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+		Summary of HDIO_ ioctl calls.
+		============================
+
+		Edward A. Falk <efalk@google.com>
+
+		November, 2004
+
+This document attempts to describe the ioctl(2) calls supported by
+the HD/IDE layer.  These are by-and-large implemented (as of Linux 2.6)
+in drivers/ide/ide.c and drivers/block/scsi_ioctl.c
+
+ioctl values are listed in <linux/hdreg.h>.  As of this writing, they
+are as follows:
+
+    ioctls that pass argument pointers to user space:
+
+	HDIO_GETGEO		get device geometry
+	HDIO_GET_UNMASKINTR	get current unmask setting
+	HDIO_GET_MULTCOUNT	get current IDE blockmode setting
+	HDIO_GET_QDMA		get use-qdma flag
+	HDIO_SET_XFER		set transfer rate via proc
+	HDIO_OBSOLETE_IDENTITY	OBSOLETE, DO NOT USE
+	HDIO_GET_KEEPSETTINGS	get keep-settings-on-reset flag
+	HDIO_GET_32BIT		get current io_32bit setting
+	HDIO_GET_NOWERR		get ignore-write-error flag
+	HDIO_GET_DMA		get use-dma flag
+	HDIO_GET_NICE		get nice flags
+	HDIO_GET_IDENTITY	get IDE identification info
+	HDIO_GET_WCACHE		get write cache mode on|off
+	HDIO_GET_ACOUSTIC	get acoustic value
+	HDIO_GET_ADDRESS	get sector addressing mode
+	HDIO_GET_BUSSTATE	get the bus state of the hwif
+	HDIO_TRISTATE_HWIF	execute a channel tristate
+	HDIO_DRIVE_RESET	execute a device reset
+	HDIO_DRIVE_TASKFILE	execute raw taskfile
+	HDIO_DRIVE_TASK		execute task and special drive command
+	HDIO_DRIVE_CMD		execute a special drive command
+	HDIO_DRIVE_CMD_AEB	HDIO_DRIVE_TASK
+
+    ioctls that pass non-pointer values:
+
+	HDIO_SET_MULTCOUNT	change IDE blockmode
+	HDIO_SET_UNMASKINTR	permit other irqs during I/O
+	HDIO_SET_KEEPSETTINGS	keep ioctl settings on reset
+	HDIO_SET_32BIT		change io_32bit flags
+	HDIO_SET_NOWERR		change ignore-write-error flag
+	HDIO_SET_DMA		change use-dma flag
+	HDIO_SET_PIO_MODE	reconfig interface to new speed
+	HDIO_SCAN_HWIF		register and (re)scan interface
+	HDIO_SET_NICE		set nice flags
+	HDIO_UNREGISTER_HWIF	unregister interface
+	HDIO_SET_WCACHE		change write cache enable-disable
+	HDIO_SET_ACOUSTIC	change acoustic behavior
+	HDIO_SET_BUSSTATE	set the bus state of the hwif
+	HDIO_SET_QDMA		change use-qdma flag
+	HDIO_SET_ADDRESS	change lba addressing modes
+
+	HDIO_SET_IDE_SCSI	Set scsi emulation mode on/off
+	HDIO_SET_SCSI_IDE	not implemented yet
+
+
+The information that follows was determined from reading kernel source
+code.  It is likely that some corrections will be made over time.
+
+
+
+
+
+
+
+General:
+
+	Unless otherwise specified, all ioctl calls return 0 on success
+	and -1 with errno set to an appropriate value on error.
+
+	Unless otherwise specified, all ioctl calls return -1 and set
+	errno to EFAULT on a failed attempt to copy data to or from user
+	address space.
+
+	Unless otherwise specified, all data structures and constants
+	are defined in <linux/hdreg.h>
+
+
+
+HDIO_GETGEO			get device geometry
+
+	usage:
+
+	  struct hd_geometry geom;
+	  ioctl(fd, HDIO_GETGEO, &geom);
+
+
+	inputs:		none
+
+	outputs:
+
+	  hd_geometry structure containing:
+
+	    heads	number of heads
+	    sectors	number of sectors/track
+	    cylinders	number of cylinders, mod 65536
+	    start	starting sector of this partition.
