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Ioctl Numbers

Documentation/userspace-api/ioctl/ioctl-number.rst

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============= Ioctl Numbers

19 October 1999

Michael Elizabeth Chastain [email protected]

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

====== ===========================
macro  parameters
====== ===========================
_IO    none
_IOW   write (read from userspace)
_IOR   read (write to userspace)
_IOWR  write and read
====== ===========================

'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 the macros 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 should suffice. You can register the block by patching this file and submitting the patch through :doc:usual patch submission process </process/submitting-patches>.

The second argument is a sequence number to distinguish ioctls from each other. The third argument (not applicable to _IO) 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 the macros.

(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 userland, excluding ones from drivers/staging/.

==== ===== ========================================================= ================================================================ Code Seq# Include File Comments (hex) ==== ===== ========================================================= ================================================================ 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 0x07 9F-D0 linux/vmw_vmci_defs.h, uapi/linux/vm_sockets.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 BLK* ioctls linux/blkpg.h linux/blkzoned.h linux/blk-crypto.h 0x15 all linux/fs.h FS_IOC_* ioctls 0x1b all InfiniBand Subsystem http://infiniband.sourceforge.net/ 0x20 all drivers/cdrom/cm206.h 0x22 all scsi/sg.h 0x3E 00-0F linux/counter.h mailto:[email protected] '!' 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:[email protected] '&' 00-07 drivers/firewire/nosy-user.h '' 00-1F uapi/linux/user_events.h User Events Subsystem mailto:[email protected] '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, conflict! kernel/power/user.c '8' all SNP8023 advanced NIC card mailto:[email protected] ';' 64-7F linux/vfio.h ';' 80-FF linux/iommufd.h '=' 00-3f uapi/linux/ptp_clock.h mailto:[email protected] '@' 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, conflict! drivers/char/agp/compat_ioctl.h '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:[email protected] 'B' 00-0F xen/xenbus_dev.h conflict! '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 Dead since 2022 '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 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! 'G' 00-0F xen/gntalloc.h, xen/gntdev.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:[email protected] '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! 'K' all linux/kd.h 'L' 00-1F linux/loop.h conflict! 'L' 10-1F drivers/scsi/mpt3sas/mpt3sas_ctl.h conflict! '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 mtd/mtd-abi.h conflict! and drivers/mtd/mtdchar.c '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 'N' 80-8F uapi/linux/ntsync.h NT synchronization primitives mailto:[email protected] '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! 'P' 00-0F xen/privcmd.h conflict! 'P' 00-05 linux/tps6594_pfsm.h conflict! 'Q' all linux/soundcard.h 'R' 00-1F linux/random.h conflict! 'R' 01 linux/rfkill.h conflict! 'R' 20-2F linux/trace_mmap.h 'R' C0-DF net/bluetooth/rfcomm.h 'R' E0 uapi/linux/fsl_mc.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/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, conflict! fs/xfs/linux-2.6/xfs_ioctl32.h, include/linux/falloc.h, linux/fs.h, 'X' all fs/ocfs2/ocfs_fs.h conflict! 'Z' 14-15 drivers/message/fusion/mptctl.h '[' 00-3F linux/usb/tmc.h USB Test and Measurement Devices mailto:[email protected] '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:[email protected] 'b' 00-0F linux/dma-buf.