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>
27 static struct kobj_map *cdev_map;
29 static DEFINE_MUTEX(chrdevs_lock);
31 static struct char_device_struct {
32 struct char_device_struct *next;
34 unsigned int baseminor;
37 struct cdev *cdev; /* will die */
38 } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
40 /* index in the above */
41 static inline int major_to_index(unsigned major)
43 return major % CHRDEV_MAJOR_HASH_SIZE;
48 void chrdev_show(struct seq_file *f, off_t offset)
50 struct char_device_struct *cd;
52 if (offset < CHRDEV_MAJOR_HASH_SIZE) {
53 mutex_lock(&chrdevs_lock);
54 for (cd = chrdevs[offset]; cd; cd = cd->next)
55 seq_printf(f, "%3d %s\n", cd->major, cd->name);
56 mutex_unlock(&chrdevs_lock);
60 #endif /* CONFIG_PROC_FS */
63 * Register a single major with a specified minor range.
65 * If major == 0 this functions will dynamically allocate a major and return
68 * If major > 0 this function will attempt to reserve the passed range of
69 * minors and will return zero on success.
71 * Returns a -ve errno on failure.
73 static struct char_device_struct *
74 __register_chrdev_region(unsigned int major, unsigned int baseminor,
75 int minorct, const char *name)
77 struct char_device_struct *cd, **cp;
81 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
83 return ERR_PTR(-ENOMEM);
85 mutex_lock(&chrdevs_lock);
89 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
90 if (chrdevs[i] == NULL)
102 cd->baseminor = baseminor;
103 cd->minorct = minorct;
104 strlcpy(cd->name, name, sizeof(cd->name));
106 i = major_to_index(major);
108 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
109 if ((*cp)->major > major ||
110 ((*cp)->major == major &&
111 (((*cp)->baseminor >= baseminor) ||
112 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
115 /* Check for overlapping minor ranges. */
116 if (*cp && (*cp)->major == major) {
117 int old_min = (*cp)->baseminor;
118 int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
119 int new_min = baseminor;
120 int new_max = baseminor + minorct - 1;
122 /* New driver overlaps from the left. */
123 if (new_max >= old_min && new_max <= old_max) {
128 /* New driver overlaps from the right. */
129 if (new_min <= old_max && new_min >= old_min) {
134 if (new_min < old_min && new_max > old_max) {
143 mutex_unlock(&chrdevs_lock);
146 mutex_unlock(&chrdevs_lock);
151 static struct char_device_struct *
152 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
154 struct char_device_struct *cd = NULL, **cp;
155 int i = major_to_index(major);
157 mutex_lock(&chrdevs_lock);
158 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
159 if ((*cp)->major == major &&
160 (*cp)->baseminor == baseminor &&
161 (*cp)->minorct == minorct)
167 mutex_unlock(&chrdevs_lock);
172 * register_chrdev_region() - register a range of device numbers
173 * @from: the first in the desired range of device numbers; must include
175 * @count: the number of consecutive device numbers required
176 * @name: the name of the device or driver.
178 * Return value is zero on success, a negative error code on failure.
180 int register_chrdev_region(dev_t from, unsigned count, const char *name)
182 struct char_device_struct *cd;
183 dev_t to = from + count;
186 for (n = from; n < to; n = next) {
187 next = MKDEV(MAJOR(n)+1, 0);
190 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
198 for (n = from; n < to; n = next) {
199 next = MKDEV(MAJOR(n)+1, 0);
200 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
206 * alloc_chrdev_region() - register a range of char device numbers
207 * @dev: output parameter for first assigned number
208 * @baseminor: first of the requested range of minor numbers
209 * @count: the number of minor numbers required
210 * @name: the name of the associated device or driver
212 * Allocates a range of char device numbers. The major number will be
213 * chosen dynamically, and returned (along with the first minor number)
214 * in @dev. Returns zero or a negative error code.
