4 * Copyright (C) 1991, 1992 Linus Torvalds
7 #include <linux/init.h>
9 #include <linux/kdev_t.h>
10 #include <linux/slab.h>
11 #include <linux/string.h>
13 #include <linux/major.h>
14 #include <linux/errno.h>
15 #include <linux/module.h>
16 #include <linux/seq_file.h>
18 #include <linux/kobject.h>
19 #include <linux/kobj_map.h>
20 #include <linux/cdev.h>
21 #include <linux/mutex.h>
22 #include <linux/backing-dev.h>
23 #include <linux/tty.h>
28 * capabilities for /dev/mem, /dev/kmem and similar directly mappable character
30 * - permits shared-mmap for read, write and/or exec
31 * - does not permit private mmap in NOMMU mode (can't do COW)
32 * - no readahead or I/O queue unplugging required
34 struct backing_dev_info directly_mappable_cdev_bdi = {
38 /* permit private copies of the data to be taken */
41 /* permit direct mmap, for read, write or exec */
43 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP |
44 /* no writeback happens */
45 BDI_CAP_NO_ACCT_AND_WRITEBACK),
48 static struct kobj_map *cdev_map;
50 static DEFINE_MUTEX(chrdevs_lock);
52 static struct char_device_struct {
53 struct char_device_struct *next;
55 unsigned int baseminor;
58 struct cdev *cdev; /* will die */
59 } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
61 /* index in the above */
62 static inline int major_to_index(unsigned major)
64 return major % CHRDEV_MAJOR_HASH_SIZE;
69 void chrdev_show(struct seq_file *f, off_t offset)
71 struct char_device_struct *cd;
73 if (offset < CHRDEV_MAJOR_HASH_SIZE) {
74 mutex_lock(&chrdevs_lock);
75 for (cd = chrdevs[offset]; cd; cd = cd->next)
76 seq_printf(f, "%3d %s\n", cd->major, cd->name);
77 mutex_unlock(&chrdevs_lock);
81 #endif /* CONFIG_PROC_FS */
84 * Register a single major with a specified minor range.
86 * If major == 0 this functions will dynamically allocate a major and return
89 * If major > 0 this function will attempt to reserve the passed range of
90 * minors and will return zero on success.
92 * Returns a -ve errno on failure.
94 static struct char_device_struct *
95 __register_chrdev_region(unsigned int major, unsigned int baseminor,
96 int minorct, const char *name)
98 struct char_device_struct *cd, **cp;
102 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
104 return ERR_PTR(-ENOMEM);
106 mutex_lock(&chrdevs_lock);
110 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
111 if (chrdevs[i] == NULL)
124 cd->baseminor = baseminor;
125 cd->minorct = minorct;
126 strlcpy(cd->name, name, sizeof(cd->name));
128 i = major_to_index(major);
130 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
131 if ((*cp)->major > major ||
132 ((*cp)->major == major &&
133 (((*cp)->baseminor >= baseminor) ||
134 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
137 /* Check for overlapping minor ranges. */
138 if (*cp && (*cp)->major == major) {
139 int old_min = (*cp)->baseminor;
140 int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
141 int new_min = baseminor;
142 int new_max = baseminor + minorct - 1;
144 /* New driver overlaps from the left. */
145 if (new_max >= old_min && new_max <= old_max) {
150 /* New driver overlaps from the right. */
151 if (new_min <= old_max && new_min >= old_min) {
159 mutex_unlock(&chrdevs_lock);
162 mutex_unlock(&chrdevs_lock);
167 static struct char_device_struct *
168 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
170 struct char_device_struct *cd = NULL, **cp;
171 int i = major_to_index(major);
173 mutex_lock(&chrdevs_lock);
174 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
175 if ((*cp)->major == major &&
176 (*cp)->baseminor == baseminor &&
177 (*cp)->minorct == minorct)
183 mutex_unlock(&chrdevs_lock);
188 * register_chrdev_region() - register a range of device numbers
189 * @from: the first in the desired range of device numbers; must include
191 * @count: the number of consecutive device numbers required
192 * @name: the name of the device or driver.
194 * Return value is zero on success, a negative error code on failure.
