6 If you are adding new ioctl's to the kernel, you should use the _IO
7 macros defined in <linux/ioctl.h>:
9 _IO an ioctl with no parameters
10 _IOW an ioctl with write parameters (from user's point of view)
11 _IOR an ioctl with read parameters (from user's point of view)
12 _IOWR an ioctl with both write and read parameters.
14 'Write' and 'read' are from the user's point of view. This is like the
15 system calls 'write' and 'read'. For example, a SET_FOO ioctl would be
16 _IOW, although the kernel would actually read data from user space; a
17 GET_FOO ioctl would be _IOR, although the kernel would actually write
20 The first argument to _IO, _IOW, _IOR, or _IOWR is an identifying letter
21 or number from the table below. If you are writing a driver for a new
22 device and need a letter, pick an unused letter. You can register the
23 letter by patching this file and submitting the patch to Linus Torvalds.
24 Or you can e-mail me at <mec@shout.net> and I'll register one for you.
26 The second argument to _IO, _IOW, _IOR, or _IOWR is a sequence number
27 to distinguish ioctls from each other. The third argument is the size
28 of the structure going into the kernel or coming out of the kernel.
30 Some devices use their major number as the identifier; this is not
31 recommended. Some devices are even more irregular and don't follow
32 the convention at all.
34 Following the convention is good because:
36 (1) Keeping the ioctl's globally unique helps error checking:
37 if a program calls an ioctl on the wrong device, it will get an
38 error rather than some unexpected behaviour.
40 (2) The 'strace' build procedure automatically finds ioctl numbers
41 defined with _IO, _IOW, _IOR, or _IOWR.
43 (3) 'strace' can decode numbers back into useful names when the
46 (4) People looking for ioctls can grep for them more easily when
47 the convention is used to define the ioctl numbers.
49 (5) When following the convention, the driver code can use generic
50 code to call verify_area to validate parameters.
52 This table lists ioctls visible from user land for Linux/i386. It is
53 current to Linux 2.1.15.
55 Code Seq# Include File Comments
56 ========================================================
57 0x00 01-02 linux/fs.h conflict!
58 0x00 01-04 scsi/scsi_ioctl.h conflict!
60 0x03 all linux/hdreg.h
61 0x04 all linux/umsdos_fs.h
65 0x20 all linux/cm206.h
67 'A' all linux/apm_bios.h
68 'C' all linux/soundcard.h
73 'M' all linux/soundcard.h
74 'P' all linux/soundcard.h
75 'Q' all linux/soundcard.h
76 'R' all linux/random.h
77 'S' 00-7F linux/cdrom.h
78 'S' 80-81 scsi/scsi_ioctl.h
80 'T' all linux/soundcard.h conflict!
81 'T' all asm-i386/ioctls.h conflict!
83 'W' 00-1F linux/router.h conflict [Please reallocate]
84 'W' 00-1F linux/watchdog.h
85 'W' 20-27 linux/octal-relay.h in development
86 'W' 28-2F linux/iso16-relay.h in development
87 'Y' all linux/cyclades.h
88 'a' all various, see http://lrcwww.epfl.ch/linux-atm/magic.html
89 'b' 00-FF bit3 vme host bridge in development:
90 <mailto:natalia@nikhefk.nikhef.nl>
91 'c' all linux/comstats.h
92 'f' all linux/ext2_fs.h
93 'j' 00-3F linux/joystick.h
94 'k' all asm-sparc/kbio.h, asm-sparc64/kbio.h
95 'l' 00-3F linux/tcfs_fs.h in development:
96 <http://mikonos.dia.unisa.it/tcfs>
97 'm' all linux/mtio.h conflict!
98 'm' all linux/soundcard.h conflict!
99 'n' all linux/ncp_fs.h
100 'p' 00-3F linux/mc146818rtc.h
101 'p' 40-7F linux/nvram.h
102 'p' 80-9F user-space parport in development:
103 <tim@cyberelk.demon.co.uk>
104 'r' all linux/msdos_fs.h
106 't' 00-7F linux/if_ppp.h
107 't' 80-8F linux/isdn_ppp.h
108 'u' all linux/smb_fs.h
109 'v' all linux/ext2_fs.h
110 'w' all CERN SCI driver in development
111 'z' 00-3F CAN bus card in development:
112 <mailto:hdstich@connectu.ulm.circular.de>
113 'z' 40-7F CAN bas card in development:
115 0x89 00-0F asm-i386/sockios.h
116 0x89 10-DF linux/sockios.h
117 0x89 E0-EF linux/sockios.h SIOCPROTOPRIVATE range
118 0x89 F0-FF linux/sockios.h SIOCDEVPRIVATE range
119 0x8B all linux/wireless.h
120 0x8C 00-3F WiNRADiO driver in development:
121 <http://www.proximity.com.au/~brian/winradio/>
122 0x90 00 linux/sbpcd.h
123 0x93 60-7F linux/auto_fs.h
124 0x99 00-0F 537-Addinboard driver in development:
125 <mailto:b.kohl@ipn-b.comlink.apc.org>
126 0xA0 all Small Device Project in development:
127 <mailto:khollis@northwest.com>
128 0xA3 80-8F Port ACL in development:
129 <mailto:tlewis@mindspring.com>
130 0xA3 90-9F DoubleTalk driver in development:
131 <mailto:jrv@vanzandt.mv.com>
132 0xAB 00-06 Network block device