projects/linux·blob v2.6.21 · refs

562 lines · 13.2 KiB

1/*
2 * linux/fs/char_dev.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7#include <linux/init.h>
8#include <linux/fs.h>
9#include <linux/kdev_t.h>
10#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>
17#include <linux/seq_file.h>
18
19#include <linux/kobject.h>
20#include <linux/kobj_map.h>
21#include <linux/cdev.h>
22#include <linux/mutex.h>
23#include <linux/backing-dev.h>
24
25#ifdef CONFIG_KMOD
26#include <linux/kmod.h>
27#endif
28#include "internal.h"
29
30/*
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
48static struct kobj_map *cdev_map;
49
50static DEFINE_MUTEX(chrdevs_lock);
51
52static struct char_device_struct {
53 struct char_device_struct *next;
54 unsigned int major;
55 unsigned int baseminor;
56 int minorct;
57 char name[64];
58 struct file_operations *fops;
59 struct cdev *cdev; /* will die */
60} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
61
62/* index in the above */
63static inline int major_to_index(int major)
64{
65 return major % CHRDEV_MAJOR_HASH_SIZE;
66}
67
68#ifdef CONFIG_PROC_FS
69
70void chrdev_show(struct seq_file *f, off_t offset)
71{
72 struct char_device_struct *cd;
73
74 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);
79 }
80}
81
82#endif /* CONFIG_PROC_FS */
83
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
103 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
104 if (cd == NULL)
105 return ERR_PTR(-ENOMEM);
106
107 mutex_lock(&chrdevs_lock);
108
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;
127 strncpy(cd->name,name, 64);
128
129 i = major_to_index(major);
130
131 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
132 if ((*cp)->major > major ||
133 ((*cp)->major == major &&
134 (((*cp)->baseminor >= baseminor) ||
135 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
136 break;
137
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 }
156 }
157
158 cd->next = *cp;
159 *cp = cd;
160 mutex_unlock(&chrdevs_lock);
161 return cd;
162out:
163 mutex_unlock(&chrdevs_lock);
164 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
174 mutex_lock(&chrdevs_lock);
175 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 }
184 mutex_unlock(&chrdevs_lock);
185 return cd;
186}
187
188/**
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 */
197int 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
222/**
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 */
233int 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
244/**
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 */
266int register_chrdev(unsigned int major, const char *name,
267 const struct file_operations *fops)
268{
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
302/**
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 */
311void 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
324int unregister_chrdev(unsigned int major, const char *name)
325{
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);
331 return 0;
332}
333
334static DEFINE_SPINLOCK(cdev_lock);
335
336static struct kobject *cdev_get(struct cdev *p)
337{
338 struct module *owner = p->owner;
339 struct kobject *kobj;
340
341 if (owner && !try_module_get(owner))
342 return NULL;
343 kobj = kobject_get(&p->kobj);
344 if (!kobj)
345 module_put(owner);
346 return kobj;
347}
348
349void cdev_put(struct cdev *p)
350{
351 if (p) {
352 struct module *owner = p->owner;
353 kobject_put(&p->kobj);
354 module_put(owner);
355 }
356}
357
358/*
359 * Called every time a character special file is opened
360 */
361int chrdev_open(struct inode * inode, struct file * filp)
362{
363 struct cdev *p;
364 struct cdev *new = NULL;
365 int ret = 0;
366
367 spin_lock(&cdev_lock);
368 p = inode->i_cdev;
369 if (!p) {
370 struct kobject *kobj;
371 int idx;
372 spin_unlock(&cdev_lock);
373 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
374 if (!kobj)
375 return -ENXIO;
376 new = container_of(kobj, struct cdev, kobj);
377 spin_lock(&cdev_lock);
378 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 }
397 if (filp->f_op->open) {
398 lock_kernel();
399 ret = filp->f_op->open(inode,filp);
400 unlock_kernel();
401 }
402 if (ret)
403 cdev_put(p);
404 return ret;
405}
406
407void cd_forget(struct inode *inode)
408{
409 spin_lock(&cdev_lock);
410 list_del_init(&inode->i_devices);
411 inode->i_cdev = NULL;
412 spin_unlock(&cdev_lock);
413}
414
415static void cdev_purge(struct cdev *cdev)
416{
417 spin_lock(&cdev_lock);
418 while (!list_empty(&cdev->list)) {
419 struct inode *inode;
420 inode = container_of(cdev->list.next, struct inode, i_devices);
421 list_del_init(&inode->i_devices);
422 inode->i_cdev = NULL;
423 }
424 spin_unlock(&cdev_lock);
425}
426
427/*
428 * Dummy default file-operations: the only thing this does
429 * is contain the open that then fills in the correct operations
430 * depending on the special file...
