316 lines
7.6 KiB
Groff
316 lines
7.6 KiB
Groff
.\" $NetBSD: ioctl.9,v 1.20 2003/05/01 08:42:08 uebayasi Exp $
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.\"
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.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Heiko W.Rupp <hwr@pilhuhn.de>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of the The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd December 7, 2001
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.Dt IOCTL 9
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.Os
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.Sh NAME
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.Nm ioctl
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.Nd "how to implement a new ioctl call to access device drivers"
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.Sh SYNOPSIS
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.In sys/ioctl.h
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.In sys/ioccom.h
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.Ft int
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.Fn ioctl "int" "unsigned long" "..."
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.Sh DESCRIPTION
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.Nm
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are internally defined as
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.Bl -tag -width define
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.It #define FOOIOCTL fun(t,n,pt)
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.El
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.Pp
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where the different variables and functions are:
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.Bl -tag -width FOOIOCTL
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.It Cm FOOIOCTL
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the name which will later be given in the
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.Xr ioctl 2
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system call as second argument, e.g.,
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.Dl ioctl(s, FOOIOCTL, ...) .
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.It Fn fun
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a macro which can be one of
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.Bl -tag -width _IOWR
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.It _IO
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the call is a simple message to the kernel by itself.
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It does not copy anything into the kernel, nor does it want anything back.
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.It _IOR
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the call only reads parameters from the kernel and does not
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pass any to it
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.It _IOW
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the call only writes parameters to the kernel, but does not want anything
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back
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.It _IOWR
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the call writes data to the kernel and wants information back.
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.El
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.It Ar t
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This integer describes to which subsystem the ioctl applies.
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.Ar t
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can be one of
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.Bl -tag -width xxxxx -compact
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.It '1'
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pulse-per-second interface
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.It '4'
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.Xr isdn 4
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.It 'a'
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ISO networking
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.It 'A'
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ac devices (hp300)
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.It 'A'
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Advanced Power Management (hpcmips, i386, sparc), see
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.Xr apm 4
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.It 'A'
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ADB devices (mac68k, macppc)
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.It 'A'
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.Xr audio 4
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.It 'A'
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.Xr isdntel 4
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.It 'b'
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.Xr \&tb 4
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.It 'B'
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bell device (x68k)
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.It 'B'
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.Xr bpf 4
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.It 'c'
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coda
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.It 'c'
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.Xr \&cd 4
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.It 'c'
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.Xr \&ch 4
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.It 'C'
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clock devices (amiga, atari, hp300, x68k)
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.It 'C'
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.Xr isdnctl 4
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.It 'd'
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the disk subsystem
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.It 'E'
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.Xr envsys 4
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.It 'f'
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files
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.It 'F'
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Sun-compatible framebuffers
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.It 'F'
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.Xr ccd 4
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and
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.Xr vnd 4
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.It 'g'
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qdss framebuffers
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.It 'G'
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grf devices (amiga, atari, hp300, mac68k, x68k)
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.It 'h'
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HIL devices (hp300)
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.It 'H'
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HIL devices (hp300)
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.It 'H'
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HPc framebuffers
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.It 'i'
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a (pseudo) interface
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.It 'I'
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.Xr ite 4
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(mac68k)
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.It 'J'
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ISA joystick interface
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.It 'k'
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Sun-compatible (and other) keyboards
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.It 'K'
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.Xr lkm 4
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.It 'l'
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leo devices (atari)
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.It 'm'
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.Xr mtio 4
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.It 'M'
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mouse devices (atari)
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.It 'M'
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.Xr mlx 4
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.It 'n'
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virtual console device (arm32)
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.It 'n'
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SMB networking
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.It 'O'
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OpenPROM and OpenFirmware
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.It 'p'
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power control (x68k)
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.It 'P'
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parallel port (amiga, x68k)
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.It 'P'
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profiling (arm32)
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.It 'P'
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printer/plotter interface (hp300)
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.It 'P'
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.Xr magma 4
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bpp (sparc)
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.It 'q'
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.Xr altq 9
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.It 'q'
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pmax graphics devices
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.It 'Q'
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.Xr altq 9
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.It 'Q'
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raw SCSI commands
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.It 'r'
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the routing subsystem
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.It 'r'
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.Xr \&md 4
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.It 'R'
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.Xr isdnbchan 4
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.It 'R'
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.Xr rnd 4
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.It 's'
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the socket layer
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.It 's'
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satlink devices
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.It 'S'
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SCSI disks (arc, hp300, pmax)
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.It 'S'
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watchdog devices (sh3)
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.It 'S'
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ISA speaker devices
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.It 'S'
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stic devices
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.It 'S'
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scanners
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.It 't'
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the tty layer
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.It 'u'
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user defined ???