216 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
219 struct char_device_struct *cd;
220 cd = __register_chrdev_region(0, baseminor, count, name);
223 *dev = MKDEV(cd->major, cd->baseminor);
228 * __register_chrdev() - create and register a cdev occupying a range of minors
229 * @major: major device number or 0 for dynamic allocation
230 * @baseminor: first of the requested range of minor numbers
231 * @count: the number of minor numbers required
232 * @name: name of this range of devices
233 * @fops: file operations associated with this devices
235 * If @major == 0 this functions will dynamically allocate a major and return
238 * If @major > 0 this function will attempt to reserve a device with the given
239 * major number and will return zero on success.
241 * Returns a -ve errno on failure.
243 * The name of this device has nothing to do with the name of the device in
244 * /dev. It only helps to keep track of the different owners of devices. If
245 * your module name has only one type of devices it's ok to use e.g. the name
246 * of the module here.
248 int __register_chrdev(unsigned int major, unsigned int baseminor,
249 unsigned int count, const char *name,
250 const struct file_operations *fops)
252 struct char_device_struct *cd;
256 cd = __register_chrdev_region(major, baseminor, count, name);
264 cdev->owner = fops->owner;
266 kobject_set_name(&cdev->kobj, "%s", name);
268 err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
274 return major ? 0 : cd->major;
276 kobject_put(&cdev->kobj);
278 kfree(__unregister_chrdev_region(cd->major, baseminor, count));
283 * unregister_chrdev_region() - unregister a range of device numbers
284 * @from: the first in the range of numbers to unregister
285 * @count: the number of device numbers to unregister
287 * This function will unregister a range of @count device numbers,
288 * starting with @from. The caller should normally be the one who
289 * allocated those numbers in the first place...
291 void unregister_chrdev_region(dev_t from, unsigned count)
293 dev_t to = from + count;
296 for (n = from; n < to; n = next) {
297 next = MKDEV(MAJOR(n)+1, 0);
300 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
305 * __unregister_chrdev - unregister and destroy a cdev
306 * @major: major device number
307 * @baseminor: first of the range of minor numbers
308 * @count: the number of minor numbers this cdev is occupying
309 * @name: name of this range of devices
311 * Unregister and destroy the cdev occupying the region described by
312 * @major, @baseminor and @count. This function undoes what
313 * __register_chrdev() did.
315 void __unregister_chrdev(unsigned int major, unsigned int baseminor,
316 unsigned int count, const char *name)
318 struct char_device_struct *cd;
320 cd = __unregister_chrdev_region(major, baseminor, count);
326 static DEFINE_SPINLOCK(cdev_lock);
328 static struct kobject *cdev_get(struct cdev *p)
330 struct module *owner = p->owner;
331 struct kobject *kobj;
333 if (owner && !try_module_get(owner))
335 kobj = kobject_get(&p->kobj);
341 void cdev_put(struct cdev *p)
344 struct module *owner = p->owner;
345 kobject_put(&p->kobj);
351 * Called every time a character special file is opened
353 static int chrdev_open(struct inode *inode, struct file *filp)
355 const struct file_operations *fops;
357 struct cdev *new = NULL;
360 spin_lock(&cdev_lock);
363 struct kobject *kobj;
365 spin_unlock(&cdev_lock);
366 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
369 new = container_of(kobj, struct cdev, kobj);
370 spin_lock(&cdev_lock);
371 /* Check i_cdev again in case somebody beat us to it while
372 we dropped the lock. */
375 inode->i_cdev = p = new;
376 list_add(&inode->i_devices, &p->list);
378 } else if (!cdev_get(p))
380 } else if (!cdev_get(p))
382 spin_unlock(&cdev_lock);
388 fops = fops_get(p->ops);
392 replace_fops(filp, fops);
393 if (filp->f_op->open) {
394 ret = filp->f_op->open(inode, filp);
406 void cd_forget(struct inode *inode)
408 spin_lock(&cdev_lock);
409 list_del_init(&inode->i_devices);
410 inode->i_cdev = NULL;
411 spin_unlock(&cdev_lock);
414 static void cdev_purge(struct cdev *cdev)
416 spin_lock(&cdev_lock);
417 while (!list_empty(&cdev->list)) {
419 inode = container_of(cdev->list.next, struct inode, i_devices);
420 list_del_init(&inode->i_devices);
421 inode->i_cdev = NULL;
423 spin_unlock(&cdev_lock);
427 * Dummy default file-operations: the only thing this does
428 * is contain the open that then fills in the correct operations
429 * depending on the special file...