196 int register_chrdev_region(dev_t from, unsigned count, const char *name)
198 struct char_device_struct *cd;
199 dev_t to = from + count;
202 for (n = from; n < to; n = next) {
203 next = MKDEV(MAJOR(n)+1, 0);
206 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
214 for (n = from; n < to; n = next) {
215 next = MKDEV(MAJOR(n)+1, 0);
216 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
222 * alloc_chrdev_region() - register a range of char device numbers
223 * @dev: output parameter for first assigned number
224 * @baseminor: first of the requested range of minor numbers
225 * @count: the number of minor numbers required
226 * @name: the name of the associated device or driver
228 * Allocates a range of char device numbers. The major number will be
229 * chosen dynamically, and returned (along with the first minor number)
230 * in @dev. Returns zero or a negative error code.
232 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
235 struct char_device_struct *cd;
236 cd = __register_chrdev_region(0, baseminor, count, name);
239 *dev = MKDEV(cd->major, cd->baseminor);
244 * __register_chrdev() - create and register a cdev occupying a range of minors
245 * @major: major device number or 0 for dynamic allocation
246 * @baseminor: first of the requested range of minor numbers
247 * @count: the number of minor numbers required
248 * @name: name of this range of devices
249 * @fops: file operations associated with this devices
251 * If @major == 0 this functions will dynamically allocate a major and return
254 * If @major > 0 this function will attempt to reserve a device with the given
255 * major number and will return zero on success.
257 * Returns a -ve errno on failure.
259 * The name of this device has nothing to do with the name of the device in
260 * /dev. It only helps to keep track of the different owners of devices. If
261 * your module name has only one type of devices it's ok to use e.g. the name
262 * of the module here.
264 int __register_chrdev(unsigned int major, unsigned int baseminor,
265 unsigned int count, const char *name,
266 const struct file_operations *fops)
268 struct char_device_struct *cd;
272 cd = __register_chrdev_region(major, baseminor, count, name);
280 cdev->owner = fops->owner;
282 kobject_set_name(&cdev->kobj, "%s", name);
284 err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
290 return major ? 0 : cd->major;
292 kobject_put(&cdev->kobj);
294 kfree(__unregister_chrdev_region(cd->major, baseminor, count));
299 * unregister_chrdev_region() - return a range of device numbers
300 * @from: the first in the range of numbers to unregister
301 * @count: the number of device numbers to unregister
303 * This function will unregister a range of @count device numbers,
304 * starting with @from. The caller should normally be the one who
305 * allocated those numbers in the first place...
307 void unregister_chrdev_region(dev_t from, unsigned count)
309 dev_t to = from + count;
312 for (n = from; n < to; n = next) {
313 next = MKDEV(MAJOR(n)+1, 0);
316 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
321 * __unregister_chrdev - unregister and destroy a cdev
322 * @major: major device number
323 * @baseminor: first of the range of minor numbers
324 * @count: the number of minor numbers this cdev is occupying
325 * @name: name of this range of devices
327 * Unregister and destroy the cdev occupying the region described by
328 * @major, @baseminor and @count. This function undoes what
329 * __register_chrdev() did.
331 void __unregister_chrdev(unsigned int major, unsigned int baseminor,
332 unsigned int count, const char *name)
334 struct char_device_struct *cd;
336 cd = __unregister_chrdev_region(major, baseminor, count);
342 static DEFINE_SPINLOCK(cdev_lock);
344 static struct kobject *cdev_get(struct cdev *p)
346 struct module *owner = p->owner;
347 struct kobject *kobj;
349 if (owner && !try_module_get(owner))
351 kobj = kobject_get(&p->kobj);
357 void cdev_put(struct cdev *p)
360 struct module *owner = p->owner;
361 kobject_put(&p->kobj);
367 * Called every time a character special file is opened
369 static int chrdev_open(struct inode *inode, struct file *filp)
372 struct cdev *new = NULL;
375 spin_lock(&cdev_lock);
378 struct kobject *kobj;
380 spin_unlock(&cdev_lock);
381 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
384 new = container_of(kobj, struct cdev, kobj);
385 spin_lock(&cdev_lock);
386 /* Check i_cdev again in case somebody beat us to it while
387 we dropped the lock. */
390 inode->i_cdev = p = new;
391 list_add(&inode->i_devices, &p->list);
393 } else if (!cdev_get(p))
395 } else if (!cdev_get(p))
397 spin_unlock(&cdev_lock);
403 filp->f_op = fops_get(p->ops);
407 if (filp->f_op->open) {
408 ret = filp->f_op->open(inode,filp);
420 void cd_forget(struct inode *inode)
422 spin_lock(&cdev_lock);
423 list_del_init(&inode->i_devices);
424 inode->i_cdev = NULL;
425 spin_unlock(&cdev_lock);
428 static void cdev_purge(struct cdev *cdev)
430 spin_lock(&cdev_lock);
431 while (!list_empty(&cdev->list)) {
433 inode = container_of(cdev->list.next, struct inode, i_devices);
434 list_del_init(&inode->i_devices);
435 inode->i_cdev = NULL;
437 spin_unlock(&cdev_lock);
441 * Dummy default file-operations: the only thing this does
442 * is contain the open that then fills in the correct operations
443 * depending on the special file...
