Ioctl Numbers

19 October 1999

Michael Elizabeth Chastain <mec@shout.net>

If you are adding new ioctl’s to the kernel, you should use the _IO macros defined in <linux/ioctl.h>:

_IO

an

ioctl with no parameters

_IOW

an

ioctl with write parameters (copy_from_user)

_IOR

an

ioctl with read parameters (copy_to_user)

_IOWR

an

ioctl with both write and read parameters.

‘Write’ and ‘read’ are from the user’s point of view, just like the system calls ‘write’ and ‘read’. For example, a SET_FOO ioctl would be _IOW, although the kernel would actually read data from user space; a GET_FOO ioctl would be _IOR, although the kernel would actually write data to user space.

The first argument to _IO, _IOW, _IOR, or _IOWR is an identifying letter or number from the table below. Because of the large number of drivers, many drivers share a partial letter with other drivers.

If you are writing a driver for a new device and need a letter, pick an unused block with enough room for expansion: 32 to 256 ioctl commands. You can register the block by patching this file and submitting the patch to Linus Torvalds. Or you can e-mail me at <mec@shout.net> and I’ll register one for you.

The second argument to _IO, _IOW, _IOR, or _IOWR is a sequence number to distinguish ioctls from each other. The third argument to _IOW, _IOR, or _IOWR is the type of the data going into the kernel or coming out of the kernel (e.g. ‘int’ or ‘struct foo’). NOTE! Do NOT use sizeof(arg) as the third argument as this results in your ioctl thinking it passes an argument of type size_t.

Some devices use their major number as the identifier; this is OK, as long as it is unique. Some devices are irregular and don’t follow any convention at all.

Following this convention is good because:

  1. Keeping the ioctl’s globally unique helps error checking: if a program calls an ioctl on the wrong device, it will get an error rather than some unexpected behaviour.

  2. The ‘strace’ build procedure automatically finds ioctl numbers defined with _IO, _IOW, _IOR, or _IOWR.

  3. ‘strace’ can decode numbers back into useful names when the numbers are unique.

  4. People looking for ioctls can grep for them more easily when this convention is used to define the ioctl numbers.

  5. When following the convention, the driver code can use generic code to copy the parameters between user and kernel space.

This table lists ioctls visible from user land for Linux/x86. It contains most drivers up to 2.6.31, but I know I am missing some. There has been no attempt to list non-X86 architectures or ioctls from drivers/staging/.

Code

Seq# (hex)

Include File

Comments

0x00

00-1F

linux/fs.h

conflict!

0x00

00-1F

scsi/scsi_ioctl.h

conflict!

0x00

00-1F

linux/fb.h

conflict!

0x00

00-1F

linux/wavefront.h

conflict!

0x02

all

linux/fd.h

0x03

all

linux/hdreg.h

0x04

D2-DC

linux/umsdos_fs.h

Dead since 2.6.11, but don’t reuse these.

0x06

all

linux/lp.h

0x09

all

linux/raid/md_u.h

0x10

00-0F

drivers/char/s390/vmcp.h

0x10

10-1F

arch/s390/include/uapi/sclp_ctl.h

0x10

20-2F

arch/s390/include/uapi/asm/hypfs.h

0x12

all

linux/fs.h linux/blkpg.h

0x1b

all

InfiniBand Subsystem <http://infiniband.sourceforge.net/>

0x20

all

drivers/cdrom/cm206.h

0x22

all

scsi/sg.h

‘!’

00-1F

uapi/linux/seccomp.h

‘#’

00-3F

IEEE 1394 Subsystem Block for the entire subsystem

‘$’

00-0F

linux/perf_counter.h, linux/perf_event.h

‘%’

00-0F

include/uapi/linux/stm.h

System Trace Module subsystem <mailto:alexander.shishkin@linux.intel.com>

‘&’

00-07

drivers/firewire/nosy-user.h

‘1’

00-1F

linux/timepps.h

PPS kit from Ulrich Windl <ftp://ftp.de.kernel.org/pub/linux/daemons/ntp/PPS/>

‘2’

01-04

linux/i2o.h

‘3’

00-0F

drivers/s390/char/raw3270.h

conflict!

