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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>
Andrew Mortonb446b602007-02-20 13:57:48 -08009#include <linux/kdev_t.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070010#include <linux/slab.h>
11#include <linux/string.h>
12
13#include <linux/major.h>
14#include <linux/errno.h>
15#include <linux/module.h>
16#include <linux/smp_lock.h>
Joe Korty68eef3b2006-03-31 02:30:32 -080017#include <linux/seq_file.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
19#include <linux/kobject.h>
20#include <linux/kobj_map.h>
21#include <linux/cdev.h>
Jes Sorensen58383af2006-02-06 14:12:43 -080022#include <linux/mutex.h>
David Howells5da61852006-09-27 01:50:16 -070023#include <linux/backing-dev.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024
25#ifdef CONFIG_KMOD
26#include <linux/kmod.h>
27#endif
David Howells07f3f052006-09-30 20:52:18 +020028#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070029
David Howells5da61852006-09-27 01:50:16 -070030/*
31 * capabilities for /dev/mem, /dev/kmem and similar directly mappable character
32 * devices
33 * - permits shared-mmap for read, write and/or exec
34 * - does not permit private mmap in NOMMU mode (can't do COW)
35 * - no readahead or I/O queue unplugging required
36 */
37struct backing_dev_info directly_mappable_cdev_bdi = {
38 .capabilities = (
39#ifdef CONFIG_MMU
40 /* permit private copies of the data to be taken */
41 BDI_CAP_MAP_COPY |
42#endif
43 /* permit direct mmap, for read, write or exec */
44 BDI_CAP_MAP_DIRECT |
45 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),
46};
47
Linus Torvalds1da177e2005-04-16 15:20:36 -070048static struct kobj_map *cdev_map;
49
Jes Sorensen58383af2006-02-06 14:12:43 -080050static DEFINE_MUTEX(chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070051
52static struct char_device_struct {
53 struct char_device_struct *next;
54 unsigned int major;
55 unsigned int baseminor;
56 int minorct;
Neil Horman7170be52006-01-14 13:20:38 -080057 char name[64];
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 struct file_operations *fops;
59 struct cdev *cdev; /* will die */
Joe Korty68eef3b2006-03-31 02:30:32 -080060} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
62/* index in the above */
63static inline int major_to_index(int major)
64{
Joe Korty68eef3b2006-03-31 02:30:32 -080065 return major % CHRDEV_MAJOR_HASH_SIZE;
Linus Torvalds1da177e2005-04-16 15:20:36 -070066}
67
Joe Korty68eef3b2006-03-31 02:30:32 -080068#ifdef CONFIG_PROC_FS
Neil Horman7170be52006-01-14 13:20:38 -080069
Joe Korty68eef3b2006-03-31 02:30:32 -080070void chrdev_show(struct seq_file *f, off_t offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
72 struct char_device_struct *cd;
Linus Torvalds1da177e2005-04-16 15:20:36 -070073
Joe Korty68eef3b2006-03-31 02:30:32 -080074 if (offset < CHRDEV_MAJOR_HASH_SIZE) {
75 mutex_lock(&chrdevs_lock);
76 for (cd = chrdevs[offset]; cd; cd = cd->next)
77 seq_printf(f, "%3d %s\n", cd->major, cd->name);
78 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 }
Neil Horman7170be52006-01-14 13:20:38 -080080}
81
Joe Korty68eef3b2006-03-31 02:30:32 -080082#endif /* CONFIG_PROC_FS */
Linus Torvalds1da177e2005-04-16 15:20:36 -070083
84/*
85 * Register a single major with a specified minor range.
86 *
87 * If major == 0 this functions will dynamically allocate a major and return
88 * its number.
89 *
90 * If major > 0 this function will attempt to reserve the passed range of
91 * minors and will return zero on success.
92 *
93 * Returns a -ve errno on failure.
