314 lines
7.9 KiB
Groff
314 lines
7.9 KiB
Groff
.\" Copyright (c) 1999 Chris Costello
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.\" All rights reserved.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 5, 2010
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.Dt MAKE_DEV 9
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.Os
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.Sh NAME
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.Nm make_dev ,
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.Nm make_dev_cred ,
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.Nm make_dev_credf ,
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.Nm make_dev_alias ,
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.Nm destroy_dev ,
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.Nm destroy_dev_sched ,
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.Nm destroy_dev_sched_cb ,
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.Nm destroy_dev_drain ,
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.Nm dev_depends
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.Nd manage
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.Vt cdev Ns 's
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and DEVFS registration for devices
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/conf.h
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.Ft struct cdev *
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.Fn make_dev "struct cdevsw *cdevsw" "int unit" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
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.Ft struct cdev *
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.Fn make_dev_cred "struct cdevsw *cdevsw" "int unit" "struct ucred *cr" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
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.Ft struct cdev *
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.Fn make_dev_credf "int flags" "struct cdevsw *cdevsw" "int unit" "struct ucred *cr" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
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.Ft struct cdev *
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.Fn make_dev_alias "struct cdev *pdev" "const char *fmt" ...
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.Ft void
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.Fn destroy_dev "struct cdev *dev"
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.Ft void
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.Fn destroy_dev_sched "struct cdev *dev"
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.Ft void
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.Fn destroy_dev_sched_cb "struct cdev *dev" "void (*cb)(void *)" "void *arg"
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.Ft void
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.Fn destroy_dev_drain "struct cdevsw *csw"
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.Ft void
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.Fn dev_depends "struct cdev *pdev" "struct cdev *cdev"
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.Sh DESCRIPTION
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The
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.Fn make_dev_credf
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function creates a
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.Fa cdev
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structure for a new device.
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It also notifies
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.Xr devfs 5
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of the presence of the new device, that causes corresponding nodes
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to be created.
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Besides this, a
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.Xr devctl 4
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notification is sent.
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The device will be owned by
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.Va uid ,
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with the group ownership as
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.Va gid .
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The name is the expansion of
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.Va fmt
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and following arguments as
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.Xr printf 9
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would print it.
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The name determines its path under
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.Pa /dev
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or other
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.Xr devfs 5
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mount point and may contain slash
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.Ql /
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characters to denote subdirectories.
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The permissions of the file specified in
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.Va perms
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are defined in
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.In sys/stat.h :
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.Pp
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.Bd -literal -offset indent -compact
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#define S_IRWXU 0000700 /* RWX mask for owner */
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#define S_IRUSR 0000400 /* R for owner */
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#define S_IWUSR 0000200 /* W for owner */
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#define S_IXUSR 0000100 /* X for owner */
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#define S_IRWXG 0000070 /* RWX mask for group */
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#define S_IRGRP 0000040 /* R for group */
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#define S_IWGRP 0000020 /* W for group */
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#define S_IXGRP 0000010 /* X for group */
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#define S_IRWXO 0000007 /* RWX mask for other */
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#define S_IROTH 0000004 /* R for other */
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#define S_IWOTH 0000002 /* W for other */
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#define S_IXOTH 0000001 /* X for other */
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#define S_ISUID 0004000 /* set user id on execution */
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#define S_ISGID 0002000 /* set group id on execution */
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#define S_ISVTX 0001000 /* sticky bit */
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#ifndef _POSIX_SOURCE
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#define S_ISTXT 0001000
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#endif
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.Ed
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.Pp
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The
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.Va cr
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argument specifies credentials that will be stored in the
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.Fa si_cred
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member of the initialized
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.Fa struct cdev .
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The
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.Va flags
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argument alters the operation of
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.Fn make_dev_credf .
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The following values are currently accepted:
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.Pp
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.Bd -literal -offset indent -compact
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MAKEDEV_REF reference the created device
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MAKEDEV_NOWAIT do not sleep, may return NULL
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MAKEDEV_WAITOK allow the function to sleep to satisfy malloc
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MAKEDEV_ETERNAL created device will be never destroyed
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.Ed
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.Pp
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The
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.Dv MAKEDEV_WAITOK
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flag is assumed if none of
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.Dv MAKEDEV_WAITOK ,
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.Dv MAKEDEV_NOWAIT
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is specified.
