1Ioctl Numbers 219 October 1999 3Michael Elizabeth Chastain 4<mec@shout.net> 5 6If you are adding new ioctl's to the kernel, you should use the _IO 7macros defined in <linux/ioctl.h>: 8 9 _IO an ioctl with no parameters 10 _IOW an ioctl with write parameters (copy_from_user) 11 _IOR an ioctl with read parameters (copy_to_user) 12 _IOWR an ioctl with both write and read parameters. 13 14'Write' and 'read' are from the user's point of view, just like the 15system calls 'write' and 'read'. For example, a SET_FOO ioctl would 16be _IOW, although the kernel would actually read data from user space; 17a GET_FOO ioctl would be _IOR, although the kernel would actually write 18data to user space. 19 20The first argument to _IO, _IOW, _IOR, or _IOWR is an identifying letter 21or number from the table below. Because of the large number of drivers, 22many drivers share a partial letter with other drivers. 23 24If you are writing a driver for a new device and need a letter, pick an 25unused block with enough room for expansion: 32 to 256 ioctl commands. 26You can register the block by patching this file and submitting the 27patch to Linus Torvalds. Or you can e-mail me at <mec@shout.net> and 28I'll register one for you. 29 30The second argument to _IO, _IOW, _IOR, or _IOWR is a sequence number 31to distinguish ioctls from each other. The third argument to _IOW, 32_IOR, or _IOWR is the type of the data going into the kernel or coming 33out of the kernel (e.g. 'int' or 'struct foo'). 34 35Some devices use their major number as the identifier; this is OK, as 36long as it is unique. Some devices are irregular and don't follow any 37convention at all. 38 39Following this convention is good because: 40 41(1) Keeping the ioctl's globally unique helps error checking: 42 if a program calls an ioctl on the wrong device, it will get an 43 error rather than some unexpected behaviour. 44 45(2) The 'strace' build procedure automatically finds ioctl numbers 46 defined with _IO, _IOW, _IOR, or _IOWR. 47 48(3) 'strace' can decode numbers back into useful names when the 49 numbers are unique. 50 51(4) People looking for ioctls can grep for them more easily when 52 this convention is used to define the ioctl numbers. 53 54(5) When following the convention, the driver code can use generic 55 code to copy the parameters between user and kernel space. 56 57This table lists ioctls visible from user land for Linux/i386. It contains 58most drivers up to 2.3.14, but I know I am missing some. 59 60Code Seq# Include File Comments 61======================================================== 620x00 00-1F linux/fs.h conflict! 630x00 00-1F scsi/scsi_ioctl.h conflict! 640x00 00-1F linux/fb.h conflict! 650x00 00-1F linux/wavefront.h conflict! 660x02 all linux/fd.h 670x03 all linux/hdreg.h 680x04 all linux/umsdos_fs.h 690x06 all linux/lp.h 700x09 all linux/md.h 710x12 all linux/fs.h 72 linux/blkpg.h 730x20 all drivers/cdrom/cm206.h 740x22 all scsi/sg.h 75'1' 00-1F <linux/timepps.h> PPS kit from Ulrich Windl 76 <ftp://ftp.de.kernel.org/pub/linux/daemons/ntp/PPS/> 77'6' 00-10 <asm-i386/processor.h> Intel IA32 microcode update driver 78 <mailto:tigran@veritas.com> 79'8' all SNP8023 advanced NIC card 80 <mailto:mcr@solidum.com> 81'A' 00-1F linux/apm_bios.h 82'B' C0-FF advanced bbus 83 <mailto:maassen@uni-freiburg.de> 84'C' all linux/soundcard.h 85'D' all asm-s390/dasd.h 86'F' all linux/fb.h 87'I' all linux/isdn.h 88'J' 00-1F drivers/scsi/gdth_ioctl.h 89'K' all linux/kd.h 90'L' 00-1F linux/loop.h 91'L' E0-FF linux/ppdd.h encrypted disk device driver 92 <http://linux01.gwdg.de/~alatham/ppdd.html> 93'M' all linux/soundcard.h conflict! 