xref: /freebsd/share/man/man9/make_dev.9 (revision 66c6ebfe6bb9130df0ac65e100fd5e8f0a2efd1e)

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.Dd September 28, 2008
.Os
.Dt MAKE_DEV 9
.Sh NAME
.Nm make_dev ,
.Nm make_dev_cred ,
.Nm make_dev_credf ,
.Nm make_dev_alias ,
.Nm destroy_dev ,
.Nm destroy_dev_sched ,
.Nm destroy_dev_sched_cb ,
.Nm destroy_dev_drain ,
.Nm dev_depends
.Nd manage
.Vt cdev Ns 's
and DEVFS registration for devices
.Sh SYNOPSIS
.In sys/param.h
.In sys/conf.h
.Ft struct cdev *
.Fn make_dev "struct cdevsw *cdevsw" "int unit" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
.Ft struct cdev *
.Fn make_dev_cred "struct cdevsw *cdevsw" "int unit" "struct ucred *cr" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
.Ft struct cdev *
.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" ...
.Ft struct cdev *
.Fn make_dev_alias "struct cdev *pdev" "const char *fmt" ...
.Ft void
.Fn destroy_dev "struct cdev *dev"
.Ft void
.Fn destroy_dev_sched "struct cdev *dev"
.Ft void
.Fn destroy_dev_sched_cb "struct cdev *dev" "void (*cb)(void *)" "void *arg"
.Ft void
.Fn destroy_dev_drain "struct cdevsw *csw"
.Ft void
.Fn dev_depends "struct cdev *pdev" "struct cdev *cdev"
.Sh DESCRIPTION
The
.Fn make_dev_credf
function creates a
.Fa cdev
structure for a new device.
It also notifies
.Xr devfs 5
of the presence of the new device, that causes corresponding nodes
to be created.
Besides this, a
.Xr devctl 4
notification is sent.
The device will be owned by
.Va uid ,
with the group ownership as
.Va gid .
The name is the expansion of
.Va fmt
and following arguments as
.Xr printf 9
would print it.
The name determines its path under
.Pa /dev
or other
.Xr devfs 5
mount point and may contain slash
.Ql /
characters to denote subdirectories.
The permissions of the file specified in
.Va perms
are defined in
.In sys/stat.h :
.Pp
.Bd -literal -offset indent -compact
#define S_IRWXU 0000700    /* RWX mask for owner */
#define S_IRUSR 0000400    /* R for owner */
#define S_IWUSR 0000200    /* W for owner */
#define S_IXUSR 0000100    /* X for owner */

#define S_IRWXG 0000070    /* RWX mask for group */
#define S_IRGRP 0000040    /* R for group */
#define S_IWGRP 0000020    /* W for group */
#define S_IXGRP 0000010    /* X for group */

#define S_IRWXO 0000007    /* RWX mask for other */
#define S_IROTH 0000004    /* R for other */
#define S_IWOTH 0000002    /* W for other */
#define S_IXOTH 0000001    /* X for other */

#define S_ISUID 0004000    /* set user id on execution */
#define S_ISGID 0002000    /* set group id on execution */
#define S_ISVTX 0001000    /* sticky bit */
#ifndef _POSIX_SOURCE
#define S_ISTXT 0001000
#endif
.Ed
.Pp
The
.Va cr
argument specifies credentials that will be stored in the
.Fa si_cred
member of the initialized
.Fa struct cdev .
The
.Va flags
argument alters the operation of
.Fn make_dev_credf .
The following values are currently accepted:
.Pp
.Bd -literal -offset indent -compact
MAKEDEV_REF	reference the created device
.Ed
.Pp
The
.Xr dev_clone 9
event handler shall specify
.Dv MAKEDEV_REF
flag when creating a device in response to lookup, to avoid race where
the device created is destroyed immediately after
.Xr devfs_lookup 9
drops his reference to cdev.
.Pp
The
.Fn make_dev_cred
function is equivalent to the call
.Bd -literal -offset indent
make_dev_credf(0, cdevsw, unit, cr, uid, gid, perms, fmt, ...);
.Ed .
.Pp
The
.Fn make_dev
function call is the same as
.Bd -literal -offset indent
make_dev_credf(0, cdevsw, unit, NULL, uid, gid, perms, fmt, ...);
.Ed .
.Pp
The
.Fn make_dev_alias
function takes the returned
.Ft cdev
from
.Fn make_dev
and makes another (aliased) name for this device.
It is an error to call
.Fn make_dev_alias
prior to calling
.Fn make_dev .
.Pp
The
.Fa cdev
returned by
.Fn make_dev
and
.Fn make_dev_alias
has two fields,
.Fa si_drv1
and
.Fa si_drv2 ,
that are available to store state.
Both fields are of type
.Ft void * .
These are designed to replace the
.Fa unit
argument to
.Fn make_dev ,
which can be obtained with
.Fn dev2unit .
.Pp
The
.Fn destroy_dev
function takes the returned
.Fa cdev
from
.Fn make_dev
and destroys the registration for that device.
The notification is sent to
.Xr devctl 4
about the destruction event.
Do not call
.Fn destroy_dev
on devices that were created with
.Fn make_dev_alias .
.Pp
The
.Fn dev_depends
function establishes a parent-child relationship between two devices.
The net effect is that a
.Fn destroy_dev
of the parent device will also result in the destruction of the
child device(s),
if any exist.
A device may simultaneously be a parent and a child,
so it is possible to build a complete hierarchy.
.Pp
The
.Fn destroy_dev_sched_cb
function schedules execution of the
.Fn destroy_dev
for the specified
.Fa cdev
in the safe context.
After
.Fn destroy_dev
is finished, and if the supplied
.Fa cb
is not NULL, the callback
.Fa cb
is called, with argument
.Fa arg .
The
.Fn destroy_dev_sched
function is the same as
.Bd -literal -offset indent
destroy_dev_sched(cdev, NULL, NULL);
.Ed .
.Pp
The
.Fn d_close
driver method cannot call
.Fn destroy_dev
directly. Doing so causes deadlock when
.Fn destroy_dev
waits for all threads to leave the driver methods.
Also, because
.Fn destroy_dev
sleeps, no non-sleepable locks may be held over the call.
The
.Fn destroy_dev_sched
family of functions overcome these issues.
.Pp
The device driver may call the
.Fn destroy_dev_drain
function to wait until all devices that have supplied
.Fa csw
as cdevsw, are destroyed. This is useful when driver knows that
.Fn destroy_dev_sched
is called for all instantiated devices, but need to postpone module
unload until
.Fn destroy_dev
is actually finished for all of them.
.Pp
.Sh SEE ALSO
.Xr devctl 4 ,
.Xr destroy_dev_drain 9 ,
.Xr dev_clone 9 ,
.Xr devfs 5
.Sh HISTORY
The
.Fn make_dev
and
.Fn destroy_dev
functions first appeared in
.Fx 4.0 .
The function
.Fn make_dev_alias
first appeared in
.Fx 4.1 .
The function
.Fn dev_depends
first appeared in
.Fx 5.0 .
The functions
.Fn make_dev_credf ,
.Fn destroy_dev_sched ,
.Fn destroy_dev_sched_cb
first appeared in
.Fx 7.0 .