If command requires reply (like read command) it is sent on command completion.
+
+When all commands (w1_netlink_cmd) are processed master device is unlocked
+and next w1_netlink_msg header processing started.
+
+
+Connector [1] specific documentation.
+====================================
+
+Each connector message includes two u32 fields as "address".
+w1 uses CN_W1_IDX and CN_W1_VAL defined in include/linux/connector.h header.
+Each message also includes sequence and acknowledge numbers.
+Sequence number for event messages is appropriate bus master sequence number
+increased with each event message sent "through" this master.
+Sequence number for userspace requests is set by userspace application.
+Sequence number for reply is the same as was in request, and
+acknowledge number is set to seq+1.
+
+
+Additional documantion, source code examples.
+============================================
+
+1. Documentation/connector
+2. http://www.ioremap.net/archive/w1
+This archive includes userspace application w1d.c which uses
+read/write/search commands for all master/slave devices found on the bus.