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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

        notes:

          Abort any current command, prevent anything else from being
          queued, execute a reset on the device, and issue BLKRRPART
          ioctl on the block device.

          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