The make_dev function creates a cdev structure for a new device. If DEVFS is available, it is also notified of the presence of the new device. The device will be owned by uid, with the group ownership as gid, and with the name as specified in name. 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 */
#define S_ISTXT 0001000
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 destroy_dev function takes the returned cdev from make_dev and destroys the registration for that device. 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.