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.It 'U'
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scsibus (see
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.Xr scsi 4 )
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.It 'v'
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Sun-compatible
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.Dq firm events
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.It 'V'
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view device (amiga, atari)
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.It 'V'
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sram device (x68k)
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.It 'w'
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watchdog devices
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.It 'W'
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wt devices
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.It 'W'
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wscons devices
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.It 'x'
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bt8xx devices
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.It 'Z'
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ite devices (amiga, atari, x68k)
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.It 'Z'
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passthrough ioctls
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.El
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.It Ar n
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This numbers the ioctl within the group.
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There may be only one
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.Ar n
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for a given
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.Ar t .
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This is a unsigned 8 bit number.
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.It Ar pt
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This specifies the type of the passed parameter.
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This one gets internally transformed to the size of the parameter, so
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for example, if you want to pass a structure, then you have to specify that
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structure and not a pointer to it or sizeof(struct foo)
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.El
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.Pp
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In order for the new ioctl to be known to the system it is installed
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in either \*[Lt]sys/ioctl.h\*[Gt] or one of the files that are reached from
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\*[Lt]sys/ioctl.h\*[Gt].
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.Sh EXAMPLES
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.Bd -literal -offset indent
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#define FOOIOCTL _IOWR('i', 23, int)
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int a = 3;
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error = ioctl(s, FOOICTL, \*[Am]a);
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.Ed
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.Pp
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Within the ioctl()-routine of the driver, it can be then accessed like
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.Bd -literal -offset indent
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driver_ioctl(..., u_long cmd, caddr_t data)
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{
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...
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switch (cmd) {
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case FOOIOCTL:
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int *a = (int *)data;
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printf(" Value passed: %d\en", *a);
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break;
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}
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}
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.Ed
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.Sh NOTES
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Note that if you for example try to read information from an ethernet
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driver where the name of the card is included in the third argument
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(e.g., ioctl(s, READFROMETH, struct ifreq *)), then you have to use
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the _IOWR() form not the _IOR(), as passing the name of the card to the
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kernel already consists of writing data.
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.Sh RETURN VALUES
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All ioctl() routines should return either 0 or a defined error code.
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The use of magic numbers such as -1, to indicate that a given ioctl
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code was not handled is strongly discouraged.
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The value -1 coincides with the historic value for
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.Cm ERESTART
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which was shown to produce user space code that never returned from
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a call to
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.Xr ioctl 2 .
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.Pp
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For ioctl codes that
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are not handled by a given routine, the pseudo error value
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.Cm EPASSTHROUGH
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is provided.
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.Cm EPASSTHROUGH
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indicates that no error occurred during processing (it did not fail),
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but neither was anything processed (it did not succeed).
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This supercedes the use of either
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.Cm ENOTTY
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(which is an explicit failure) or -1 (which has no contextual meaning)
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as a return value.
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.Cm ENOTTY
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will get passed directly back to user space and bypass any further
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processing by other ioctl layers.
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Only code that wishes to suppress possible further processing of an
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ioctl code (e.g., the tty line discipline code) should return
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.Cm ENOTTY .
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All other code should return
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.Cm EPASSTHROUGH ,
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even if it knows that no other layers will be called upon.
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.Pp
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If the value
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.Cm EPASSTHROUGH
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is returned to
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.Fn sys_ioctl ,
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then it will there be changed to
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.Cm ENOTTY
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to be returned to user space, thereby providing the proper error
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notification to the application.
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.Sh SEE ALSO
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.Xr ioctl 2
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