1.\" $NetBSD: ioctl.9,v 1.25 2008/05/02 21:46:19 martin Exp $ 2.\" 3.\" Copyright (c) 1999 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Heiko W.Rupp <hwr@pilhuhn.de> 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd December 7, 2001 31.Dt IOCTL 9 32.Os 33.Sh NAME 34.Nm ioctl 35.Nd "how to implement a new ioctl call to access device drivers" 36.Sh SYNOPSIS 37.In sys/ioctl.h 38.In sys/ioccom.h 39.Ft int 40.Fn ioctl "int" "unsigned long" "..." 41.Sh DESCRIPTION 42.Nm 43are internally defined as 44.Bl -tag -width define 45.It #define FOOIOCTL fun(t,n,pt) 46.El 47.Pp 48where the different variables and functions are: 49.Bl -tag -width FOOIOCTL 50.It Cm FOOIOCTL 51the name which will later be given in the 52.Xr ioctl 2 53system call as second argument, e.g., 54.Dl ioctl(s, FOOIOCTL, ...) . 55.It Fn fun 56a macro which can be one of 57.Bl -tag -width _IOWR 58.It _IO 59the call is a simple message to the kernel by itself. 60It does not copy anything into the kernel, nor does it want anything back. 61.It _IOR 62the call only reads parameters from the kernel and does not 63pass any to it 64.It _IOW 65the call only writes parameters to the kernel, but does not want anything 66back 67.It _IOWR 68the call writes data to the kernel and wants information back. 69.El 70.It Ar t 71This integer describes to which subsystem the ioctl applies. 72.Ar t 73can be one of 74.Bl -tag -width xxxxx -compact 75.It '1' 76pulse-per-second interface 77.It '4' 78.Xr isdn 4 79.It 'a' 80ISO networking 81.It 'A' 82ac devices (hp300) 83.It 'A' 84Advanced Power Management (hpcmips, i386, sparc), see 85.Xr apm 4 86.It 'A' 87ADB devices (mac68k, macppc) 88.It 'A' 89.Xr audio 4 90.It 'A' 91.Xr isdntel 4 92.It 'b' 93.Xr \&tb 4 94.It 'b' 95Bluetooth HCI sockets, see 96.Xr bluetooth 4 97.It 'b' 98Bluetooth Hub Control, see 99.Xr bthub 4 100.It 'b' 101Bluetooth SCO audio driver, see 102.Xr btsco 4 103.It 'B' 104bell device (x68k) 105.It 'B' 106.Xr bpf 4 107.It 'c' 108coda 109.It 'c' 110.Xr \&cd 4 111.It 'c' 112.Xr \&ch 4 113.It 'C' 114clock devices (amiga, atari, hp300, x68k) 115.It 'C' 116.Xr isdnctl 4 117.It 'd' 118the disk subsystem 119.It 'E' 120.Xr envsys 4 121.It 'f' 122files 123.It 'F' 124Sun-compatible framebuffers 125.It 'F' 126.Xr ccd 4 127and 128.Xr vnd 4 129.It 'g' 130qdss framebuffers 131.It 'G' 132grf devices (amiga, atari, hp300, mac68k, x68k) 133.It 'h' 134HIL devices (hp300) 135.It 'H' 136HIL devices (hp300) 137.It 'H' 138HPc framebuffers 139.It 'i' 140a (pseudo) interface 141.It 'I' 142.Xr ite 4 143(mac68k) 144.It 'J' 145ISA joystick interface 146.It 'k' 147Sun-compatible (and other) keyboards 148.It 'K' 149.Xr lkm 4 150.It 'l' 151leo devices (atari) 152.It 'm' 153.Xr mtio 4 154.It 'M' 155mouse devices (atari) 156.It 'M' 157.Xr mlx 4 158.It 'n' 159virtual console device (arm32) 160.It 'n' 161SMB networking 162.It 'O' 163OpenPROM and OpenFirmware 164.It 'p' 165power control (x68k) 166.It 'P' 167parallel port (amiga, x68k) 168.It 'P' 169profiling (arm32) 170.It 'P' 171printer/plotter interface (hp300) 172.It 'P' 173.Xr magma 4 174bpp (sparc) 175.It 'q' 176.Xr altq 9 177.It 'q' 178pmax graphics devices 179.It 'Q' 180.Xr altq 9 181.It 'Q' 182raw SCSI commands 183.It 'r' 184the routing subsystem 185.It 'r' 186.Xr \&md 4 187.It 'R' 188.Xr isdnbchan 4 189.It 'R' 190.Xr rnd 4 191.It 's' 192the socket layer 193.It 's' 194satlink devices 195.It 'S' 196SCSI disks (arc, hp300, pmax) 197.It 'S' 198watchdog devices (sh3) 199.It 'S' 200ISA speaker devices 201.It 'S' 202stic devices 203.It 'S' 204scanners 205.It 't' 206the tty layer 207.It 'u' 208user defined ??? 