94 */
95static struct char_device_struct *
96__register_chrdev_region(unsigned int major, unsigned int baseminor,
97 int minorct, const char *name)
98{
99 struct char_device_struct *cd, **cp;
100 int ret = 0;
101 int i;
102
Oliver Neukum11b0b5a2006-03-25 03:08:13 -0800103 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 if (cd == NULL)
105 return ERR_PTR(-ENOMEM);
106
Jes Sorensen58383af2006-02-06 14:12:43 -0800107 mutex_lock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108
109 /* temporary */
110 if (major == 0) {
111 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
112 if (chrdevs[i] == NULL)
113 break;
114 }
115
116 if (i == 0) {
117 ret = -EBUSY;
118 goto out;
119 }
120 major = i;
121 ret = major;
122 }
123
124 cd->major = major;
125 cd->baseminor = baseminor;
126 cd->minorct = minorct;
Neil Horman7170be52006-01-14 13:20:38 -0800127 strncpy(cd->name,name, 64);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128
129 i = major_to_index(major);
130
131 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
132 if ((*cp)->major > major ||
Amos Waterland01d553d2006-09-29 02:00:08 -0700133 ((*cp)->major == major &&
134 (((*cp)->baseminor >= baseminor) ||
135 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 break;
Amos Waterland01d553d2006-09-29 02:00:08 -0700137
138 /* Check for overlapping minor ranges. */
139 if (*cp && (*cp)->major == major) {
140 int old_min = (*cp)->baseminor;
141 int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
142 int new_min = baseminor;
143 int new_max = baseminor + minorct - 1;
144
145 /* New driver overlaps from the left. */
146 if (new_max >= old_min && new_max <= old_max) {
147 ret = -EBUSY;
148 goto out;
149 }
150
151 /* New driver overlaps from the right. */
152 if (new_min <= old_max && new_min >= old_min) {
153 ret = -EBUSY;
154 goto out;
155 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 }
Amos Waterland01d553d2006-09-29 02:00:08 -0700157
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 cd->next = *cp;
159 *cp = cd;
Jes Sorensen58383af2006-02-06 14:12:43 -0800160 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 return cd;
162out:
Jes Sorensen58383af2006-02-06 14:12:43 -0800163 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164 kfree(cd);
165 return ERR_PTR(ret);
166}
167
168static struct char_device_struct *
169__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
170{
171 struct char_device_struct *cd = NULL, **cp;
172 int i = major_to_index(major);
173
Jes Sorensen58383af2006-02-06 14:12:43 -0800174 mutex_lock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
176 if ((*cp)->major == major &&
177 (*cp)->baseminor == baseminor &&
178 (*cp)->minorct == minorct)
179 break;
180 if (*cp) {
181 cd = *cp;
182 *cp = cd->next;
183 }
Jes Sorensen58383af2006-02-06 14:12:43 -0800184 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 return cd;
186}
187
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700188/**
189 * register_chrdev_region() - register a range of device numbers
190 * @from: the first in the desired range of device numbers; must include
191 * the major number.
192 * @count: the number of consecutive device numbers required
193 * @name: the name of the device or driver.
194 *
195 * Return value is zero on success, a negative error code on failure.
196 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197int register_chrdev_region(dev_t from, unsigned count, const char *name)
198{
199 struct char_device_struct *cd;
200 dev_t to = from + count;
201 dev_t n, next;
202
203 for (n = from; n < to; n = next) {
204 next = MKDEV(MAJOR(n)+1, 0);
205 if (next > to)
206 next = to;
207 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
208 next - n, name);
209 if (IS_ERR(cd))
210 goto fail;
211 }
212 return 0;
213fail:
214 to = n;
215 for (n = from; n < to; n = next) {
216 next = MKDEV(MAJOR(n)+1, 0);
217 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
218 }
219 return PTR_ERR(cd);
220}
221
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700222/**
223 * alloc_chrdev_region() - register a range of char device numbers
224 * @dev: output parameter for first assigned number
225 * @baseminor: first of the requested range of minor numbers
226 * @count: the number of minor numbers required
227 * @name: the name of the associated device or driver
228 *
229 * Allocates a range of char device numbers. The major number will be
230 * chosen dynamically, and returned (along with the first minor number)
231 * in @dev. Returns zero or a negative error code.
232 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
234 const char *name)
235{
236 struct char_device_struct *cd;
237 cd = __register_chrdev_region(0, baseminor, count, name);
238 if (IS_ERR(cd))
239 return PTR_ERR(cd);
240 *dev = MKDEV(cd->major, cd->baseminor);
241 return 0;
242}
243
Rolf Eike Beerd247e2c2006-07-14 00:24:23 -0700244/**
245 * register_chrdev() - Register a major number for character devices.