‘3’

00-1F

linux/suspend_ioctls.h, kernel/power/user.c

conflict!

‘8’

all

SNP8023 advanced NIC card <mailto:mcr@solidum.com>

‘;’

64-7F

linux/vfio.h

‘@’

00-0F

linux/radeonfb.h

conflict!

‘@’

00-0F

drivers/video/aty/aty128fb.c

conflict!

‘A’

00-1F

linux/apm_bios.h

conflict!

‘A’

00-0F

linux/agpgart.h, drivers/char/agp/compat_ioctl.h

conflict!

‘A’

00-7F

sound/asound.h

conflict!

‘B’

00-1F

linux/cciss_ioctl.h

conflict!

‘B’

00-0F

include/linux/pmu.h

conflict!

‘B’

C0-FF

advanced bbus

<mailto:maassen@uni-freiburg.de>

‘C’

all

linux/soundcard.h

conflict!

‘C’

01-2F

linux/capi.h

conflict!

‘C’

F0-FF

drivers/net/wan/cosa.h

conflict!

‘D’

all

arch/s390/include/asm/dasd.h

‘D’

40-5F

drivers/scsi/dpt/dtpi_ioctl.h

‘D’

05

drivers/scsi/pmcraid.h

‘E’

all

linux/input.h

conflict!

‘E’

00-0F

xen/evtchn.h

conflict!

‘F’

all

linux/fb.h

conflict!

‘F’

01-02

drivers/scsi/pmcraid.h

conflict!

‘F’

20

drivers/video/fsl-diu-fb.h

conflict!

‘F’

20

drivers/video/intelfb/intelfb.h

conflict!

‘F’

20

linux/ivtvfb.h

conflict!

‘F’

20

linux/matroxfb.h

conflict!

‘F’

20

drivers/video/aty/atyfb_base.c

conflict!

‘F’

00-0F

video/da8xx-fb.h

conflict!

‘F’

80-8F

linux/arcfb.h

conflict!

‘F’

DD

video/sstfb.h

conflict!

‘G’

00-3F

drivers/misc/sgi-gru/grulib.h

conflict!

‘H’

00-7F

linux/hiddev.h

conflict!

‘H’

00-0F

linux/hidraw.h

conflict!

‘H’

01

linux/mei.h

conflict!

‘H’

02

linux/mei.h

conflict!

‘H’

03

linux/mei.h

conflict!

‘H’

00-0F

sound/asound.h

conflict!

‘H’

20-40

sound/asound_fm.h

conflict!

‘H’

80-8F

sound/sfnt_info.h

conflict!

‘H’

10-8F

sound/emu10k1.h

conflict!

‘H’

10-1F

sound/sb16_csp.h

conflict!

‘H’

10-1F

sound/hda_hwdep.h

conflict!

‘H’

40-4F

sound/hdspm.h

conflict!

‘H’

40-4F

sound/hdsp.h

conflict!

‘H’

90

sound/usb/usx2y/usb_stream.h

‘H’

00-0F

uapi/misc/habanalabs.h

conflict!

‘H’

A0

uapi/linux/usb/cdc-wdm.h

‘H’

C0-F0

net/bluetooth/hci.h

conflict!

‘H’

C0-DF

net/bluetooth/hidp/hidp.h

conflict!

‘H’

C0-DF

net/bluetooth/cmtp/cmtp.h

conflict!

‘H’

C0-DF

net/bluetooth/bnep/bnep.h

conflict!

‘H’

F1

linux/hid-roccat.h

<mailto:erazor_de@users.sourceforge.net>

‘H’

F8-FA

sound/firewire.h

‘I’

all

linux/isdn.h

conflict!

‘I’

00-0F

drivers/isdn/divert/isdn_divert.h

conflict!

‘I’

40-4F

linux/mISDNif.h

conflict!

‘J’

00-1F

drivers/scsi/gdth_ioctl.h

‘K’

all

linux/kd.h

‘L’

00-1F

linux/loop.h

conflict!

‘L’

10-1F

drivers/scsi/mpt3sas/mpt3sas_ctl.h

conflict!

‘L’

20-2F

linux/lightnvm.h

‘L’

E0-FF

linux/ppdd.h

encrypted disk device driver <http://linux01.gwdg.de/~alatham/ppdd.html>

‘M’

all

linux/soundcard.h

conflict!

