blob: 1f3285affa39c9d06da9fb3af7bee91094d894f9 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/char_dev.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
Linus Torvalds1da177e2005-04-16 15:20:36 -07007#include <linux/init.h>
8#include <linux/fs.h>
9#include <linux/slab.h>
10#include <linux/string.h>
11
12#include <linux/major.h>
13#include <linux/errno.h>
14#include <linux/module.h>
15#include <linux/smp_lock.h>
Joe Korty68eef3b2006-03-31 02:30:32 -080016#include <linux/seq_file.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
18#include <linux/kobject.h>
19#include <linux/kobj_map.h>
20#include <linux/cdev.h>
Jes Sorensen58383af2006-02-06 14:12:43 -080021#include <linux/mutex.h>
David Howells5da61852006-09-27 01:50:16 -070022#include <linux/backing-dev.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023
24#ifdef CONFIG_KMOD
25#include <linux/kmod.h>
26#endif
27
David Howells5da61852006-09-27 01:50:16 -070028/*
29 * capabilities for /dev/mem, /dev/kmem and similar directly mappable character
30 * devices
31 * - permits shared-mmap for read, write and/or exec
32 * - does not permit private mmap in NOMMU mode (can't do COW)
33 * - no readahead or I/O queue unplugging required
34 */
35struct backing_dev_info directly_mappable_cdev_bdi = {
36 .capabilities = (
37#ifdef CONFIG_MMU
38 /* permit private copies of the data to be taken */
39 BDI_CAP_MAP_COPY |
40#endif
41 /* permit direct mmap, for read, write or exec */
42 BDI_CAP_MAP_DIRECT |
43 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),
44};
45
Linus Torvalds1da177e2005-04-16 15:20:36 -070046static struct kobj_map *cdev_map;
47
Jes Sorensen58383af2006-02-06 14:12:43 -080048static DEFINE_MUTEX(chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070049
50static struct char_device_struct {
51 struct char_device_struct *next;
52 unsigned int major;
53 unsigned int baseminor;
54 int minorct;
Neil Horman7170be52006-01-14 13:20:38 -080055 char name[64];
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 struct file_operations *fops;
57 struct cdev *cdev; /* will die */
Joe Korty68eef3b2006-03-31 02:30:32 -080058} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -070059
60/* index in the above */
61static inline int major_to_index(int major)
62{
Joe Korty68eef3b2006-03-31 02:30:32 -080063 return major % CHRDEV_MAJOR_HASH_SIZE;
Linus Torvalds1da177e2005-04-16 15:20:36 -070064}
65
Joe Korty68eef3b2006-03-31 02:30:32 -080066#ifdef CONFIG_PROC_FS
Neil Horman7170be52006-01-14 13:20:38 -080067
Joe Korty68eef3b2006-03-31 02:30:32 -080068void chrdev_show(struct seq_file *f, off_t offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -070069{
70 struct char_device_struct *cd;
Linus Torvalds1da177e2005-04-16 15:20:36 -070071
Joe Korty68eef3b2006-03-31 02:30:32 -080072 if (offset < CHRDEV_MAJOR_HASH_SIZE) {
73 mutex_lock(&chrdevs_lock);
74 for (cd = chrdevs[offset]; cd; cd = cd->next)
75 seq_printf(f, "%3d %s\n", cd->major, cd->name);
76 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 }
Neil Horman7170be52006-01-14 13:20:38 -080078}
79
Joe Korty68eef3b2006-03-31 02:30:32 -080080#endif /* CONFIG_PROC_FS */
Linus Torvalds1da177e2005-04-16 15:20:36 -070081
82/*
83 * Register a single major with a specified minor range.
84 *
85 * If major == 0 this functions will dynamically allocate a major and return
86 * its number.
87 *
88 * If major > 0 this function will attempt to reserve the passed range of
89 * minors and will return zero on success.
90 *
91 * Returns a -ve errno on failure.
