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 endianess; 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 endianess.  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