‘M’

01-16 and

mtd/mtd-abi.h drivers/mtd/mtdchar.c

conflict!

‘M’

01-03

drivers/scsi/megaraid/megaraid_sas.h

‘M’

00-0F

drivers/video/fsl-diu-fb.h

conflict!

‘N’

00-1F

drivers/usb/scanner.h

‘N’

40-7F

drivers/block/nvme.c

‘O’

00-06

mtd/ubi-user.h

UBI

‘P’

all

linux/soundcard.h

conflict!

‘P’

60-6F

sound/sscape_ioctl.h

conflict!

‘P’

00-0F

drivers/usb/class/usblp.c

conflict!

‘P’

01-09

drivers/misc/pci_endpoint_test.c

conflict!

‘Q’

all

linux/soundcard.h

‘R’

00-1F

linux/random.h

conflict!

‘R’

01

linux/rfkill.h

conflict!

‘R’

C0-DF

net/bluetooth/rfcomm.h

‘S’

all

linux/cdrom.h

conflict!

‘S’

80-81

scsi/scsi_ioctl.h

conflict!

‘S’

82-FF

scsi/scsi.h

conflict!

‘S’

00-7F

sound/asequencer.h

conflict!

‘T’

all

linux/soundcard.h

conflict!

‘T’

00-AF

sound/asound.h

conflict!

‘T’

all

arch/x86/include/asm/ioctls.h

conflict!

‘T’

C0-DF

linux/if_tun.h

conflict!

‘U’

all

sound/asound.h

conflict!

‘U’

00-CF

linux/uinput.h

conflict!

‘U’

00-EF

linux/usbdevice_fs.h

‘U’

C0-CF

drivers/bluetooth/hci_uart.h

‘V’

all

linux/vt.h

conflict!

‘V’

all

linux/videodev2.h

conflict!

‘V’

C0

linux/ivtvfb.h

conflict!

‘V’

C0

linux/ivtv.h

conflict!

‘V’

C0

media/davinci/vpfe_capture.h

conflict!

‘V’

C0

media/si4713.h

conflict!

‘W’

00-1F

linux/watchdog.h

conflict!

‘W’

00-1F

linux/wanrouter.h

conflict! (pre 3.9)

‘W’

00-3F

sound/asound.h

conflict!

‘W’

40-5F

drivers/pci/switch/switchtec.c

‘W’

60-61

linux/watch_queue.h

‘X’

all

fs/xfs/xfs_fs.h, fs/xfs/linux-2.6/xfs_ioctl32.h, include/linux/falloc.h, linux/fs.h,

conflict!

‘X’

all

fs/ocfs2/ocfs_fs.h

conflict!

‘X’

01

linux/pktcdvd.h

conflict!

‘Y’

all

linux/cyclades.h

‘Z’

14-15

drivers/message/fusion/mptctl.h

‘[‘

00-3F

linux/usb/tmc.h

USB Test and Measurement Devices <mailto:gregkh@linuxfoundation.org>

‘a’

all

linux/atm*.h, linux/sonet.h

ATM on linux <http://lrcwww.epfl.ch/>

‘a’

00-0F

drivers/crypto/qat/qat_common/adf_cfg_common.h

conflict! qat driver

‘b’

00-FF

conflict! bit3 vme host bridge <mailto:natalia@nikhefk.nikhef.nl>

‘c’

all

linux/cm4000_cs.h

conflict!

‘c’

00-7F

linux/comstats.h

conflict!

‘c’

00-7F

linux/coda.h

conflict!

‘c’

00-1F

linux/chio.h

conflict!

‘c’

80-9F

arch/s390/include/asm/chsc.h

conflict!

‘c’

A0-AF

arch/x86/include/asm/msr.h conflict!

‘d’

00-FF

linux/char/drm/drm.h

conflict!

‘d’

02-40

pcmcia/ds.h

conflict!

‘d’

F0-FF

linux/digi1.h

‘e’

all

linux/digi1.h

conflict!

‘f’

00-1F

linux/ext2_fs.h

conflict!

‘f’

00-1F

linux/ext3_fs.h

conflict!