445 const struct file_operations def_chr_fops = {
447 .llseek = noop_llseek,
450 static struct kobject *exact_match(dev_t dev, int *part, void *data)
452 struct cdev *p = data;
456 static int exact_lock(dev_t dev, void *data)
458 struct cdev *p = data;
459 return cdev_get(p) ? 0 : -1;
463 * cdev_add() - add a char device to the system
464 * @p: the cdev structure for the device
465 * @dev: the first device number for which this device is responsible
466 * @count: the number of consecutive minor numbers corresponding to this
469 * cdev_add() adds the device represented by @p to the system, making it
470 * live immediately. A negative error code is returned on failure.
472 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
476 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
479 static void cdev_unmap(dev_t dev, unsigned count)
481 kobj_unmap(cdev_map, dev, count);
485 * cdev_del() - remove a cdev from the system
486 * @p: the cdev structure to be removed
488 * cdev_del() removes @p from the system, possibly freeing the structure
491 void cdev_del(struct cdev *p)
493 cdev_unmap(p->dev, p->count);
494 kobject_put(&p->kobj);
498 static void cdev_default_release(struct kobject *kobj)
500 struct cdev *p = container_of(kobj, struct cdev, kobj);
504 static void cdev_dynamic_release(struct kobject *kobj)
506 struct cdev *p = container_of(kobj, struct cdev, kobj);
511 static struct kobj_type ktype_cdev_default = {
512 .release = cdev_default_release,
515 static struct kobj_type ktype_cdev_dynamic = {
516 .release = cdev_dynamic_release,
520 * cdev_alloc() - allocate a cdev structure
522 * Allocates and returns a cdev structure, or NULL on failure.
524 struct cdev *cdev_alloc(void)
526 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
528 INIT_LIST_HEAD(&p->list);
529 kobject_init(&p->kobj, &ktype_cdev_dynamic);
535 * cdev_init() - initialize a cdev structure
536 * @cdev: the structure to initialize
537 * @fops: the file_operations for this device
539 * Initializes @cdev, remembering @fops, making it ready to add to the
540 * system with cdev_add().
542 void cdev_init(struct cdev *cdev, const struct file_operations *fops)
544 memset(cdev, 0, sizeof *cdev);
545 INIT_LIST_HEAD(&cdev->list);
546 kobject_init(&cdev->kobj, &ktype_cdev_default);
550 static struct kobject *base_probe(dev_t dev, int *part, void *data)
552 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
553 /* Make old-style 2.4 aliases work */
554 request_module("char-major-%d", MAJOR(dev));
558 void __init chrdev_init(void)
560 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
561 bdi_init(&directly_mappable_cdev_bdi);
565 /* Let modules do char dev stuff */
566 EXPORT_SYMBOL(register_chrdev_region);
567 EXPORT_SYMBOL(unregister_chrdev_region);
568 EXPORT_SYMBOL(alloc_chrdev_region);
569 EXPORT_SYMBOL(cdev_init);
570 EXPORT_SYMBOL(cdev_alloc);
571 EXPORT_SYMBOL(cdev_del);
572 EXPORT_SYMBOL(cdev_add);
573 EXPORT_SYMBOL(__register_chrdev);
574 EXPORT_SYMBOL(__unregister_chrdev);
575 EXPORT_SYMBOL(directly_mappable_cdev_bdi);