blob: a885f46ca001f117a9b8bc3bd4ac0e140b5c9e3e [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
David Howells07f3f05c2006-09-30 20:52:18 +020027#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070028
David Howells5da61852006-09-27 01:50:16 -070029/*
30 * capabilities for /dev/mem, /dev/kmem and similar directly mappable character
31 * devices
32 * - permits shared-mmap for read, write and/or exec
33 * - does not permit private mmap in NOMMU mode (can't do COW)
34 * - no readahead or I/O queue unplugging required
35 */
36struct backing_dev_info directly_mappable_cdev_bdi = {
37 .capabilities = (
38#ifdef CONFIG_MMU
39 /* permit private copies of the data to be taken */
40 BDI_CAP_MAP_COPY |
41#endif
42 /* permit direct mmap, for read, write or exec */
43 BDI_CAP_MAP_DIRECT |
44 BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),
45};
46
Linus Torvalds1da177e2005-04-16 15:20:36 -070047static struct kobj_map *cdev_map;
48
Jes Sorensen58383af2006-02-06 14:12:43 -080049static DEFINE_MUTEX(chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070050
51static struct char_device_struct {
52 struct char_device_struct *next;
53 unsigned int major;
54 unsigned int baseminor;
55 int minorct;
Neil Horman7170be52006-01-14 13:20:38 -080056 char name[64];
Linus Torvalds1da177e2005-04-16 15:20:36 -070057 struct file_operations *fops;
58 struct cdev *cdev; /* will die */
Joe Korty68eef3b2006-03-31 02:30:32 -080059} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
61/* index in the above */
62static inline int major_to_index(int major)
63{
Joe Korty68eef3b2006-03-31 02:30:32 -080064 return major % CHRDEV_MAJOR_HASH_SIZE;
Linus Torvalds1da177e2005-04-16 15:20:36 -070065}
66
Joe Korty68eef3b2006-03-31 02:30:32 -080067#ifdef CONFIG_PROC_FS
Neil Horman7170be52006-01-14 13:20:38 -080068
Joe Korty68eef3b2006-03-31 02:30:32 -080069void chrdev_show(struct seq_file *f, off_t offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -070070{
71 struct char_device_struct *cd;
Linus Torvalds1da177e2005-04-16 15:20:36 -070072
Joe Korty68eef3b2006-03-31 02:30:32 -080073 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);
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 }
Neil Horman7170be52006-01-14 13:20:38 -080079}
80
Joe Korty68eef3b2006-03-31 02:30:32 -080081#endif /* CONFIG_PROC_FS */
Linus Torvalds1da177e2005-04-16 15:20:36 -070082
83/*
84 * Register a single major with a specified minor range.
85 *
86 * If major == 0 this functions will dynamically allocate a major and return
87 * its number.
88 *
89 * If major > 0 this function will attempt to reserve the passed range of
90 * minors and will return zero on success.
91 *
92 * Returns a -ve errno on failure.
93 */
94static struct char_device_struct *
95__register_chrdev_region(unsigned int major, unsigned int baseminor,
96 int minorct, const char *name)
97{
98 struct char_device_struct *cd, **cp;
99 int ret = 0;
100 int i;
101
Oliver Neukum11b0b5a2006-03-25 03:08:13 -0800102 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 if (cd == NULL)
104 return ERR_PTR(-ENOMEM);
105
Jes Sorensen58383af2006-02-06 14:12:43 -0800106 mutex_lock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107
108 /* temporary */
109 if (major == 0) {
110 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
111 if (chrdevs[i] == NULL)
112 break;
113 }
114
115 if (i == 0) {
116 ret = -EBUSY;
117 goto out;
118 }
119 major = i;
120 ret = major;
121 }
122
123 cd->major = major;
124 cd->baseminor = baseminor;
125 cd->minorct = minorct;
Neil Horman7170be52006-01-14 13:20:38 -0800126 strncpy(cd->name,name, 64);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127
128 i = major_to_index(major);
129
130 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
131 if ((*cp)->major > major ||
Amos Waterland01d553d2006-09-29 02:00:08 -0700132 ((*cp)->major == major &&
133 (((*cp)->baseminor >= baseminor) ||
134 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 break;
Amos Waterland01d553d2006-09-29 02:00:08 -0700136
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;
143
144 /* New driver overlaps from the left. */
145 if (new_max >= old_min && new_max <= old_max) {
146 ret = -EBUSY;
147 goto out;
148 }
149
150 /* New driver overlaps from the right. */
151 if (new_min <= old_max && new_min >= old_min) {
152 ret = -EBUSY;
153 goto out;
154 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 }
Amos Waterland01d553d2006-09-29 02:00:08 -0700156
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 cd->next = *cp;
158 *cp = cd;
Jes Sorensen58383af2006-02-06 14:12:43 -0800159 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 return cd;
161out:
Jes Sorensen58383af2006-02-06 14:12:43 -0800162 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 kfree(cd);
164 return ERR_PTR(ret);
165}
166
167static struct char_device_struct *
168__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
169{
170 struct char_device_struct *cd = NULL, **cp;
171 int i = major_to_index(major);
172
Jes Sorensen58383af2006-02-06 14:12:43 -0800173 mutex_lock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
175 if ((*cp)->major == major &&
176 (*cp)->baseminor == baseminor &&
177 (*cp)->minorct == minorct)
178 break;
179 if (*cp) {
180 cd = *cp;
181 *cp = cd->next;
182 }
Jes Sorensen58383af2006-02-06 14:12:43 -0800183 mutex_unlock(&chrdevs_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184 return cd;
185}
186
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700187/**
188 * register_chrdev_region() - register a range of device numbers
189 * @from: the first in the desired range of device numbers; must include
190 * the major number.