‘f’

00-0F

fs/jfs/jfs_dinode.h

conflict!

‘f’

00-0F

fs/ext4/ext4.h

conflict!

‘f’

00-0F

linux/fs.h

conflict!

‘f’

00-0F

fs/ocfs2/ocfs2_fs.h

conflict!

‘f’

13-27

linux/fscrypt.h

‘f’

81-8F

linux/fsverity.h

‘g’

00-0F

linux/usb/gadgetfs.h

‘g’

20-2F

linux/usb/g_printer.h

‘h’

00-7F

conflict! Charon filesystem <mailto:zapman@interlan.net>

‘h’

00-1F

linux/hpet.h

conflict!

‘h’

80-8F

fs/hfsplus/ioctl.c

‘i’

00-3F

linux/i2o-dev.h

conflict!

‘i’

0B-1F

linux/ipmi.h

conflict!

‘i’

80-8F

linux/i8k.h

‘j’

00-3F

linux/joystick.h

‘k’

00-0F

linux/spi/spidev.h

conflict!

‘k’

00-05

video/kyro.h

conflict!

‘k’

10-17

linux/hsi/hsi_char.h

HSI character device

‘l’

00-3F

linux/tcfs_fs.h

transparent cryptographic file system <http://web.archive.org/web/%2A/http://mikonos.dia.unisa.it/tcfs>

‘l’

40-7F

linux/udf_fs_i.h

in development: <http://sourceforge.net/projects/linux-udf/>

‘m’

00-09

linux/mmtimer.h

conflict!

‘m’

all

linux/mtio.h

conflict!

‘m’

all

linux/soundcard.h

conflict!

‘m’

all

linux/synclink.h

conflict!

‘m’

00-19

drivers/message/fusion/mptctl.h

conflict!

‘m’

00

drivers/scsi/megaraid/megaraid_ioctl.h

conflict!

‘n’

00-7F

linux/ncp_fs.h and fs/ncpfs/ioctl.c

‘n’

80-8F

uapi/linux/nilfs2_api.h

NILFS2

‘n’

E0-FF

linux/matroxfb.h

matroxfb

‘o’

00-1F

fs/ocfs2/ocfs2_fs.h

OCFS2

‘o’

00-03

mtd/ubi-user.h

conflict! (OCFS2 and UBI overlaps)

‘o’

40-41

mtd/ubi-user.h

UBI

‘o’

01-A1

linux/dvb/*.h

DVB

‘p’

00-0F

linux/phantom.h

conflict! (OpenHaptics needs this)

‘p’

00-1F

linux/rtc.h

conflict!

‘p’

40-7F

linux/nvram.h

‘p’

80-9F

linux/ppdev.h

user-space parport <mailto:tim@cyberelk.net>

‘p’

A1-A5

linux/pps.h

LinuxPPS <mailto:giometti@linux.it>

‘q’

00-1F

linux/serio.h

‘q’

80-FF

linux/telephony.h linux/ixjuser.h

Internet PhoneJACK, Internet LineJACK <http://web.archive.org/web/%2A/http://www.quicknet.net>

‘r’

00-1F

linux/msdos_fs.h and fs/fat/dir.c

‘s’

all

linux/cdk.h

‘t’

00-7F

linux/ppp-ioctl.h

‘t’

80-8F

linux/isdn_ppp.h

‘t’

90-91

linux/toshiba.h

toshiba and toshiba_acpi SMM

‘u’

00-1F

linux/smb_fs.h

gone

‘u’

20-3F

linux/uvcvideo.h

USB video class host driver

‘u’

40-4f

linux/udmabuf.h

userspace dma-buf misc device

‘v’

00-1F

linux/ext2_fs.h

conflict!

‘v’

00-1F

linux/fs.h

conflict!

‘v’

00-0F

linux/sonypi.h

conflict!

‘v’

00-0F

media/v4l2-subdev.h

conflict!

‘v’

20-27

arch/powerpc/include/uapi/asm/vas-api.h

VAS API

‘v’

C0-FF

linux/meye.h

conflict!

