blob: 3cb7cda3d780e95026142398f4c52cdf565d93b6 [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>
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 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
Akinobu Mitae53252d2007-07-19 01:47:51 -0700323void unregister_chrdev(unsigned int major, const char *name)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324{
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);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330}
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 */
Denis Cheng922f9cf2008-02-08 04:22:00 -0800359static int chrdev_open(struct inode *inode, struct file *filp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360{
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);
Jonathan Corbeta30427d2008-05-18 15:39:11 -0600376 /* Check i_cdev again in case somebody beat us to it while
377 we dropped the lock. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378 p = inode->i_cdev;
379 if (!p) {
380 inode->i_cdev = p = new;
381 inode->i_cindex = idx;
382 list_add(&inode->i_devices, &p->list);
383 new = NULL;
384 } else if (!cdev_get(p))
385 ret = -ENXIO;
386 } else if (!cdev_get(p))
387 ret = -ENXIO;
388 spin_unlock(&cdev_lock);
389 cdev_put(new);
390 if (ret)
391 return ret;
392 filp->f_op = fops_get(p->ops);
393 if (!filp->f_op) {
394 cdev_put(p);
395 return -ENXIO;
396 }
Jonathan Corbet9514dff2008-05-18 15:40:00 -0600397 if (filp->f_op->open)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 ret = filp->f_op->open(inode,filp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 if (ret)
400 cdev_put(p);
401 return ret;
402}
403
404void cd_forget(struct inode *inode)
405{
406 spin_lock(&cdev_lock);
407 list_del_init(&inode->i_devices);
408 inode->i_cdev = NULL;
409 spin_unlock(&cdev_lock);
410}
411
Adrian Bunk75c96f82005-05-05 16:16:09 -0700412static void cdev_purge(struct cdev *cdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413{
414 spin_lock(&cdev_lock);
415 while (!list_empty(&cdev->list)) {
416 struct inode *inode;
417 inode = container_of(cdev->list.next, struct inode, i_devices);
418 list_del_init(&inode->i_devices);
419 inode->i_cdev = NULL;
420 }
421 spin_unlock(&cdev_lock);
422}
423
424/*
425 * Dummy default file-operations: the only thing this does
426 * is contain the open that then fills in the correct operations
427 * depending on the special file...
428 */
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -0800429const struct file_operations def_chr_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 .open = chrdev_open,
431};
432
433static struct kobject *exact_match(dev_t dev, int *part, void *data)
434{
435 struct cdev *p = data;
436 return &p->kobj;
437}
438
439static int exact_lock(dev_t dev, void *data)
440{
441 struct cdev *p = data;
442 return cdev_get(p) ? 0 : -1;
443}
444
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700445/**
446 * cdev_add() - add a char device to the system
447 * @p: the cdev structure for the device
448 * @dev: the first device number for which this device is responsible
449 * @count: the number of consecutive minor numbers corresponding to this
450 * device
451 *
452 * cdev_add() adds the device represented by @p to the system, making it
453 * live immediately. A negative error code is returned on failure.
454 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455int cdev_add(struct cdev *p, dev_t dev, unsigned count)
456{
457 p->dev = dev;
458 p->count = count;
459 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
460}
461
462static void cdev_unmap(dev_t dev, unsigned count)
463{
464 kobj_unmap(cdev_map, dev, count);
465}
466
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700467/**
468 * cdev_del() - remove a cdev from the system
469 * @p: the cdev structure to be removed
470 *
471 * cdev_del() removes @p from the system, possibly freeing the structure
472 * itself.
473 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700474void cdev_del(struct cdev *p)
475{
476 cdev_unmap(p->dev, p->count);
477 kobject_put(&p->kobj);
478}
479
480
481static void cdev_default_release(struct kobject *kobj)
482{
483 struct cdev *p = container_of(kobj, struct cdev, kobj);
484 cdev_purge(p);
485}
486
487static void cdev_dynamic_release(struct kobject *kobj)
488{
489 struct cdev *p = container_of(kobj, struct cdev, kobj);
490 cdev_purge(p);
491 kfree(p);
492}
493
494static struct kobj_type ktype_cdev_default = {
495 .release = cdev_default_release,
496};
497
498static struct kobj_type ktype_cdev_dynamic = {
499 .release = cdev_dynamic_release,
500};
501
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700502/**
503 * cdev_alloc() - allocate a cdev structure
504 *
505 * Allocates and returns a cdev structure, or NULL on failure.
506 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507struct cdev *cdev_alloc(void)
508{
Oliver Neukum11b0b5a2006-03-25 03:08:13 -0800509 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 if (p) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 INIT_LIST_HEAD(&p->list);
Greg Kroah-Hartmanf9cb0742007-12-17 23:05:35 -0700512 kobject_init(&p->kobj, &ktype_cdev_dynamic);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 }
514 return p;
515}
516
Jonathan Corbetcf3e43d2006-09-29 02:00:44 -0700517/**
518 * cdev_init() - initialize a cdev structure
519 * @cdev: the structure to initialize
520 * @fops: the file_operations for this device
521 *
522 * Initializes @cdev, remembering @fops, making it ready to add to the
523 * system with cdev_add().
524 */
Arjan van de Ven99ac48f2006-03-28 01:56:41 -0800525void cdev_init(struct cdev *cdev, const struct file_operations *fops)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526{
527 memset(cdev, 0, sizeof *cdev);
528 INIT_LIST_HEAD(&cdev->list);
Greg Kroah-Hartmanf9cb0742007-12-17 23:05:35 -0700529 kobject_init(&cdev->kobj, &ktype_cdev_default);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 cdev->ops = fops;
531}
532
533static struct kobject *base_probe(dev_t dev, int *part, void *data)
534{
535 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
536 /* Make old-style 2.4 aliases work */
537 request_module("char-major-%d", MAJOR(dev));
538 return NULL;
539}
540
541void __init chrdev_init(void)
542{
543 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
Peter Zijlstrae0bf68d2007-10-16 23:25:46 -0700544 bdi_init(&directly_mappable_cdev_bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545}
546
547
548/* Let modules do char dev stuff */
549EXPORT_SYMBOL(register_chrdev_region);
550EXPORT_SYMBOL(unregister_chrdev_region);
551EXPORT_SYMBOL(alloc_chrdev_region);
552EXPORT_SYMBOL(cdev_init);
553EXPORT_SYMBOL(cdev_alloc);
554EXPORT_SYMBOL(cdev_del);
555EXPORT_SYMBOL(cdev_add);
556EXPORT_SYMBOL(register_chrdev);
557EXPORT_SYMBOL(unregister_chrdev);
David Howells5da61852006-09-27 01:50:16 -0700558EXPORT_SYMBOL(directly_mappable_cdev_bdi);