130 lines
4.3 KiB
Groff
130 lines
4.3 KiB
Groff
.\" $NetBSD: ioctl.9,v 1.6 2001/04/09 17:12:28 wiz 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 March 7, 1999
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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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.Fd #include <sys/ioctl.h>
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.Fd #include <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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where the different wariables and funcions are:
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.Bl -tag -width FOOIOCTL
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.It Fn FOOIOCTL
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the name as the ioctl is later known in a as second argument to a
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.Xr ioctl 2
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system call. E.g. 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 -withh _IOWR
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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 t
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This integer describes to which subsystem the ioctl applies.
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T
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can be one of
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.Bl -tag -width 'a'
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.It 'd' the disk subsystem
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.It 'f' files
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.It 'i' a (pseudo) interface
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.It 'r' the routing subsystem
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.It 's' the socket layer
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.It 't' the tty layer
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.It 'u' user defined ???
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.El
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.It n
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This numbers the ioctl within the group. There may be only one
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.Fn n
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for a given
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.Fn t .
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This is a unsigned 8 bit number.
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.It pt
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This specifyies the type of the passed parameter. This one gets internally
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transformed to the size of the parameter, so if you e.g. want to pass
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a structure, then you have to specify that structure and not a pointer
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to it or sizeof(struct foo)
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.El
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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 <sys/ioctl.h> or one of the files that are reached from
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<sys/ioctl.h>.
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.Sh EXAMPLE
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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, &a);
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Within the ioctl()-routine of the driver, it can be then accessd like
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driver_ioctl(..,cmd,data)
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u_long cmd;
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caddr_t data;
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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\n",a);
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}
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.Sh NOTES
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Note that if you e.g. try to read information from e.g. a 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 SEE ALSO
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.Xr ioctl 2
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