‘w’

all

CERN SCI driver

‘y’

00-1F

packet based user level communications <mailto:zapman@interlan.net>

‘z’

00-3F

CAN bus card conflict! <mailto:hdstich@connectu.ulm.circular.de>

‘z’

40-7F

CAN bus card conflict! <mailto:oe@port.de>

‘z’

10-4F

drivers/s390/crypto/zcrypt_api.h

conflict!

‘|’

00-7F

linux/media.h

0x80

00-1F

linux/fb.h

0x89

00-06

arch/x86/include/asm/sockios.h

0x89

0B-DF

linux/sockios.h

0x89

E0-EF

linux/sockios.h

SIOCPROTOPRIVATE range

0x89

E0-EF

linux/dn.h

PROTOPRIVATE range

0x89

F0-FF

linux/sockios.h

SIOCDEVPRIVATE range

0x8B

all

linux/wireless.h

0x8C

00-3F

WiNRADiO driver <http://www.winradio.com.au/>

0x90

00

drivers/cdrom/sbpcd.h

0x92

00-0F

drivers/usb/mon/mon_bin.c

0x93

60-7F

linux/auto_fs.h

0x94

all

fs/btrfs/ioctl.h and linux/fs.h

Btrfs filesystem some lifted to vfs/generic

0x97

00-7F

fs/ceph/ioctl.h

Ceph file system

0x99

00-0F

537-Addinboard driver <mailto:buk@buks.ipn.de>

0xA0

all

linux/sdp/sdp.h

Industrial Device Project <mailto:kenji@bitgate.com>

0xA1

0

linux/vtpm_proxy.h

TPM Emulator Proxy Driver

0xA3

80-8F

Port ACL in development: <mailto:tlewis@mindspring.com>

0xA3

90-9F

linux/dtlk.h

0xA4

00-1F

uapi/linux/tee.h

Generic TEE subsystem

0xAA

00-3F

linux/uapi/linux/userfaultfd.h

0xAB

00-1F

linux/nbd.h

0xAC

00-1F

linux/raw.h

0xAD

00

Netfilter device in development: <mailto:rusty@rustcorp.com.au>

0xAE

all

linux/kvm.h

Kernel-based Virtual Machine <mailto:kvm@vger.kernel.org>

0xAF

00-1F

linux/fsl_hypervisor.h

Freescale hypervisor

0xB0

all

RATIO devices in development: <mailto:vgo@ratio.de>

0xB1

00-1F

PPPoX <mailto:mostrows@styx.uwaterloo.ca>

0xB3

00

linux/mmc/ioctl.h

0xB4

00-0F

linux/gpio.h

<mailto:linux-gpio@vger.kernel.org>

0xB5

00-0F

uapi/linux/rpmsg.h

<mailto:linux-remoteproc@vger.kernel.org>

0xB6

all

linux/fpga-dfl.h

0xB7

all

uapi/linux/remoteproc_cdev.h

<mailto:linux-remoteproc@vger.kernel.org>

0xC0

00-0F

linux/usb/iowarrior.h

0xCA

00-0F

uapi/misc/cxl.h

0xCA

10-2F

uapi/misc/ocxl.h

0xCA

80-BF

uapi/scsi/cxlflash_ioctl.h

0xCB

00-1F

CBM serial IEC bus in development: <mailto:michael.klein@puffin.lb.shuttle.de>

0xCC

00-0F

drivers/misc/ibmvmc.h

pseries VMC driver

0xCD

01

linux/reiserfs_fs.h

0xCF

02

fs/cifs/ioctl.c

0xDB

00-0F

drivers/char/mwave/mwavepub.h

0xDD

00-3F

ZFCP device driver see drivers/s390/scsi/ <mailto:aherrman@de.ibm.com>

0xE5

00-3F

linux/fuse.h

0xEC

00-01

drivers/platform/chrome/cros_ec_dev.h

ChromeOS EC driver

0xF3

00-3F

drivers/usb/misc/sisusbvga/sisusb.h

sisfb (in development) <mailto:thomas@winischhofer.net>

0xF4

00-1F

video/mbxfb.h

mbxfb <mailto:raph@8d.com>

0xF6

all

LTTng Linux Trace Toolkit Next Generation <mailto:mathieu.desnoyers@efficios.com>

0xFD

all

linux/dm-ioctl.h

0xFE

all

linux/isst_if.h