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'). NOTE! Do NOT use 34sizeof(arg) as the third argument as this results in your ioctl thinking 35it passes an argument of type size_t. 36 37Some devices use their major number as the identifier; this is OK, as 38long as it is unique. Some devices are irregular and don't follow any 39convention at all. 40 41Following this convention is good because: 42 43(1) Keeping the ioctl's globally unique helps error checking: 44 if a program calls an ioctl on the wrong device, it will get an 45 error rather than some unexpected behaviour. 46 47(2) The 'strace' build procedure automatically finds ioctl numbers 48 defined with _IO, _IOW, _IOR, or _IOWR. 49 50(3) 'strace' can decode numbers back into useful names when the 51 numbers are unique. 52 53(4) People looking for ioctls can grep for them more easily when 54 this convention is used to define the ioctl numbers. 55 56(5) When following the convention, the driver code can use generic 57 code to copy the parameters between user and kernel space. 58 59This table lists ioctls visible from user land for Linux/i386. It contains 60most drivers up to 2.3.14, but I know I am missing some. 61 62Code Seq# Include File Comments 63======================================================== 640x00 00-1F linux/fs.h conflict! 650x00 00-1F scsi/scsi_ioctl.h conflict! 660x00 00-1F linux/fb.h conflict! 670x00 00-1F linux/wavefront.h conflict! 680x02 all linux/fd.h 690x03 all linux/hdreg.h 700x04 all linux/umsdos_fs.h 710x06 all linux/lp.h 720x09 all linux/md.h 730x12 all linux/fs.h 74 linux/blkpg.h 750x20 all drivers/cdrom/cm206.h 760x22 all scsi/sg.h 77'#' 00-3F IEEE 1394 Subsystem Block for the entire subsystem 78'1' 00-1F <linux/timepps.h> PPS kit from Ulrich Windl 79 <ftp://ftp.de.kernel.org/pub/linux/daemons/ntp/PPS/> 80'6' 00-10 <asm-i386/processor.h> Intel IA32 microcode update driver 81 <mailto:tigran@veritas.com> 82'8' all SNP8023 advanced NIC card 83 <mailto:mcr@solidum.com> 84'A' 00-1F linux/apm_bios.h 85'B' C0-FF advanced bbus 86 <mailto:maassen@uni-freiburg.de> 87'C' all linux/soundcard.h 88'D' all asm-s390/dasd.h 89'F' all linux/fb.h 90'I' all linux/isdn.h 91'J' 00-1F drivers/scsi/gdth_ioctl.h 92'K' all linux/kd.h 93'L' 00-1F linux/loop.h 94'L' E0-FF linux/ppdd.h encrypted disk device driver 95 <http://linux01.gwdg.de/~alatham/ppdd.html> 96'M' all linux/soundcard.h conflict! 97'M' 00-1F linux/isicom.h conflict! 98'N' 00-1F drivers/usb/scanner.h 99'P' all linux/soundcard.h 100'Q' all linux/soundcard.h 101'R' 00-1F linux/random.h 102'S' all linux/cdrom.h conflict! 103'S' 80-81 scsi/scsi_ioctl.h conflict! 104'S' 82-FF scsi/scsi.h conflict! 105'T' all linux/soundcard.h conflict! 106'T' all asm-i386/ioctls.h conflict! 107'U' 00-EF linux/drivers/usb/usb.h 108'U' F0-FF drivers/usb/auerswald.c 109'V' all linux/vt.h 110'W' 00-1F linux/watchdog.h conflict! 111'W' 00-1F linux/wanrouter.h conflict! 112'X' all linux/xfs_fs.h 113'Y' all linux/cyclades.h 114'a' all ATM on linux 115 <http://lrcwww.epfl.ch/linux-atm/magic.html> 116'b' 00-FF bit3 vme host bridge 117 <mailto:natalia@nikhefk.nikhef.nl> 118'c' 00-7F linux/comstats.h conflict! 119'c' 00-7F linux/coda.h conflict! 120'd' 00-1F linux/devfs_fs.h conflict! 121'd' 00-DF linux/video_decoder.h conflict! 122'd' F0-FF linux/digi1.h 123'e' all linux/digi1.h conflict! 124'e' 00-1F linux/video_encoder.h conflict! 125'e' 00-1F net/irda/irtty.h conflict! 126'f' 00-1F linux/ext2_fs.h 127'h' 00-7F Charon filesystem 128 <mailto:zapman@interlan.net> 129'i' 00-3F linux/i2o.h 130'j' 00-3F linux/joystick.h 131'k' all asm-sparc/kbio.h 132 asm-sparc64/kbio.h 133'l' 00-3F linux/tcfs_fs.h transparent cryptographic file system 134 <http://mikonos.dia.unisa.it/tcfs> 135'l' 40-7F linux/udf_fs_i.h in development: 136 <http://www.trylinux.com/projects/udf/> 137'm' all linux/mtio.h conflict! 138'm' all linux/soundcard.h conflict! 139'm' all linux/synclink.h conflict! 140'm' 00-1F net/irda/irmod.h conflict! 141'n' 00-7F linux/ncp_fs.h 142'n' E0-FF video/matrox.h matroxfb 143'p' 00-3F linux/mc146818rtc.h 144'p' 40-7F linux/nvram.h 145'p' 80-9F user-space parport 146 <mailto:tim@cyberelk.net> 147'q' 00-1F linux/videotext.h conflict! 148'q' 80-FF Internet PhoneJACK, Internet LineJACK 149 <http://www.quicknet.net> 150'r' 00-1F linux/msdos_fs.h 151's' all linux/cdk.h 152't' 00-7F linux/if_ppp.h 153't' 80-8F linux/isdn_ppp.h 154'u' 00-1F linux/smb_fs.h 155'v' 00-1F linux/ext2_fs.h conflict! 156'v' all linux/videodev.h conflict! 157'w' all CERN SCI driver 158'y' 00-1F packet based user level communications 159 <mailto:zapman@interlan.net> 160'z' 00-3F CAN bus card 161 <mailto:hdstich@connectu.ulm.circular.de> 162'z' 40-7F CAN bus card 163 <mailto:oe@port.de> 1640x80 00-1F linux/fb.h 1650x89 00-06 asm-i386/sockios.h 1660x89 0B-DF linux/sockios.h 1670x89 E0-EF linux/sockios.h SIOCPROTOPRIVATE range 1680x89 F0-FF linux/sockios.h SIOCDEVPRIVATE range 1690x8B all linux/wireless.h 1700x8C 00-3F WiNRADiO driver 171 <http://www.proximity.com.au/~brian/winradio/> 1720x90 00 drivers/cdrom/sbpcd.h 1730x93 60-7F linux/auto_fs.h 1740x99 00-0F 537-Addinboard driver 175 <mailto:buk@buks.ipn.de> 1760xA0 all linux/sdp/sdp.h Industrial Device Project 177 <mailto:kenji@bitgate.com> 1780xA3 80-8F Port ACL in development: 179 <mailto:tlewis@mindspring.com> 1800xA3 90-9F linux/dtlk.h 1810xAB 00-1F linux/nbd.h 1820xAC 00-1F linux/raw.h 1830xAD 00 Netfilter device in development: 184 <mailto:rusty@rustcorp.com.au> 1850xB0 all RATIO devices in development: 186 <mailto:vgo@ratio.de> 1870xB1 00-1F PPPoX <mailto:mostrows@styx.uwaterloo.ca> 1880xCB 00-1F CBM serial IEC bus in development: 189 <mailto:michael.klein@puffin.lb.shuttle.de> 190