NAME
make_dev, make_dev_cred, make_dev_credf, make_dev_alias, destroy_dev,
destroy_dev_sched, destroy_dev_sched_cb, destroy_dev_drain, dev_depends -
manage cdev’s and DEVFS registration for devices
SYNOPSIS
#include <sys/param.h>
#include <sys/conf.h>
struct cdev *
make_dev(struct cdevsw *cdevsw, int unit, uid_t uid, gid_t gid,
int perms, const char *fmt, ...);
struct cdev *
make_dev_cred(struct cdevsw *cdevsw, int unit, struct ucred *cr,
uid_t uid, gid_t gid, int perms, const char *fmt, ...);
struct cdev *
make_dev_credf(int flags, struct cdevsw *cdevsw, int unit,
struct ucred *cr, uid_t uid, gid_t gid, int perms,
const char *fmt, ...);
struct cdev *
make_dev_alias(struct cdev *pdev, const char *fmt, ...);
void
destroy_dev(struct cdev *dev);
void
destroy_dev_sched(struct cdev *dev);
void
destroy_dev_sched_cb(struct cdev *dev, void (*cb)(void *), void *arg);
void
destroy_dev_drain(struct cdevsw *csw);
void
dev_depends(struct cdev *pdev, struct cdev *cdev);
DESCRIPTION
The make_dev_credf() function creates a cdev structure for a new device.
It also notifies devfs(5) of the presence of the new device, that causes
corresponding nodes to be created. Besides this, a devctl(4)
notification is sent. The device will be owned by uid, with the group
ownership as gid. The name is the expansion of fmt and following
arguments as printf(9) would print it. The name determines its path
under /dev or other devfs(5) mount point and may contain slash ‘/’
characters to denote subdirectories. The permissions of the file
specified in perms are defined in
#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
The cr argument specifies credentials that will be stored in the si_cred
member of the initialized struct cdev. The flags argument alters the
operation of make_dev_credf(). The following values are currently
accepted:
MAKEDEV_REF reference the created device
The dev_clone(9) event handler shall specify MAKEDEV_REF flag when
creating a device in response to lookup, to avoid race where the device
created is destroyed immediately after devfs_lookup(9) drops his
reference to cdev.
The make_dev_cred() function is equivalent to the call
make_dev_credf(0, cdevsw, unit, cr, uid, gid, perms, fmt, ...);
The make_dev() function call is the same as
make_dev_credf(0, cdevsw, unit, NULL, uid, gid, perms, fmt, ...);
The make_dev_alias() function takes the returned cdev from make_dev() and
makes another (aliased) name for this device. It is an error to call
make_dev_alias() prior to calling make_dev().
The cdev returned by make_dev() and make_dev_alias() has two fields,
si_drv1 and si_drv2, that are available to store state. Both fields are
of type void *. These are designed to replace the unit argument to
make_dev(), which can be obtained with dev2unit().
The destroy_dev() function takes the returned cdev from make_dev() and
destroys the registration for that device. The notification is sent to
devctl(4) about the destruction event. Do not call destroy_dev() on
devices that were created with make_dev_alias().
The dev_depends() function establishes a parent-child relationship
between two devices. The net effect is that a 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.
The destroy_dev_sched_cb() function schedules execution of the
destroy_dev() for the specified cdev in the safe context. After
destroy_dev() is finished, and if the supplied cb is not NULL, the
callback cb is called, with argument arg. The destroy_dev_sched()
function is the same as
destroy_dev_sched(cdev, NULL, NULL);
The d_close() driver method cannot call destroy_dev() directly. Doing so
causes deadlock when destroy_dev() waits for all threads to leave the
driver methods. Also, because destroy_dev() sleeps, no non-sleepable
locks may be held over the call. The destroy_dev_sched() family of
functions overcome these issues.
The device driver may call the destroy_dev_drain() function to wait until
all devices that have supplied csw as cdevsw, are destroyed. This is
useful when driver knows that destroy_dev_sched() is called for all
instantiated devices, but need to postpone module unload until
destroy_dev() is actually finished for all of them.
SEE ALSO
devctl(4), destroy_dev_drain(9), dev_clone(9), devfs(5)
HISTORY
The make_dev() and destroy_dev() functions first appeared in FreeBSD 4.0.
The function make_dev_alias() first appeared in FreeBSD 4.1. The
function dev_depends() first appeared in FreeBSD 5.0. The functions
make_dev_credf(), destroy_dev_sched(), destroy_dev_sched_cb() first
appeared in FreeBSD 7.0.