246 * @major: major device number or 0 for dynamic allocation
247 * @name: name of this range of devices
248 * @fops: file operations associated with this devices
249 *
250 * If @major == 0 this functions will dynamically allocate a major and return
251 * its number.
252 *
253 * If @major > 0 this function will attempt to reserve a device with the given
254 * major number and will return zero on success.
255 *
256 * Returns a -ve errno on failure.
257 *
258 * The name of this device has nothing to do with the name of the device in
259 * /dev. It only helps to keep track of the different owners of devices. If
260 * your module name has only one type of devices it's ok to use e.g. the name
261 * of the module here.
262 *
263 * This function registers a range of 256 minor numbers. The first minor number
264 * is 0.
265 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266int register_chrdev(unsigned int major, const char *name,
Arjan van de Ven99ac48f2006-03-28 01:56:41 -0800267 const struct file_operations *fops)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268{
269 struct char_device_struct *cd;
270 struct cdev *cdev;
271 char *s;
272 int err = -ENOMEM;
273
274 cd = __register_chrdev_region(major, 0, 256, name);
275 if (IS_ERR(cd))
276 return PTR_ERR(cd);
277
278 cdev = cdev_alloc();
279 if (!cdev)
280 goto out2;
281
282 cdev->owner = fops->owner;
283 cdev->ops = fops;
284 kobject_set_name(&cdev->kobj, "%s", name);
285 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
286 *s = '!';
287
288 err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
289 if (err)
290 goto out;
291
292 cd->cdev = cdev;
293
294 return major ? 0 : cd->major;
295out:
296 kobject_put(&cdev->kobj);
297out2:
298 kfree(__unregister_chrdev_region(cd->major, 0, 256));
299 return err;
300}
301
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700302/**
303 * unregister_chrdev_region() - return a range of device numbers
304 * @from: the first in the range of numbers to unregister
305 * @count: the number of device numbers to unregister
306 *
307 * This function will unregister a range of @count device numbers,
308 * starting with @from. The caller should normally be the one who
309 * allocated those numbers in the first place...
310 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311void unregister_chrdev_region(dev_t from, unsigned count)
312{
313 dev_t to = from + count;
314 dev_t n, next;
315
316 for (n = from; n < to; n = next) {
317 next = MKDEV(MAJOR(n)+1, 0);
318 if (next > to)
319 next = to;
320 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
321 }
322}
323
Akinobu Mitae53252d2007-07-19 01:47:51 -0700324void unregister_chrdev(unsigned int major, const char *name)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325{
326 struct char_device_struct *cd;
327 cd = __unregister_chrdev_region(major, 0, 256);
328 if (cd && cd->cdev)
329 cdev_del(cd->cdev);
330 kfree(cd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331}
332
333static DEFINE_SPINLOCK(cdev_lock);
334
335static struct kobject *cdev_get(struct cdev *p)
336{
337 struct module *owner = p->owner;
338 struct kobject *kobj;
339
340 if (owner && !try_module_get(owner))
341 return NULL;
342 kobj = kobject_get(&p->kobj);
343 if (!kobj)
344 module_put(owner);
345 return kobj;
346}
347
348void cdev_put(struct cdev *p)
349{
350 if (p) {
Brian King7da68442005-07-12 13:58:30 -0700351 struct module *owner = p->owner;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 kobject_put(&p->kobj);
Brian King7da68442005-07-12 13:58:30 -0700353 module_put(owner);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 }
355}
356
357/*
358 * Called every time a character special file is opened
359 */
360int chrdev_open(struct inode * inode, struct file * filp)
361{
362 struct cdev *p;
363 struct cdev *new = NULL;
364 int ret = 0;
365
366 spin_lock(&cdev_lock);
367 p = inode->i_cdev;
368 if (!p) {
369 struct kobject *kobj;
370 int idx;
371 spin_unlock(&cdev_lock);
372 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
373 if (!kobj)
374 return -ENXIO;
375 new = container_of(kobj, struct cdev, kobj);
376 spin_lock(&cdev_lock);
377 p = inode->i_cdev;
378 if (!p) {
379 inode->i_cdev = p = new;
380 inode->i_cindex = idx;
381 list_add(&inode->i_devices, &p->list);
382 new = NULL;
383 } else if (!cdev_get(p))
384 ret = -ENXIO;
385 } else if (!cdev_get(p))
386 ret = -ENXIO;
387 spin_unlock(&cdev_lock);
388 cdev_put(new);
389 if (ret)
390 return ret;
391 filp->f_op = fops_get(p->ops);
392 if (!filp->f_op) {
393 cdev_put(p);
394 return -ENXIO;
395 }
396 if (filp->f_op->open) {
397 lock_kernel();
398 ret = filp->f_op->open(inode,filp);
399 unlock_kernel();
400 }
401 if (ret)
402 cdev_put(p);
403 return ret;
404}
405
406void cd_forget(struct inode *inode)
407{
408 spin_lock(&cdev_lock);
409 list_del_init(&inode->i_devices);
410 inode->i_cdev = NULL;
411 spin_unlock(&cdev_lock);
412}
413
Adrian Bunk75c96f82005-05-05 16:16:09 -0700414static void cdev_purge(struct cdev *cdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415{
416 spin_lock(&cdev_lock);
417 while (!list_empty(&cdev->list)) {
418 struct inode *inode;
419 inode = container_of(cdev->list.next, struct inode, i_devices);
420 list_del_init(&inode->i_devices);
421 inode->i_cdev = NULL;
422 }
423 spin_unlock(&cdev_lock);
424}
425
426/*
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...