92 */
93static struct char_device_struct *
94__register_chrdev_region(unsigned int major, unsigned int baseminor,
95 int minorct, const char *name)
96{
97 struct char_device_struct *cd, **cp;
98 int ret = 0;
99 int i;
100
Oliver Neukum11b0b5a2006-03-25 03:08:13 -0800101 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 if (cd == NULL)
103 return ERR_PTR(-ENOMEM);
104
Jes Sorensen58383af2006-02-06 14:12:43 -0800105 mutex_lock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106
107 /* temporary */
108 if (major == 0) {
109 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
110 if (chrdevs[i] == NULL)
111 break;
112 }
113
114 if (i == 0) {
115 ret = -EBUSY;
116 goto out;
117 }
118 major = i;
119 ret = major;
120 }
121
122 cd->major = major;
123 cd->baseminor = baseminor;
124 cd->minorct = minorct;
Neil Horman7170be52006-01-14 13:20:38 -0800125 strncpy(cd->name,name, 64);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126
127 i = major_to_index(major);
128
129 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
130 if ((*cp)->major > major ||
Amos Waterland01d553d2006-09-29 02:00:08 -0700131 ((*cp)->major == major &&
132 (((*cp)->baseminor >= baseminor) ||
133 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134 break;
Amos Waterland01d553d2006-09-29 02:00:08 -0700135
136 /* Check for overlapping minor ranges. */
137 if (*cp && (*cp)->major == major) {
138 int old_min = (*cp)->baseminor;
139 int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
140 int new_min = baseminor;
141 int new_max = baseminor + minorct - 1;
142
143 /* New driver overlaps from the left. */
144 if (new_max >= old_min && new_max <= old_max) {
145 ret = -EBUSY;
146 goto out;
147 }
148
149 /* New driver overlaps from the right. */
150 if (new_min <= old_max && new_min >= old_min) {
151 ret = -EBUSY;
152 goto out;
153 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 }
Amos Waterland01d553d2006-09-29 02:00:08 -0700155
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 cd->next = *cp;
157 *cp = cd;
Jes Sorensen58383af2006-02-06 14:12:43 -0800158 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 return cd;
160out:
Jes Sorensen58383af2006-02-06 14:12:43 -0800161 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 kfree(cd);
163 return ERR_PTR(ret);
164}
165
166static struct char_device_struct *
167__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
168{
169 struct char_device_struct *cd = NULL, **cp;
170 int i = major_to_index(major);
171
Jes Sorensen58383af2006-02-06 14:12:43 -0800172 mutex_lock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
174 if ((*cp)->major == major &&
175 (*cp)->baseminor == baseminor &&
176 (*cp)->minorct == minorct)
177 break;
178 if (*cp) {
179 cd = *cp;
180 *cp = cd->next;
181 }
Jes Sorensen58383af2006-02-06 14:12:43 -0800182 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 return cd;
184}
185
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700186/**
187 * register_chrdev_region() - register a range of device numbers
188 * @from: the first in the desired range of device numbers; must include
189 * the major number.
190 * @count: the number of consecutive device numbers required
191 * @name: the name of the device or driver.
192 *
193 * Return value is zero on success, a negative error code on failure.
194 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195int register_chrdev_region(dev_t from, unsigned count, const char *name)
196{
197 struct char_device_struct *cd;
198 dev_t to = from + count;
199 dev_t n, next;
200
201 for (n = from; n < to; n = next) {
202 next = MKDEV(MAJOR(n)+1, 0);
203 if (next > to)
204 next = to;
205 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
206 next - n, name);
207 if (IS_ERR(cd))
208 goto fail;
209 }
210 return 0;
211fail:
212 to = n;
213 for (n = from; n < to; n = next) {
214 next = MKDEV(MAJOR(n)+1, 0);
215 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
216 }
217 return PTR_ERR(cd);
218}
219
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700220/**
221 * alloc_chrdev_region() - register a range of char device numbers
222 * @dev: output parameter for first assigned number
223 * @baseminor: first of the requested range of minor numbers
224 * @count: the number of minor numbers required
225 * @name: the name of the associated device or driver
226 *
227 * Allocates a range of char device numbers. The major number will be
228 * chosen dynamically, and returned (along with the first minor number)
229 * in @dev. Returns zero or a negative error code.
230 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
232 const char *name)
233{
234 struct char_device_struct *cd;
235 cd = __register_chrdev_region(0, baseminor, count, name);
236 if (IS_ERR(cd))
237 return PTR_ERR(cd);
238 *dev = MKDEV(cd->major, cd->baseminor);
239 return 0;
240}
241
Rolf Eike Beerd247e2c2006-07-14 00:24:23 -0700242/**
243 * register_chrdev() - Register a major number for character devices.
244 * @major: major device number or 0 for dynamic allocation
245 * @name: name of this range of devices
246 * @fops: file operations associated with this devices
247 *
248 * If @major == 0 this functions will dynamically allocate a major and return
249 * its number.
250 *
251 * If @major > 0 this function will attempt to reserve a device with the given
252 * major number and will return zero on success.
253 *
254 * Returns a -ve errno on failure.
255 *
256 * The name of this device has nothing to do with the name of the device in
257 * /dev. It only helps to keep track of the different owners of devices. If
258 * your module name has only one type of devices it's ok to use e.g. the name
259 * of the module here.