+
+
+	error returns:
+	  EINVAL	if the device is not a disk drive or floppy drive,
+	  		or if the user passes a null pointer
+
+
+	notes:
+
+	  Not particularly useful with modern disk drives, whose geometry
+	  is a polite fiction anyway.  Modern drives are addressed
+	  purely by sector number nowadays (lba addressing), and the
+	  drive geometry is an abstraction which is actually subject
+	  to change.  Currently (as of Nov 2004), the geometry values
+	  are the "bios" values -- presumably the values the drive had
+	  when Linux first booted.
+
+	  In addition, the cylinders field of the hd_geometry is an
+	  unsigned short, meaning that on most architectures, this
+	  ioctl will not return a meaningful value on drives with more
+	  than 65535 tracks.
+
+	  The start field is unsigned long, meaning that it will not
+	  contain a meaningful value for disks over 219 Gb in size.
+
+
+
+
+HDIO_GET_UNMASKINTR		get current unmask setting
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_UNMASKINTR, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the drive's current unmask setting
+
+
+
+HDIO_SET_UNMASKINTR		permit other irqs during I/O
+
+	usage:
+
+	  unsigned long val;
+	  ioctl(fd, HDIO_SET_UNMASKINTR, val);
+
+	inputs:
+	  New value for unmask flag
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 1]
+	  EBUSY		Controller busy
+
+
+
+
+HDIO_GET_MULTCOUNT		get current IDE blockmode setting
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_MULTCOUNT, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current IDE block mode setting.  This
+	  controls how many sectors the drive will transfer per
+	  interrupt.
+
+
+
+HDIO_SET_MULTCOUNT		change IDE blockmode
+
+	usage:
+
+	  int val;
+	  ioctl(fd, HDIO_SET_MULTCOUNT, val);
+
+	inputs:
+	  New value for IDE block mode setting.  This controls how many
+	  sectors the drive will transfer per interrupt.
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range supported by disk.
+	  EBUSY		Controller busy or blockmode already set.
+	  EIO		Drive did not accept new block mode.
+
+	notes:
+
+	  Source code comments read:
+
+	    This is tightly woven into the driver->do_special cannot
+	    touch.  DON'T do it again until a total personality rewrite
+	    is committed.
+
+	  If blockmode has already been set, this ioctl will fail with
+	  EBUSY
+
+
+
+HDIO_GET_QDMA			get use-qdma flag
+
+	Not implemented, as of 2.6.8.1
+
+
+
+HDIO_SET_XFER			set transfer rate via proc
+
+	Not implemented, as of 2.6.8.1
+
+
+
+HDIO_OBSOLETE_IDENTITY		OBSOLETE, DO NOT USE
+
+	Same as HDIO_GET_IDENTITY (see below), except that it only
+	returns the first 142 bytes of drive identity information.
+
+
+
+HDIO_GET_IDENTITY		get IDE identification info
+
+	usage:
+
+	  unsigned char identity[512];
+	  ioctl(fd, HDIO_GET_IDENTITY, identity);
+
+	inputs:		none
+
+	outputs:
+
+	  ATA drive identity information.  For full description, see
+	  the IDENTIFY DEVICE and IDENTIFY PACKET DEVICE commands in
+	  the ATA specification.
+
+	error returns:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  ENOMSG	IDENTIFY DEVICE information not available
+
+	notes:
+
+	  Returns information that was obtained when the drive was
+	  probed.  Some of this information is subject to change, and
+	  this ioctl does not re-probe the drive to update the
+	  information.
+
+	  This information is also available from /proc/ide/hdX/identify
+
+
+
+HDIO_GET_KEEPSETTINGS		get keep-settings-on-reset flag
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_KEEPSETTINGS, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current "keep settings" flag
+
+	notes:
+
+	  When set, indicates that kernel should restore settings
+	  after a drive reset.