209.It 'U' 210scsibus (see 211.Xr scsi 4 ) 212.It 'v' 213Sun-compatible 214.Dq firm events 215.It 'V' 216view device (amiga, atari) 217.It 'V' 218sram device (x68k) 219.It 'w' 220watchdog devices 221.It 'W' 222wt devices 223.It 'W' 224wscons devices 225.It 'x' 226bt8xx devices 227.It 'Z' 228ite devices (amiga, atari, x68k) 229.It 'Z' 230passthrough ioctls 231.El 232.It Ar n 233This numbers the ioctl within the group. 234There may be only one 235.Ar n 236for a given 237.Ar t . 238This is a unsigned 8 bit number. 239.It Ar pt 240This specifies the type of the passed parameter. 241This one gets internally transformed to the size of the parameter, so 242for example, if you want to pass a structure, then you have to specify that 243structure and not a pointer to it or sizeof(struct foo) 244.El 245.Pp 246In order for the new ioctl to be known to the system it is installed 247in either \*[Lt]sys/ioctl.h\*[Gt] or one of the files that are reached from 248\*[Lt]sys/ioctl.h\*[Gt]. 249.Sh EXAMPLES 250.Bd -literal -offset indent 251#define FOOIOCTL _IOWR('i', 23, int) 252 253int a = 3; 254error = ioctl(s, FOOICTL, \*[Am]a); 255.Ed 256.Pp 257Within the ioctl()-routine of the driver, it can be then accessed like 258.Bd -literal -offset indent 259driver_ioctl(..., u_long cmd, void *data) 260{ 261 ... 262 switch (cmd) { 263 264 case FOOIOCTL: 265 int *a = (int *)data; 266 printf(" Value passed: %d\en", *a); 267 break; 268 } 269} 270.Ed 271.Sh NOTES 272Note that if you for example try to read information from an ethernet 273driver where the name of the card is included in the third argument 274(e.g., ioctl(s, READFROMETH, struct ifreq *)), then you have to use 275the _IOWR() form not the _IOR(), as passing the name of the card to the 276kernel already consists of writing data. 277.Sh RETURN VALUES 278All ioctl() routines should return either 0 or a defined error code. 279The use of magic numbers such as -1, to indicate that a given ioctl 280code was not handled is strongly discouraged. 281The value -1 coincides with the historic value for 282.Cm ERESTART 283which was shown to produce user space code that never returned from 284a call to 285.Xr ioctl 2 . 286.Pp 287For ioctl codes that 288are not handled by a given routine, the pseudo error value 289.Cm EPASSTHROUGH 290is provided. 291.Cm EPASSTHROUGH 292indicates that no error occurred during processing (it did not fail), 293but neither was anything processed (it did not succeed). 294This supersedes the use of either 295.Cm ENOTTY 296(which is an explicit failure) or -1 (which has no contextual meaning) 297as a return value. 298.Cm ENOTTY 299will get passed directly back to user space and bypass any further 300processing by other ioctl layers. 301Only code that wishes to suppress possible further processing of an 302ioctl code (e.g., the tty line discipline code) should return 303.Cm ENOTTY . 304All other code should return 305.Cm EPASSTHROUGH , 306even if it knows that no other layers will be called upon. 307.Pp 308If the value 309.Cm EPASSTHROUGH 310is returned to 311.Fn sys_ioctl , 312then it will there be changed to 313.Cm ENOTTY 314to be returned to user space, thereby providing the proper error 315notification to the application. 316.Sh SEE ALSO 317.Xr ioctl 2 318