260 *
261 * This function registers a range of 256 minor numbers. The first minor number
262 * is 0.
263 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700264int register_chrdev(unsigned int major, const char *name,
Arjan van de Ven99ac48f2006-03-28 01:56:41 -0800265 const struct file_operations *fops)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266{
267 struct char_device_struct *cd;
268 struct cdev *cdev;
269 char *s;
270 int err = -ENOMEM;
271
272 cd = __register_chrdev_region(major, 0, 256, name);
273 if (IS_ERR(cd))
274 return PTR_ERR(cd);
275
276 cdev = cdev_alloc();
277 if (!cdev)
278 goto out2;
279
280 cdev->owner = fops->owner;
281 cdev->ops = fops;
282 kobject_set_name(&cdev->kobj, "%s", name);
283 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
284 *s = '!';
285
286 err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
287 if (err)
288 goto out;
289
290 cd->cdev = cdev;
291
292 return major ? 0 : cd->major;
293out:
294 kobject_put(&cdev->kobj);
295out2:
296 kfree(__unregister_chrdev_region(cd->major, 0, 256));
297 return err;
298}
299
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700300/**
301 * unregister_chrdev_region() - return a range of device numbers
302 * @from: the first in the range of numbers to unregister
303 * @count: the number of device numbers to unregister
304 *
305 * This function will unregister a range of @count device numbers,
306 * starting with @from. The caller should normally be the one who
307 * allocated those numbers in the first place...
308 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309void unregister_chrdev_region(dev_t from, unsigned count)
310{
311 dev_t to = from + count;
312 dev_t n, next;
313
314 for (n = from; n < to; n = next) {
315 next = MKDEV(MAJOR(n)+1, 0);
316 if (next > to)
317 next = to;
318 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
319 }
320}
321
322int unregister_chrdev(unsigned int major, const char *name)
323{
324 struct char_device_struct *cd;
325 cd = __unregister_chrdev_region(major, 0, 256);
326 if (cd && cd->cdev)
327 cdev_del(cd->cdev);
328 kfree(cd);
329 return 0;
330}
331
332static DEFINE_SPINLOCK(cdev_lock);
333
334static struct kobject *cdev_get(struct cdev *p)
335{
336 struct module *owner = p->owner;
337 struct kobject *kobj;
338
339 if (owner && !try_module_get(owner))
340 return NULL;
341 kobj = kobject_get(&p->kobj);
342 if (!kobj)
343 module_put(owner);
344 return kobj;
345}
346
347void cdev_put(struct cdev *p)
348{
349 if (p) {
Brian King7da68442005-07-12 13:58:30 -0700350 struct module *owner = p->owner;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700351 kobject_put(&p->kobj);
Brian King7da68442005-07-12 13:58:30 -0700352 module_put(owner);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353 }
354}
355
356/*
357 * Called every time a character special file is opened
358 */
359int chrdev_open(struct inode * inode, struct file * filp)
360{
361 struct cdev *p;
362 struct cdev *new = NULL;
363 int ret = 0;
364
365 spin_lock(&cdev_lock);
366 p = inode->i_cdev;
367 if (!p) {
368 struct kobject *kobj;
369 int idx;
370 spin_unlock(&cdev_lock);
371 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
372 if (!kobj)
373 return -ENXIO;
374 new = container_of(kobj, struct cdev, kobj);
375 spin_lock(&cdev_lock);
376 p = inode->i_cdev;
377 if (!p) {
378 inode->i_cdev = p = new;
379 inode->i_cindex = idx;
380 list_add(&inode->i_devices, &p->list);
381 new = NULL;
382 } else if (!cdev_get(p))
383 ret = -ENXIO;
384 } else if (!cdev_get(p))
385 ret = -ENXIO;
386 spin_unlock(&cdev_lock);
387 cdev_put(new);
388 if (ret)
389 return ret;
390 filp->f_op = fops_get(p->ops);
391 if (!filp->f_op) {
392 cdev_put(p);
393 return -ENXIO;
394 }
395 if (filp->f_op->open) {
396 lock_kernel();
397 ret = filp->f_op->open(inode,filp);
398 unlock_kernel();
399 }
400 if (ret)
401 cdev_put(p);
402 return ret;
403}
404
405void cd_forget(struct inode *inode)
406{
407 spin_lock(&cdev_lock);
408 list_del_init(&inode->i_devices);
409 inode->i_cdev = NULL;
410 spin_unlock(&cdev_lock);
411}
412
Adrian Bunk75c96f82005-05-05 16:16:09 -0700413static void cdev_purge(struct cdev *cdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414{
415 spin_lock(&cdev_lock);
416 while (!list_empty(&cdev->list)) {
417 struct inode *inode;
418 inode = container_of(cdev->list.next, struct inode, i_devices);
419 list_del_init(&inode->i_devices);
420 inode->i_cdev = NULL;
421 }
422 spin_unlock(&cdev_lock);
423}
424
425/*
426 * Dummy default file-operations: the only thing this does
427 * is contain the open that then fills in the correct operations
428 * depending on the special file...