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:[email protected] '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 'i' 90-9F linux/iio/*.h IIO '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: https://github.com/pali/udftools '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:[email protected] 'p' A1-A5 linux/pps.h LinuxPPS 'p' B1-B3 linux/pps_gen.h LinuxPPS mailto:[email protected] 'q' 00-1F linux/serio.h 'q' 80-FF linux/telephony.h Internet PhoneJACK, Internet LineJACK linux/ixjuser.h 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' 00-2F linux/ublk_cmd.h conflict! '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:[email protected] 'z' 00-3F CAN bus card conflict! mailto:[email protected] 'z' 40-7F CAN bus card conflict! mailto:[email protected] 'z' 10-4F drivers/s390/crypto/zcrypt_api.h conflict! '|' 00-7F linux/media.h '|' 80-9F samples/ Any sample and example drivers 0x80 00-1F linux/fb.h 0x81 00-1F linux/vduse.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 F0-FF linux/sockios.h SIOCDEVPRIVATE range 0x8A 00-1F linux/eventpoll.h 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 Btrfs filesystem and linux/fs.h some lifted to vfs/generic 0x97 00-7F fs/ceph/ioctl.h Ceph file system 0x99 00-0F 537-Addinboard driver mailto:[email protected] 0x9A 00-0F include/uapi/fwctl/fwctl.h 0xA0 all linux/sdp/sdp.h Industrial Device Project mailto:[email protected] 0xA1 0 linux/vtpm_proxy.h TPM Emulator Proxy Driver 0xA2 all uapi/linux/acrn.h ACRN hypervisor 0xA3 80-8F Port ACL in development: mailto:[email protected] 0xA3 90-9F linux/dtlk.h 0xA4 00-1F uapi/linux/tee.h Generic TEE subsystem 0xA4 00-1F uapi/asm/sgx.h mailto:[email protected] 0xA5 01-05 linux/surface_aggregator/cdev.h Microsoft Surface Platform System Aggregator mailto:[email protected] 0xA5 20-2F linux/surface_aggregator/dtx.h Microsoft Surface DTX driver mailto:[email protected] 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:[email protected] 0xAE 00-1F linux/kvm.h Kernel-based Virtual Machine mailto:[email protected] 0xAE 40-FF linux/kvm.h Kernel-based Virtual Machine mailto:[email protected] 0xAE 20-3F linux/nitro_enclaves.h Nitro Enclaves 0xAF 00-1F linux/fsl_hypervisor.h Freescale hypervisor 0xB0 all RATIO devices in development: mailto:[email protected] 0xB1 00-1F PPPoX mailto:[email protected] 0xB2 00 arch/powerpc/include/uapi/asm/papr-vpd.h powerpc/pseries VPD API mailto:[email protected] 0xB2 01-02 arch/powerpc/include/uapi/asm/papr-sysparm.h powerpc/pseries system parameter API mailto:[email protected] 0xB2 03-05 arch/powerpc/include/uapi/asm/papr-indices.h powerpc/pseries indices API mailto:[email protected] 0xB2 06-07 arch/powerpc/include/uapi/asm/papr-platform-dump.h powerpc/pseries Platform Dump API mailto:[email protected] 0xB2 08 arch/powerpc/include/uapi/asm/papr-physical-attestation.h powerpc/pseries Physical Attestation API mailto:[email protected] 0xB2 09 arch/powerpc/include/uapi/asm/papr-hvpipe.h powerpc/pseries HVPIPE API mailto:[email protected] 0xB3 00 linux/mmc/ioctl.h 0xB4 00-0F linux/gpio.h mailto:[email protected] 0xB5 00-0F uapi/linux/rpmsg.h mailto:[email protected] 0xB6 all linux/fpga-dfl.h 0xB7 all uapi/linux/remoteproc_cdev.h mailto:[email protected] 0xB7 all uapi/linux/nsfs.h <mailto:Andrei Vagin [email protected]> 0xB8 01-02 uapi/misc/mrvl_cn10k_dpi.h Marvell CN10K DPI driver 0xB8 all uapi/linux/mshv.h Microsoft Hyper-V /dev/mshv driver mailto:[email protected] 0xBA 00-0F uapi/linux/liveupdate.h Pasha Tatashin mailto:[email protected] 0xC0 00-0F linux/usb/iowarrior.h 0xCA 00-0F uapi/misc/cxl.h Dead since 6.15 0xCA 10-2F uapi/misc/ocxl.h 0xCA 80-BF uapi/scsi/cxlflash_ioctl.h Dead since 6.15 0xCB 00-1F CBM serial IEC bus in development: mailto:[email protected] 0xCC 00-0F drivers/misc/ibmvmc.h pseries VMC driver 0xCD 01 linux/reiserfs_fs.h Dead since 6.13 0xCE 01-02 uapi/linux/cxl_mem.h Compute Express Link Memory Devices 0xCF 02 fs/smb/client/cifs_ioctl.h 0xDD 00-3F ZFCP device driver see drivers/s390/scsi/ mailto:[email protected] 0xE5 00-3F linux/fuse.h 0xEC 00-01 drivers/platform/chrome/cros_ec_dev.h ChromeOS EC driver 0xEE 00-09 uapi/linux/pfrut.h Platform Firmware Runtime Update and Telemetry 0xF3 00-3F drivers/usb/misc/sisusbvga/sisusb.h sisfb (in development) mailto:[email protected] 0xF6 all LTTng Linux Trace Toolkit Next Generation mailto:[email protected] 0xF8 all arch/x86/include/uapi/asm/amd_hsmp.h AMD HSMP EPYC system management interface driver mailto:[email protected] 0xF9 00-0F uapi/misc/amd-apml.h AMD side band system management interface driver mailto:[email protected] 0xFD all linux/dm-ioctl.h 0xFE all linux/isst_if.h ==== ===== ========================================================= ================================================================