+
+
+
+HDIO_SET_KEEPSETTINGS		keep ioctl settings on reset
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_SET_KEEPSETTINGS, val);
+
+	inputs:
+	  New value for keep_settings flag
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 1]
+	  EBUSY		Controller busy
+
+
+
+HDIO_GET_32BIT			get current io_32bit setting
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_32BIT, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current io_32bit setting
+
+	notes:
+
+	  0=16-bit, 1=32-bit, 2,3 = 32bit+sync
+
+
+
+HDIO_GET_NOWERR			get ignore-write-error flag
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_NOWERR, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current ignore-write-error flag
+
+
+
+HDIO_GET_DMA			get use-dma flag
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_DMA, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current use-dma flag
+
+
+
+HDIO_GET_NICE			get nice flags
+
+	usage:
+
+	  long nice;
+	  ioctl(fd, HDIO_GET_NICE, &nice);
+
+	inputs:		none
+
+	outputs:
+
+	  The drive's "nice" values.
+
+	notes:
+
+	  Per-drive flags which determine when the system will give more
+	  bandwidth to other devices sharing the same IDE bus.
+	  See <linux/hdreg.h>, near symbol IDE_NICE_DSC_OVERLAP.
+
+
+
+
+HDIO_SET_NICE			set nice flags
+
+	usage:
+
+	  unsigned long nice;
+	  ...
+	  ioctl(fd, HDIO_SET_NICE, nice);
+
+	inputs:
+	  bitmask of nice flags.
+
+	outputs:	none
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EPERM		Flags other than DSC_OVERLAP and NICE_1 set.
+	  EPERM		DSC_OVERLAP specified but not supported by drive
+
+	notes:
+
+	  This ioctl sets the DSC_OVERLAP and NICE_1 flags from values
+	  provided by the user.
+
+	  Nice flags are listed in <linux/hdreg.h>, starting with
+	  IDE_NICE_DSC_OVERLAP.  These values represent shifts.
+
+
+
+
+
+HDIO_GET_WCACHE			get write cache mode on|off
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_WCACHE, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current write cache mode
+
+
+
+HDIO_GET_ACOUSTIC		get acoustic value
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_ACOUSTIC, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current acoustic settings
+
+	notes:
+
+	  See HDIO_SET_ACOUSTIC
+
+
+
+HDIO_GET_ADDRESS
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_GET_ADDRESS, &val);
+
+	inputs:		none
+
+	outputs:
+	  The value of the current addressing mode:
+	    0 = 28-bit
+	    1 = 48-bit
+	    2 = 48-bit doing 28-bit
+	    3 = 64-bit
+
+
+
+HDIO_GET_BUSSTATE		get the bus state of the hwif
+
+	usage:
+
+	  long state;
+	  ioctl(fd, HDIO_SCAN_HWIF, &state);
+
+	inputs:		none
+
+	outputs:
+	  Current power state of the IDE bus.  One of BUSSTATE_OFF,
+	  BUSSTATE_ON, or BUSSTATE_TRISTATE
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+
+
+
+
+HDIO_SET_BUSSTATE		set the bus state of the hwif
+
+	usage:
+
+	  int state;
+	  ...
+	  ioctl(fd, HDIO_SCAN_HWIF, state);
+
+	inputs:
+	  Desired IDE power state.  One of BUSSTATE_OFF, BUSSTATE_ON,
+	  or BUSSTATE_TRISTATE
+
+	outputs:	none
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_RAWIO
+	  EOPNOTSUPP	Hardware interface does not support bus power control
+
+
+
+
+HDIO_TRISTATE_HWIF		execute a channel tristate
+
+	Not implemented, as of 2.6.8.1.  See HDIO_SET_BUSSTATE
+
+
+
+HDIO_DRIVE_RESET		execute a device reset
+
+	usage:
+
+	  int args[3]
+	  ...
+	  ioctl(fd, HDIO_DRIVE_RESET, args);
+
+	inputs:		none
+
+	outputs:	none
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  ENXIO		No such device:	phy dead or ctl_addr == 0
+	  EIO		I/O error:	reset timed out or hardware error
+
+	notes:
+
+	  Execute a reset on the device as soon as the current IO
+	  operation has completed.
+
+	  Executes an ATAPI soft reset if applicable, otherwise
+	  executes an ATA soft reset on the controller.
+
+
+
+HDIO_DRIVE_TASKFILE		execute raw taskfile
+
+	Note:  If you don't have a copy of the ANSI ATA specification
+	handy, you should probably ignore this ioctl.