429 */
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -0800430const struct file_operations def_chr_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 .open = chrdev_open,
432};
433
434static struct kobject *exact_match(dev_t dev, int *part, void *data)
435{
436 struct cdev *p = data;
437 return &p->kobj;
438}
439
440static int exact_lock(dev_t dev, void *data)
441{
442 struct cdev *p = data;
443 return cdev_get(p) ? 0 : -1;
444}
445
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700446/**
447 * cdev_add() - add a char device to the system
448 * @p: the cdev structure for the device
449 * @dev: the first device number for which this device is responsible
450 * @count: the number of consecutive minor numbers corresponding to this
451 * device
452 *
453 * cdev_add() adds the device represented by @p to the system, making it
454 * live immediately. A negative error code is returned on failure.
455 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456int cdev_add(struct cdev *p, dev_t dev, unsigned count)
457{
458 p->dev = dev;
459 p->count = count;
460 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
461}
462
463static void cdev_unmap(dev_t dev, unsigned count)
464{
465 kobj_unmap(cdev_map, dev, count);
466}
467
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700468/**
469 * cdev_del() - remove a cdev from the system
470 * @p: the cdev structure to be removed
471 *
472 * cdev_del() removes @p from the system, possibly freeing the structure
473 * itself.
474 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475void cdev_del(struct cdev *p)
476{
477 cdev_unmap(p->dev, p->count);
478 kobject_put(&p->kobj);
479}
480
481
482static void cdev_default_release(struct kobject *kobj)
483{
484 struct cdev *p = container_of(kobj, struct cdev, kobj);
485 cdev_purge(p);
486}
487
488static void cdev_dynamic_release(struct kobject *kobj)
489{
490 struct cdev *p = container_of(kobj, struct cdev, kobj);
491 cdev_purge(p);
492 kfree(p);
493}
494
495static struct kobj_type ktype_cdev_default = {
496 .release = cdev_default_release,
497};
498
499static struct kobj_type ktype_cdev_dynamic = {
500 .release = cdev_dynamic_release,
501};
502
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700503/**
504 * cdev_alloc() - allocate a cdev structure
505 *
506 * Allocates and returns a cdev structure, or NULL on failure.
507 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700508struct cdev *cdev_alloc(void)
509{
Oliver Neukum11b0b5a2006-03-25 03:08:13 -0800510 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 if (p) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 p->kobj.ktype = &ktype_cdev_dynamic;
513 INIT_LIST_HEAD(&p->list);
514 kobject_init(&p->kobj);
515 }
516 return p;
517}
518
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700519/**
520 * cdev_init() - initialize a cdev structure
521 * @cdev: the structure to initialize
522 * @fops: the file_operations for this device
523 *
524 * Initializes @cdev, remembering @fops, making it ready to add to the
525 * system with cdev_add().
526 */
Arjan van de Ven99ac48f2006-03-28 01:56:41 -0800527void cdev_init(struct cdev *cdev, const struct file_operations *fops)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528{
529 memset(cdev, 0, sizeof *cdev);
530 INIT_LIST_HEAD(&cdev->list);
531 cdev->kobj.ktype = &ktype_cdev_default;
532 kobject_init(&cdev->kobj);
533 cdev->ops = fops;
534}
535
536static struct kobject *base_probe(dev_t dev, int *part, void *data)
537{
538 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
539 /* Make old-style 2.4 aliases work */
540 request_module("char-major-%d", MAJOR(dev));
541 return NULL;
542}
543
544void __init chrdev_init(void)
545{
546 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
547}
548
549
550/* Let modules do char dev stuff */
551EXPORT_SYMBOL(register_chrdev_region);
552EXPORT_SYMBOL(unregister_chrdev_region);
553EXPORT_SYMBOL(alloc_chrdev_region);
554EXPORT_SYMBOL(cdev_init);
555EXPORT_SYMBOL(cdev_alloc);
556EXPORT_SYMBOL(cdev_del);
557EXPORT_SYMBOL(cdev_add);
558EXPORT_SYMBOL(register_chrdev);
559EXPORT_SYMBOL(unregister_chrdev);
David Howells5da61852006-09-27 01:50:16 -0700560EXPORT_SYMBOL(directly_mappable_cdev_bdi);