FreeBSD-5.3/share/man/man9/device_ids.9

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.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\" $FreeBSD: src/share/man/man9/device_ids.9,v 1.3 2004/06/22 20:18:15 le Exp $
.\"
.Dd June 22, 2004
.Dt DEVICE_IDS 9
.Os
.Sh NAME
.Nm device_ids ,
.Nm major ,
.Nm minor ,
.Nm umajor ,
.Nm uminor
.Nd "calculate device ids"
.Sh SYNOPSIS
.In sys/types.h
.In sys/systm.h
.Ft int
.Fn major "struct cdev *dev"
.Ft int
.Fn minor "struct cdev *dev"
.Ft int
.Fn umajor "dev_t id"
.Ft int
.Fn uminor "dev_t id"
.Sh DESCRIPTION
The
.Nm
family of functions take either the raw device ID,
.Fa id ,
or a pointer to the device structure,
.Fa dev ,
and return the integer
value that is the major or minor device ID as requested.
.Pp
The actual major and minor device IDs are values masked from of the raw device ID.
For details on the actual calculations used to determine the major or minor IDs see
the actual source in
.Pa kern_conf.c .
.Sh RETURN VALUES
An integer greater than zero and less than
.Dv NUMCDEVSW .
.Fn major
and
.Fn minor
will return
.Dv NODEV
if the device is invalid.
.Sh AUTHORS
This manual page was written by
.An Chad David Aq davidc@acns.ab.ca .