+
+	Execute an ATA disk command directly by writing the "taskfile"
+	registers of the drive.  Requires ADMIN and RAWIO access
+	privileges.
+
+	usage:
+
+	  struct {
+	    ide_task_request_t req_task;
+	    u8 outbuf[OUTPUT_SIZE];
+	    u8 inbuf[INPUT_SIZE];
+	  } task;
+	  memset(&task.req_task, 0, sizeof(task.req_task));
+	  task.req_task.out_size = sizeof(task.outbuf);
+	  task.req_task.in_size = sizeof(task.inbuf);
+	  ...
+	  ioctl(fd, HDIO_DRIVE_TASKFILE, &task);
+	  ...
+
+	inputs:
+
+	  (See below for details on memory area passed to ioctl.)
+
+	  io_ports[8]	values to be written to taskfile registers
+	  hob_ports[8]	high-order bytes, for extended commands.
+	  out_flags	flags indicating which registers are valid
+	  in_flags	flags indicating which registers should be returned
+	  data_phase	see below
+	  req_cmd	command type to be executed
+	  out_size	size of output buffer
+	  outbuf	buffer of data to be transmitted to disk
+	  inbuf		buffer of data to be received from disk (see [1])
+
+	outputs:
+
+	  io_ports[]	values returned in the taskfile registers
+	  hob_ports[]	high-order bytes, for extended commands.
+	  out_flags	flags indicating which registers are valid (see [2])
+	  in_flags	flags indicating which registers should be returned
+	  outbuf	buffer of data to be transmitted to disk (see [1])
+	  inbuf		buffer of data to be received from disk
+
+	error returns:
+	  EACCES	CAP_SYS_ADMIN or CAP_SYS_RAWIO privilege not set.
+	  ENOMSG	Device is not a disk drive.
+	  ENOMEM	Unable to allocate memory for task
+	  EFAULT	req_cmd == TASKFILE_IN_OUT (not implemented as of 2.6.8)
+	  EPERM		req_cmd == TASKFILE_MULTI_OUT and drive
+	  		multi-count not yet set.
+	  EIO		Drive failed the command.
+
+	notes:
+
+	  [1] READ THE FOLLOWING NOTES *CAREFULLY*.  THIS IOCTL IS
+	  FULL OF GOTCHAS.  Extreme caution should be used with using
+	  this ioctl.  A mistake can easily corrupt data or hang the
+	  system.
+
+	  [2] Both the input and output buffers are copied from the
+	  user and written back to the user, even when not used.
+
+	  [3] If one or more bits are set in out_flags and in_flags is
+	  zero, the following values are used for in_flags.all and
+	  written back into in_flags on completion.
+
+	   * IDE_TASKFILE_STD_IN_FLAGS | (IDE_HOB_STD_IN_FLAGS << 8)
+	     if LBA48 addressing is enabled for the drive
+	   * IDE_TASKFILE_STD_IN_FLAGS
+	     if CHS/LBA28
+
+	  The association between in_flags.all and each enable
+	  bitfield flips depending on endianness; fortunately, TASKFILE
+	  only uses inflags.b.data bit and ignores all other bits.
+	  The end result is that, on any endian machines, it has no
+	  effect other than modifying in_flags on completion.
+
+	  [4] The default value of SELECT is (0xa0|DEV_bit|LBA_bit)
+	  except for four drives per port chipsets.  For four drives
+	  per port chipsets, it's (0xa0|DEV_bit|LBA_bit) for the first
+	  pair and (0x80|DEV_bit|LBA_bit) for the second pair.
+
+	  [5] The argument to the ioctl is a pointer to a region of
+	  memory containing a ide_task_request_t structure, followed
+	  by an optional buffer of data to be transmitted to the
+	  drive, followed by an optional buffer to receive data from
+	  the drive.
+
+	  Command is passed to the disk drive via the ide_task_request_t
+	  structure, which contains these fields:
+
+	    io_ports[8]		values for the taskfile registers
+	    hob_ports[8]	high-order bytes, for extended commands
+	    out_flags		flags indicating which entries in the
+	    			io_ports[] and hob_ports[] arrays
+				contain valid values.  Type ide_reg_valid_t.