94'M' 00-1F linux/isicom.h conflict! 95'N' 00-1F drivers/usb/scanner.h 96'P' all linux/soundcard.h 97'Q' all linux/soundcard.h 98'R' 00-1F linux/random.h 99'S' all linux/cdrom.h conflict! 100'S' 80-81 scsi/scsi_ioctl.h conflict! 101'S' 82-FF scsi/scsi.h conflict! 102'T' all linux/soundcard.h conflict! 103'T' all asm-i386/ioctls.h conflict! 104'U' all linux/drivers/usb/usb.h 105'V' all linux/vt.h 106'W' 00-1F linux/watchdog.h conflict! 107'W' 00-1F linux/wanrouter.h conflict! 108'X' all linux/xfs_fs.h 109'Y' all linux/cyclades.h 110'a' all ATM on linux 111 <http://lrcwww.epfl.ch/linux-atm/magic.html> 112'b' 00-FF bit3 vme host bridge 113 <mailto:natalia@nikhefk.nikhef.nl> 114'c' 00-7F linux/comstats.h conflict! 115'c' 00-7F linux/coda.h conflict! 116'd' 00-1F linux/devfs_fs.h conflict! 117'd' 00-DF linux/video_decoder.h conflict! 118'd' F0-FF linux/digi1.h 119'e' all linux/digi1.h conflict! 120'e' 00-1F linux/video_encoder.h conflict! 121'e' 00-1F net/irda/irtty.h conflict! 122'f' 00-1F linux/ext2_fs.h 123'h' 00-7F Charon filesystem 124 <mailto:zapman@interlan.net> 125'i' 00-3F linux/i2o.h 126'j' 00-3F linux/joystick.h 127'k' all asm-sparc/kbio.h 128 asm-sparc64/kbio.h 129'l' 00-3F linux/tcfs_fs.h transparent cryptographic file system 130 <http://mikonos.dia.unisa.it/tcfs> 131'l' 40-7F linux/udf_fs_i.h in development: 132 <http://www.trylinux.com/projects/udf/> 133'm' all linux/mtio.h conflict! 134'm' all linux/soundcard.h conflict! 135'm' all linux/synclink.h conflict! 136'm' 00-1F net/irda/irmod.h conflict! 137'n' 00-7F linux/ncp_fs.h 138'n' E0-FF video/matrox.h matroxfb 139'p' 00-3F linux/mc146818rtc.h 140'p' 40-7F linux/nvram.h 141'p' 80-9F user-space parport 142 <mailto:tim@cyberelk.net> 143'q' 00-1F linux/videotext.h conflict! 144'q' 80-FF Internet PhoneJACK, Internet LineJACK 145 <http://www.quicknet.net> 146'r' 00-1F linux/msdos_fs.h 147's' all linux/cdk.h 148't' 00-7F linux/if_ppp.h 149't' 80-8F linux/isdn_ppp.h 150'u' 00-1F linux/smb_fs.h 151'v' 00-1F linux/ext2_fs.h conflict! 152'v' all linux/videodev.h conflict! 153'w' all CERN SCI driver 154'y' 00-1F packet based user level communications 155 <mailto:zapman@interlan.net> 156'z' 00-3F CAN bus card 157 <mailto:hdstich@connectu.ulm.circular.de> 158'z' 40-7F CAN bus card 159 <mailto:oe@port.de> 1600x80 00-1F linux/fb.h 1610x89 00-06 asm-i386/sockios.h 1620x89 0B-DF linux/sockios.h 1630x89 E0-EF linux/sockios.h SIOCPROTOPRIVATE range 1640x89 F0-FF linux/sockios.h SIOCDEVPRIVATE range 1650x8B all linux/wireless.h 1660x8C 00-3F WiNRADiO driver 167 <http://www.proximity.com.au/~brian/winradio/> 1680x90 00 drivers/cdrom/sbpcd.h 1690x93 60-7F linux/auto_fs.h 1700x99 00-0F 537-Addinboard driver 171 <mailto:buk@buks.ipn.de> 1720xA0 all linux/sdp/sdp.h Industrial Device Project 173 <mailto:kenji@bitgate.com> 1740xA3 80-8F Port ACL in development: 175 <mailto:tlewis@mindspring.com> 1760xA3 90-9F linux/dtlk.h 1770xAB 00-1F linux/nbd.h 1780xAC 00-1F linux/raw.h 1790xAD 00 Netfilter device in development: 180 <mailto:rusty@rustcorp.com.au> 1810xB0 all RATIO devices in development: 182 <mailto:vgo@ratio.de> 1830xB1 00-1F PPPoX <mailto:mostrows@styx.uwaterloo.ca> 1840xCB 00-1F CBM serial IEC bus in development: 185 <mailto:michael.klein@puffin.lb.shuttle.de> 1860xF3 00-3F linux/sisfb.h SiS framebuffer device driver 187 <mailto:thomas@winischhofer.net> 1880xFE 00-9F Logical Volume Manager <mailto:linux-lvm@sistina.com> 189