430 */
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -0800431const struct file_operations def_chr_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 .open = chrdev_open,
433};
434
435static struct kobject *exact_match(dev_t dev, int *part, void *data)
436{
437 struct cdev *p = data;
438 return &p->kobj;
439}
440
441static int exact_lock(dev_t dev, void *data)
442{
443 struct cdev *p = data;
444 return cdev_get(p) ? 0 : -1;
445}
446
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700447/**
448 * cdev_add() - add a char device to the system
449 * @p: the cdev structure for the device
450 * @dev: the first device number for which this device is responsible
451 * @count: the number of consecutive minor numbers corresponding to this
452 * device
453 *
454 * cdev_add() adds the device represented by @p to the system, making it
455 * live immediately. A negative error code is returned on failure.
456 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457int cdev_add(struct cdev *p, dev_t dev, unsigned count)
458{
459 p->dev = dev;
460 p->count = count;
461 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
462}
463
464static void cdev_unmap(dev_t dev, unsigned count)
465{
466 kobj_unmap(cdev_map, dev, count);
467}
468
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700469/**
470 * cdev_del() - remove a cdev from the system
471 * @p: the cdev structure to be removed
472 *
473 * cdev_del() removes @p from the system, possibly freeing the structure
474 * itself.
475 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476void cdev_del(struct cdev *p)
477{
478 cdev_unmap(p->dev, p->count);
479 kobject_put(&p->kobj);
480}
481
482
483static void cdev_default_release(struct kobject *kobj)
484{
485 struct cdev *p = container_of(kobj, struct cdev, kobj);
486 cdev_purge(p);
487}
488
489static void cdev_dynamic_release(struct kobject *kobj)
490{
491 struct cdev *p = container_of(kobj, struct cdev, kobj);
492 cdev_purge(p);
493 kfree(p);
494}
495
496static struct kobj_type ktype_cdev_default = {
497 .release = cdev_default_release,
498};
499
500static struct kobj_type ktype_cdev_dynamic = {
501 .release = cdev_dynamic_release,
502};
503
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700504/**
505 * cdev_alloc() - allocate a cdev structure
506 *
507 * Allocates and returns a cdev structure, or NULL on failure.
508 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509struct cdev *cdev_alloc(void)
510{
Oliver Neukum11b0b5a2006-03-25 03:08:13 -0800511 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 if (p) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 INIT_LIST_HEAD(&p->list);
Greg Kroah-Hartmanf9cb0742007-12-17 23:05:35 -0700514 kobject_init(&p->kobj, &ktype_cdev_dynamic);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 }
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);
Greg Kroah-Hartmanf9cb0742007-12-17 23:05:35 -0700531 kobject_init(&cdev->kobj, &ktype_cdev_default);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 cdev->ops = fops;
533}
534
535static struct kobject *base_probe(dev_t dev, int *part, void *data)
536{
537 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
538 /* Make old-style 2.4 aliases work */
539 request_module("char-major-%d", MAJOR(dev));
540 return NULL;
541}
542
543void __init chrdev_init(void)
544{
545 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -0700546 bdi_init(&directly_mappable_cdev_bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547}
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);