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.Pp
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The
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.Xr dev_clone 9
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event handler shall specify
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.Dv MAKEDEV_REF
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flag when creating a device in response to lookup, to avoid race where
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the device created is destroyed immediately after
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.Xr devfs_lookup 9
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drops his reference to cdev.
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.Pp
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The
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.Dv MAKEDEV_ETERNAL
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flag allows the kernel to not acquire some locks when translating system
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calls into the cdevsw methods calls.
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It is responsibility of the driver author to make sure that
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.Fn destroy_dev
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is never called on the returned cdev.
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For the convenience, use the
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.Dv MAKEDEV_ETERNAL_KLD
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flag for the code that can be compiled into kernel or loaded
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(and unloaded) as loadable module.
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.Pp
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The
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.Fn make_dev_cred
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function is equivalent to the call
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.Bd -literal -offset indent
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make_dev_credf(0, cdevsw, unit, cr, uid, gid, perms, fmt, ...);
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.Ed
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.Pp
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The
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.Fn make_dev
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function call is the same as
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.Bd -literal -offset indent
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make_dev_credf(0, cdevsw, unit, NULL, uid, gid, perms, fmt, ...);
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.Ed
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.Pp
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The
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.Fn make_dev_alias
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function takes the returned
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.Ft cdev
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from
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.Fn make_dev
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and makes another (aliased) name for this device.
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It is an error to call
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.Fn make_dev_alias
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prior to calling
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.Fn make_dev .
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.Pp
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The
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.Fa cdev
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returned by
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.Fn make_dev
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and
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.Fn make_dev_alias
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has two fields,
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.Fa si_drv1
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and
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.Fa si_drv2 ,
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that are available to store state.
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Both fields are of type
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.Ft void * .
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These are designed to replace the
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.Fa unit
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argument to
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.Fn make_dev ,
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which can be obtained with
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.Fn dev2unit .
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.Pp
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The
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.Fn destroy_dev
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function takes the returned
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.Fa cdev
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from
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.Fn make_dev
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and destroys the registration for that device.
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The notification is sent to
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.Xr devctl 4
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about the destruction event.
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Do not call
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.Fn destroy_dev
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on devices that were created with
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.Fn make_dev_alias .
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.Pp
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The
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.Fn dev_depends
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function establishes a parent-child relationship between two devices.
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The net effect is that a
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.Fn destroy_dev
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of the parent device will also result in the destruction of the
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child device(s),
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if any exist.
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A device may simultaneously be a parent and a child,
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so it is possible to build a complete hierarchy.
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.Pp
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The
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.Fn destroy_dev_sched_cb
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function schedules execution of the
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.Fn destroy_dev
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for the specified
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.Fa cdev
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in the safe context.
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After
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.Fn destroy_dev
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is finished, and if the supplied
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.Fa cb
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is not NULL, the callback
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.Fa cb
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is called, with argument
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.Fa arg .
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The
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.Fn destroy_dev_sched
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function is the same as
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.Bd -literal -offset indent
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destroy_dev_sched_cb(cdev, NULL, NULL);
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.Ed
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.Pp
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The
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.Fn d_close
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driver method cannot call
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.Fn destroy_dev
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directly. Doing so causes deadlock when
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.Fn destroy_dev
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waits for all threads to leave the driver methods.
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Also, because
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.Fn destroy_dev
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sleeps, no non-sleepable locks may be held over the call.
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The
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.Fn destroy_dev_sched
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family of functions overcome these issues.
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.Pp
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The device driver may call the
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.Fn destroy_dev_drain
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function to wait until all devices that have supplied
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.Fa csw
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as cdevsw, are destroyed. This is useful when driver knows that
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.Fn destroy_dev_sched
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is called for all instantiated devices, but need to postpone module
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unload until
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.Fn destroy_dev
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is actually finished for all of them.
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.Pp
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.Sh SEE ALSO
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.Xr devctl 4 ,
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.Xr destroy_dev_drain 9 ,
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.Xr dev_clone 9 ,
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.Xr devfs 5
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.Sh HISTORY
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The
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.Fn make_dev
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and
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.Fn destroy_dev
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functions first appeared in
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.Fx 4.0 .
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The function
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.Fn make_dev_alias
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first appeared in
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.Fx 4.1 .
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The function
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.Fn dev_depends
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first appeared in
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.Fx 5.0 .
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The functions
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.Fn make_dev_credf ,
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.Fn destroy_dev_sched ,
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.Fn destroy_dev_sched_cb
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first appeared in
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.Fx 7.0 .
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