Provided by: freebsd-manpages_9.2+1-1_all 
NAME
make_dev, make_dev_cred, make_dev_credf, make_dev_p, make_dev_alias, make_dev_alias_p,
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, ...);
int
make_dev_p(int flags, struct cdev **cdev, struct cdevsw *devsw, struct ucred *cr, uid_t uid,
gid_t gid, int mode, const char *fmt, ...);
struct cdev *
make_dev_alias(struct cdev *pdev, const char *fmt, ...);
int
make_dev_alias_p(int flags, struct cdev **cdev, 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 <sys/stat.h>:
#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() or
make_dev_p(). The following values are currently accepted:
MAKEDEV_REF reference the created device
MAKEDEV_NOWAIT do not sleep, the call may fail
MAKEDEV_WAITOK allow the function to sleep to satisfy malloc
MAKEDEV_ETERNAL created device will be never destroyed
MAKEDEV_CHECKNAME return an error if the device name is invalid or already exists
Only MAKEDEV_NOWAIT, MAKEDEV_WAITOK and MAKEDEV_CHECKNAME values are accepted for the
make_dev_alias_p() function.
The MAKEDEV_WAITOK flag is assumed if none of MAKEDEV_WAITOK, MAKEDEV_NOWAIT is specified.
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 MAKEDEV_ETERNAL flag allows the kernel to not acquire some locks when translating system
calls into the cdevsw methods calls. It is responsibility of the driver author to make sure
that destroy_dev() is never called on the returned cdev. For the convenience, use the
MAKEDEV_ETERNAL_KLD flag for the code that can be compiled into kernel or loaded (and
unloaded) as loadable module.
A panic will occur if the MAKEDEV_CHECKNAME flag is not specified and the device name is
invalid or already exists.
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_p() function is similar to make_dev_credf() but it may return an error number
and takes a pointer to the resulting *cdev as an argument.
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().
make_dev_alias_p() function is similar to make_dev_alias() but it takes a pointer to the
resulting *cdev as an argument and may return an error.
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_cb(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.
RETURN VALUES
If successful, make_dev_p() will return 0, otherwise it will return an error. If
successful, make_dev_credf() will return a valid cdev pointer, otherwise it will return
NULL.
ERRORS
The make_dev_p() and make_dev_alias_p() call will fail and the device will be not registered
if:
[ENOMEM] The MAKEDEV_NOWAIT flag was specified and a memory allocation request
could not be satisfied.
[ENAMETOOLONG] The MAKEDEV_CHECKNAME flag was specified and the provided device name is
longer than SPECNAMELEN.
[EINVAL] The MAKEDEV_CHECKNAME flag was specified and the provided device name is
empty, contains a "." or ".." path component or ends with ‘/’.
[EEXIST] The MAKEDEV_CHECKNAME flag was specified and the provided device name
already exists.
SEE ALSO
devctl(4), devfs(5), destroy_dev_drain(9), dev_clone(9)
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. The function make_dev_p() first appeared in FreeBSD 8.2.