+	    in_flags		flags indicating which entries in the
+	    			io_ports[] and hob_ports[] arrays
+				are expected to contain valid values
+				on return.
+	    data_phase		See below
+	    req_cmd		Command type, see below
+	    out_size		output (user->drive) buffer size, bytes
+	    in_size		input (drive->user) buffer size, bytes
+
+	  When out_flags is zero, the following registers are loaded.
+
+	    HOB_FEATURE		If the drive supports LBA48
+	    HOB_NSECTOR		If the drive supports LBA48
+	    HOB_SECTOR		If the drive supports LBA48
+	    HOB_LCYL		If the drive supports LBA48
+	    HOB_HCYL		If the drive supports LBA48
+	    FEATURE
+	    NSECTOR
+	    SECTOR
+	    LCYL
+	    HCYL
+	    SELECT		First, masked with 0xE0 if LBA48, 0xEF
+				otherwise; then, or'ed with the default
+				value of SELECT.
+
+	  If any bit in out_flags is set, the following registers are loaded.
+
+	    HOB_DATA		If out_flags.b.data is set.  HOB_DATA will
+				travel on DD8-DD15 on little endian machines
+				and on DD0-DD7 on big endian machines.
+	    DATA		If out_flags.b.data is set.  DATA will
+				travel on DD0-DD7 on little endian machines
+				and on DD8-DD15 on big endian machines.
+	    HOB_NSECTOR		If out_flags.b.nsector_hob is set
+	    HOB_SECTOR		If out_flags.b.sector_hob is set
+	    HOB_LCYL		If out_flags.b.lcyl_hob is set
+	    HOB_HCYL		If out_flags.b.hcyl_hob is set
+	    FEATURE		If out_flags.b.feature is set
+	    NSECTOR		If out_flags.b.nsector is set
+	    SECTOR		If out_flags.b.sector is set
+	    LCYL		If out_flags.b.lcyl is set
+	    HCYL		If out_flags.b.hcyl is set
+	    SELECT		Or'ed with the default value of SELECT and
+				loaded regardless of out_flags.b.select.
+
+	  Taskfile registers are read back from the drive into
+	  {io|hob}_ports[] after the command completes iff one of the
+	  following conditions is met; otherwise, the original values
+	  will be written back, unchanged.
+
+	    1. The drive fails the command (EIO).
+	    2. One or more than one bits are set in out_flags.
+	    3. The requested data_phase is TASKFILE_NO_DATA.
+
+	    HOB_DATA		If in_flags.b.data is set.  It will contain
+				DD8-DD15 on little endian machines and
+				DD0-DD7 on big endian machines.
+	    DATA		If in_flags.b.data is set.  It will contain
+				DD0-DD7 on little endian machines and
+				DD8-DD15 on big endian machines.
+	    HOB_FEATURE		If the drive supports LBA48
+	    HOB_NSECTOR		If the drive supports LBA48
+	    HOB_SECTOR		If the drive supports LBA48
+	    HOB_LCYL		If the drive supports LBA48
+	    HOB_HCYL		If the drive supports LBA48
+	    NSECTOR
+	    SECTOR
+	    LCYL
+	    HCYL
+
+	  The data_phase field describes the data transfer to be
+	  performed.  Value is one of:
+
+	    TASKFILE_IN
+	    TASKFILE_MULTI_IN
+	    TASKFILE_OUT
+	    TASKFILE_MULTI_OUT
+	    TASKFILE_IN_OUT
+	    TASKFILE_IN_DMA
+	    TASKFILE_IN_DMAQ		== IN_DMA (queueing not supported)
+	    TASKFILE_OUT_DMA
+	    TASKFILE_OUT_DMAQ		== OUT_DMA (queueing not supported)
+	    TASKFILE_P_IN		unimplemented
+	    TASKFILE_P_IN_DMA		unimplemented
+	    TASKFILE_P_IN_DMAQ		unimplemented
+	    TASKFILE_P_OUT		unimplemented
+	    TASKFILE_P_OUT_DMA		unimplemented
+	    TASKFILE_P_OUT_DMAQ		unimplemented
+
+	  The req_cmd field classifies the command type.  It may be
+	  one of:
+
+	    IDE_DRIVE_TASK_NO_DATA
+	    IDE_DRIVE_TASK_SET_XFER	unimplemented
+	    IDE_DRIVE_TASK_IN
+	    IDE_DRIVE_TASK_OUT		unimplemented
+	    IDE_DRIVE_TASK_RAW_WRITE
+
+	  [6] Do not access {in|out}_flags->all except for resetting
+	  all the bits.  Always access individual bit fields.  ->all
+	  value will flip depending on endianness.  For the same
+	  reason, do not use IDE_{TASKFILE|HOB}_STD_{OUT|IN}_FLAGS
+	  constants defined in hdreg.h.
