make_dev.9freebsd

Langue: en

Autres versions - même langue

Version: 365197 (ubuntu - 25/10/10)

Section: 9 (Appels noyau Linux)


BSD mandoc

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 Vt cdev Ns 's and DEVFS registration for devices

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

DESCRIPTION

The Fn make_dev_credf function creates a Fa 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 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 Fa si_cred member of the initialized Fa struct cdev . The flags argument alters the operation of Fn make_dev_credf . The following values are currently accepted:

 MAKEDEV_REF     reference the created device
 

The dev_clone9 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_lookup9 drops his reference to cdev.

The Fn make_dev_cred function is equivalent to the call

 make_dev_credf(0, cdevsw, unit, cr, uid, gid, perms, fmt, ...);
 

The Fn make_dev function call is the same as

 make_dev_credf(0, cdevsw, unit, NULL, uid, gid, perms, fmt, ...);
 

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 .

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 .

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 devctl(4) about the destruction event. Do not call Fn destroy_dev on devices that were created with Fn make_dev_alias .

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.

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

 destroy_dev_sched(cdev, NULL, NULL);
 

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.

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.

SEE ALSO

devctl(4), destroy_dev_drain9, dev_clone9, devfs(5)

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 .