Summary of HDIO_ ioctl callsΒΆ
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.
The drive fails the command (EIO).
One or more than one bits are set in out_flags.
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