+
+
+
+HDIO_DRIVE_CMD			execute a special drive command
+
+	Note:  If you don't have a copy of the ANSI ATA specification
+	handy, you should probably ignore this ioctl.
+
+	usage:
+
+	  u8 args[4+XFER_SIZE];
+	  ...
+	  ioctl(fd, HDIO_DRIVE_CMD, args);
+
+	inputs:
+
+	  Commands other than WIN_SMART
+	    args[0]	COMMAND
+	    args[1]	NSECTOR
+	    args[2]	FEATURE
+	    args[3]	NSECTOR
+
+	  WIN_SMART
+	    args[0]	COMMAND
+	    args[1]	SECTOR
+	    args[2]	FEATURE
+	    args[3]	NSECTOR
+
+	outputs:
+
+	  args[] buffer is filled with register values followed by any
+	  data returned by the disk.
+	    args[0]	status
+	    args[1]	error
+	    args[2]	NSECTOR
+	    args[3]	undefined
+	    args[4+]	NSECTOR * 512 bytes of data returned by the command.
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_RAWIO
+	  ENOMEM	Unable to allocate memory for task
+	  EIO		Drive reports error
+
+	notes:
+
+	  [1] For commands other than WIN_SMART, args[1] should equal
+	  args[3].  SECTOR, LCYL and HCYL are undefined.  For
+	  WIN_SMART, 0x4f and 0xc2 are loaded into LCYL and HCYL
+	  respectively.  In both cases SELECT will contain the default
+	  value for the drive.  Please refer to HDIO_DRIVE_TASKFILE
+	  notes for the default value of SELECT.
+
+	  [2] If NSECTOR value is greater than zero and the drive sets
+	  DRQ when interrupting for the command, NSECTOR * 512 bytes
+	  are read from the device into the area following NSECTOR.
+	  In the above example, the area would be
+	  args[4..4+XFER_SIZE].  16bit PIO is used regardless of
+	  HDIO_SET_32BIT setting.
+
+	  [3] If COMMAND == WIN_SETFEATURES && FEATURE == SETFEATURES_XFER
+	  && NSECTOR >= XFER_SW_DMA_0 && the drive supports any DMA
+	  mode, IDE driver will try to tune the transfer mode of the
+	  drive accordingly.
+
+
+
+HDIO_DRIVE_TASK			execute task and special drive command
+
+	Note:  If you don't have a copy of the ANSI ATA specification
+	handy, you should probably ignore this ioctl.
+
+	usage:
+
+	  u8 args[7];
+	  ...
+	  ioctl(fd, HDIO_DRIVE_TASK, args);
+
+	inputs:
+
+	  Taskfile register values:
+	    args[0]	COMMAND
+	    args[1]	FEATURE
+	    args[2]	NSECTOR
+	    args[3]	SECTOR
+	    args[4]	LCYL
+	    args[5]	HCYL
+	    args[6]	SELECT
+
+	outputs:
+
+	  Taskfile register values:
+	    args[0]	status
+	    args[1]	error
+	    args[2]	NSECTOR
+	    args[3]	SECTOR
+	    args[4]	LCYL
+	    args[5]	HCYL
+	    args[6]	SELECT
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_RAWIO
+	  ENOMEM	Unable to allocate memory for task
+	  ENOMSG	Device is not a disk drive.
+	  EIO		Drive failed the command.
+
+	notes:
+
+	  [1] DEV bit (0x10) of SELECT register is ignored and the
+	  appropriate value for the drive is used.  All other bits
+	  are used unaltered.