431 const struct file_operations def_chr_fops = {
433 .llseek = noop_llseek,
436 static struct kobject *exact_match(dev_t dev, int *part, void *data)
438 struct cdev *p = data;
442 static int exact_lock(dev_t dev, void *data)
444 struct cdev *p = data;
445 return cdev_get(p) ? 0 : -1;
449 * cdev_add() - add a char device to the system
450 * @p: the cdev structure for the device
451 * @dev: the first device number for which this device is responsible
452 * @count: the number of consecutive minor numbers corresponding to this
455 * cdev_add() adds the device represented by @p to the system, making it
456 * live immediately. A negative error code is returned on failure.
458 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
465 error = kobj_map(cdev_map, dev, count, NULL,
466 exact_match, exact_lock, p);
470 kobject_get(p->kobj.parent);
475 static void cdev_unmap(dev_t dev, unsigned count)
477 kobj_unmap(cdev_map, dev, count);
481 * cdev_del() - remove a cdev from the system
482 * @p: the cdev structure to be removed
484 * cdev_del() removes @p from the system, possibly freeing the structure
487 void cdev_del(struct cdev *p)
489 cdev_unmap(p->dev, p->count);
490 kobject_put(&p->kobj);
494 static void cdev_default_release(struct kobject *kobj)
496 struct cdev *p = container_of(kobj, struct cdev, kobj);
497 struct kobject *parent = kobj->parent;
503 static void cdev_dynamic_release(struct kobject *kobj)
505 struct cdev *p = container_of(kobj, struct cdev, kobj);
506 struct kobject *parent = kobj->parent;
513 static struct kobj_type ktype_cdev_default = {
514 .release = cdev_default_release,
517 static struct kobj_type ktype_cdev_dynamic = {
518 .release = cdev_dynamic_release,
522 * cdev_alloc() - allocate a cdev structure
524 * Allocates and returns a cdev structure, or NULL on failure.
526 struct cdev *cdev_alloc(void)
528 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
530 INIT_LIST_HEAD(&p->list);
531 kobject_init(&p->kobj, &ktype_cdev_dynamic);
537 * cdev_init() - initialize a cdev structure
538 * @cdev: the structure to initialize
539 * @fops: the file_operations for this device
541 * Initializes @cdev, remembering @fops, making it ready to add to the
542 * system with cdev_add().
544 void cdev_init(struct cdev *cdev, const struct file_operations *fops)
546 memset(cdev, 0, sizeof *cdev);
547 INIT_LIST_HEAD(&cdev->list);
548 kobject_init(&cdev->kobj, &ktype_cdev_default);
552 static struct kobject *base_probe(dev_t dev, int *part, void *data)
554 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
555 /* Make old-style 2.4 aliases work */
556 request_module("char-major-%d", MAJOR(dev));
560 void __init chrdev_init(void)
562 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
566 /* Let modules do char dev stuff */
567 EXPORT_SYMBOL(register_chrdev_region);
568 EXPORT_SYMBOL(unregister_chrdev_region);
569 EXPORT_SYMBOL(alloc_chrdev_region);
570 EXPORT_SYMBOL(cdev_init);
571 EXPORT_SYMBOL(cdev_alloc);
572 EXPORT_SYMBOL(cdev_del);
573 EXPORT_SYMBOL(cdev_add);
574 EXPORT_SYMBOL(__register_chrdev);
575 EXPORT_SYMBOL(__unregister_chrdev);