==============================
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 5.11)
drivers/ata/libata-scsi.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_32BIT get current io_32bit setting
HDIO_GET_IDENTITY get IDE identification info
HDIO_DRIVE_TASKFILE execute raw taskfile
HDIO_DRIVE_TASK execute task and special drive command
HDIO_DRIVE_CMD execute a special drive command
======================= =======================================
ioctls that pass non-pointer values:
======================= =======================================
HDIO_SET_32BIT change io_32bit flags
======================= =======================================
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_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 Called on a partition instead of the whole disk device
- 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_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_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_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 Called on a partition instead of the whole disk device
- EACCES Access denied: requires CAP_SYS_ADMIN
- EINVAL value out of range [0 3]
- EBUSY Controller busy