+
+
+
+HDIO_DRIVE_CMD_AEB		HDIO_DRIVE_TASK
+
+	Not implemented, as of 2.6.8.1
+
+
+
+HDIO_SET_32BIT			change io_32bit flags
+
+	usage:
+
+	  int val;
+	  ioctl(fd, HDIO_SET_32BIT, val);
+
+	inputs:
+	  New value for io_32bit flag
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 3]
+	  EBUSY		Controller busy
+
+
+
+
+HDIO_SET_NOWERR			change ignore-write-error flag
+
+	usage:
+
+	  int val;
+	  ioctl(fd, HDIO_SET_NOWERR, val);
+
+	inputs:
+	  New value for ignore-write-error flag.  Used for ignoring
+	  WRERR_STAT
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 1]
+	  EBUSY		Controller busy
+
+
+
+HDIO_SET_DMA			change use-dma flag
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_SET_DMA, val);
+
+	inputs:
+	  New value for use-dma flag
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 1]
+	  EBUSY		Controller busy
+
+
+
+HDIO_SET_PIO_MODE		reconfig interface to new speed
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_SET_PIO_MODE, val);
+
+	inputs:
+	  New interface speed.
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 255]
+	  EBUSY		Controller busy
+
+
+
+HDIO_SCAN_HWIF			register and (re)scan interface
+
+	usage:
+
+	  int args[3]
+	  ...
+	  ioctl(fd, HDIO_SCAN_HWIF, args);
+
+	inputs:
+	  args[0]	io address to probe
+	  args[1]	control address to probe
+	  args[2]	irq number
+
+	outputs:	none
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_RAWIO
+	  EIO		Probe failed.
+
+	notes:
+
+	  This ioctl initializes the addresses and irq for a disk
+	  controller, probes for drives, and creates /proc/ide
+	  interfaces as appropriate.
+
+
+
+HDIO_UNREGISTER_HWIF		unregister interface
+
+	usage:
+
+	  int index;
+	  ioctl(fd, HDIO_UNREGISTER_HWIF, index);
+
+	inputs:
+	  index		index of hardware interface to unregister
+
+	outputs:	none
+
+	error returns:
+	  EACCES	Access denied:  requires CAP_SYS_RAWIO
+
+	notes:
+
+	  This ioctl removes a hardware interface from the kernel.
+
+	  Currently (2.6.8) this ioctl silently fails if any drive on
+	  the interface is busy.
+
+
+
+HDIO_SET_WCACHE			change write cache enable-disable
+
+	usage:
+
+	  int val;
+	  ioctl(fd, HDIO_SET_WCACHE, val);
+
+	inputs:
+	  New value for write cache enable
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 1]
+	  EBUSY		Controller busy
+
+
+
+HDIO_SET_ACOUSTIC		change acoustic behavior
+
+	usage:
+
+	  int val;
+	  ioctl(fd, HDIO_SET_ACOUSTIC, val);
+
+	inputs:
+	  New value for drive acoustic settings
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 254]
+	  EBUSY		Controller busy
+
+
+
+HDIO_SET_QDMA			change use-qdma flag
+
+	Not implemented, as of 2.6.8.1
+
+
+
+HDIO_SET_ADDRESS		change lba addressing modes
+
+	usage:
+
+	  int val;
+	  ioctl(fd, HDIO_SET_ADDRESS, val);
+
+	inputs:
+	  New value for addressing mode
+	    0 = 28-bit
+	    1 = 48-bit
+	    2 = 48-bit doing 28-bit
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 2]
+	  EBUSY		Controller busy
+	  EIO		Drive does not support lba48 mode.
+
+
+HDIO_SET_IDE_SCSI
+
+	usage:
+
+	  long val;
+	  ioctl(fd, HDIO_SET_IDE_SCSI, val);
+
+	inputs:
+	  New value for scsi emulation mode (?)
+
+	outputs:	none
+
+	error return:
+	  EINVAL	(bdev != bdev->bd_contains) (not sure what this means)
+	  EACCES	Access denied:  requires CAP_SYS_ADMIN
+	  EINVAL	value out of range [0 1]
+	  EBUSY		Controller busy
+
+
+
+HDIO_SET_SCSI_IDE
+
+	Not implemented, as of 2.6.8.1
+
+