191 * @count: the number of consecutive device numbers required
192 * @name: the name of the device or driver.
193 *
194 * Return value is zero on success, a negative error code on failure.
195 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196int register_chrdev_region(dev_t from, unsigned count, const char *name)
197{
198 struct char_device_struct *cd;
199 dev_t to = from + count;
200 dev_t n, next;
201
202 for (n = from; n < to; n = next) {
203 next = MKDEV(MAJOR(n)+1, 0);
204 if (next > to)
205 next = to;
206 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
207 next - n, name);
208 if (IS_ERR(cd))
209 goto fail;
210 }
211 return 0;
212fail:
213 to = 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));
217 }
218 return PTR_ERR(cd);
219}
220
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700221/**
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
227 *
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.
231 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
233 const char *name)
234{
235 struct char_device_struct *cd;
236 cd = __register_chrdev_region(0, baseminor, count, name);
237 if (IS_ERR(cd))
238 return PTR_ERR(cd);
239 *dev = MKDEV(cd->major, cd->baseminor);
240 return 0;
241}
242
Rolf Eike Beerd247e2c2006-07-14 00:24:23 -0700243/**
244 * register_chrdev() - Register a major number for character devices.
245 * @major: major device number or 0 for dynamic allocation
246 * @name: name of this range of devices
247 * @fops: file operations associated with this devices
248 *
249 * If @major == 0 this functions will dynamically allocate a major and return
250 * its number.
251 *
252 * If @major > 0 this function will attempt to reserve a device with the given
253 * major number and will return zero on success.
254 *
255 * Returns a -ve errno on failure.
256 *
257 * The name of this device has nothing to do with the name of the device in
258 * /dev. It only helps to keep track of the different owners of devices. If
259 * your module name has only one type of devices it's ok to use e.g. the name
260 * of the module here.
261 *
262 * This function registers a range of 256 minor numbers. The first minor number
263 * is 0.
264 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265int register_chrdev(unsigned int major, const char *name,
Arjan van de Ven99ac48f2006-03-28 01:56:41 -0800266 const struct file_operations *fops)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267{
268 struct char_device_struct *cd;
269 struct cdev *cdev;
270 char *s;
271 int err = -ENOMEM;
272
273 cd = __register_chrdev_region(major, 0, 256, name);
274 if (IS_ERR(cd))
275 return PTR_ERR(cd);
276
277 cdev = cdev_alloc();
278 if (!cdev)
279 goto out2;
280
281 cdev->owner = fops->owner;
282 cdev->ops = fops;
283 kobject_set_name(&cdev->kobj, "%s", name);
284 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
285 *s = '!';
286
287 err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
288 if (err)
289 goto out;
290
291 cd->cdev = cdev;
292
293 return major ? 0 : cd->major;
294out:
295 kobject_put(&cdev->kobj);
296out2:
297 kfree(__unregister_chrdev_region(cd->major, 0, 256));
298 return err;
299}
300
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700301/**
302 * unregister_chrdev_region() - return a range of device numbers
303 * @from: the first in the range of numbers to unregister
304 * @count: the number of device numbers to unregister
305 *
306 * This function will unregister a range of @count device numbers,
307 * starting with @from. The caller should normally be the one who
308 * allocated those numbers in the first place...
309 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310void unregister_chrdev_region(dev_t from, unsigned count)
311{
312 dev_t to = from + count;
313 dev_t n, next;
314
315 for (n = from; n < to; n = next) {
316 next = MKDEV(MAJOR(n)+1, 0);
317 if (next > to)
318 next = to;
319 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
320 }
321}
322
323int unregister_chrdev(unsigned int major, const char *name)
324{
325 struct char_device_struct *cd;
326 cd = __unregister_chrdev_region(major, 0, 256);
327 if (cd && cd->cdev)
328 cdev_del(cd->cdev);
329 kfree(cd);
330 return 0;
331}
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 p->kobj.ktype = &ktype_cdev_dynamic;
514 INIT_LIST_HEAD(&p->list);
515 kobject_init(&p->kobj);
516 }
517 return p;
518}
519
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700520/**
521 * cdev_init() - initialize a cdev structure
522 * @cdev: the structure to initialize
523 * @fops: the file_operations for this device
524 *
525 * Initializes @cdev, remembering @fops, making it ready to add to the
526 * system with cdev_add().
527 */
Arjan van de Ven99ac48f2006-03-28 01:56:41 -0800528void cdev_init(struct cdev *cdev, const struct file_operations *fops)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529{
530 memset(cdev, 0, sizeof *cdev);
531 INIT_LIST_HEAD(&cdev->list);
532 cdev->kobj.ktype = &ktype_cdev_default;
533 kobject_init(&cdev->kobj);
534 cdev->ops = fops;
535}
536
537static struct kobject *base_probe(dev_t dev, int *part, void *data)
538{
539 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
540 /* Make old-style 2.4 aliases work */
541 request_module("char-major-%d", MAJOR(dev));
542 return NULL;
543}
544
545void __init chrdev_init(void)
546{
547 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
548}
549
550
551/* Let modules do char dev stuff */
552EXPORT_SYMBOL(register_chrdev_region);
553EXPORT_SYMBOL(unregister_chrdev_region);
554EXPORT_SYMBOL(alloc_chrdev_region);
555EXPORT_SYMBOL(cdev_init);
556EXPORT_SYMBOL(cdev_alloc);
557EXPORT_SYMBOL(cdev_del);
558EXPORT_SYMBOL(cdev_add);
559EXPORT_SYMBOL(register_chrdev);
560EXPORT_SYMBOL(unregister_chrdev);
David Howells5da61852006-09-27 01:50:16 -0700561EXPORT_SYMBOL(directly_mappable_cdev_bdi);