431 */
432const struct file_operations def_chr_fops = {
433 .open = chrdev_open,
434};
435
436static struct kobject *exact_match(dev_t dev, int *part, void *data)
437{
438 struct cdev *p = data;
439 return &p->kobj;
440}
441
442static int exact_lock(dev_t dev, void *data)
443{
444 struct cdev *p = data;
445 return cdev_get(p) ? 0 : -1;
446}
447
448/**
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
453 * device
454 *
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.
457 */
458int cdev_add(struct cdev *p, dev_t dev, unsigned count)
459{
460 p->dev = dev;
461 p->count = count;
462 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
463}
464
465static void cdev_unmap(dev_t dev, unsigned count)
466{
467 kobj_unmap(cdev_map, dev, count);
468}
469
470/**
471 * cdev_del() - remove a cdev from the system
472 * @p: the cdev structure to be removed
473 *
474 * cdev_del() removes @p from the system, possibly freeing the structure
475 * itself.
476 */
477void cdev_del(struct cdev *p)
478{
479 cdev_unmap(p->dev, p->count);
480 kobject_put(&p->kobj);
481}
482
483
484static void cdev_default_release(struct kobject *kobj)
485{
486 struct cdev *p = container_of(kobj, struct cdev, kobj);
487 cdev_purge(p);
488}
489
490static void cdev_dynamic_release(struct kobject *kobj)
491{
492 struct cdev *p = container_of(kobj, struct cdev, kobj);
493 cdev_purge(p);
494 kfree(p);
495}
496
497static struct kobj_type ktype_cdev_default = {
498 .release = cdev_default_release,
499};
500
501static struct kobj_type ktype_cdev_dynamic = {
502 .release = cdev_dynamic_release,
503};
504
505/**
506 * cdev_alloc() - allocate a cdev structure
507 *
508 * Allocates and returns a cdev structure, or NULL on failure.
509 */
510struct cdev *cdev_alloc(void)
511{
512 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
513 if (p) {
514 p->kobj.ktype = &ktype_cdev_dynamic;
515 INIT_LIST_HEAD(&p->list);
516 kobject_init(&p->kobj);
517 }
518 return p;
519}
520
521/**
522 * cdev_init() - initialize a cdev structure
523 * @cdev: the structure to initialize
524 * @fops: the file_operations for this device
525 *
526 * Initializes @cdev, remembering @fops, making it ready to add to the
527 * system with cdev_add().
528 */
529void cdev_init(struct cdev *cdev, const struct file_operations *fops)
530{
531 memset(cdev, 0, sizeof *cdev);
532 INIT_LIST_HEAD(&cdev->list);
533 cdev->kobj.ktype = &ktype_cdev_default;
534 kobject_init(&cdev->kobj);
535 cdev->ops = fops;
536}
537
538static struct kobject *base_probe(dev_t dev, int *part, void *data)
539{
540 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
541 /* Make old-style 2.4 aliases work */
542 request_module("char-major-%d", MAJOR(dev));
543 return NULL;
544}
545
546void __init chrdev_init(void)
547{
548 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
549}
550
551
552/* Let modules do char dev stuff */
553EXPORT_SYMBOL(register_chrdev_region);
554EXPORT_SYMBOL(unregister_chrdev_region);
555EXPORT_SYMBOL(alloc_chrdev_region);
556EXPORT_SYMBOL(cdev_init);
557EXPORT_SYMBOL(cdev_alloc);
558EXPORT_SYMBOL(cdev_del);
559EXPORT_SYMBOL(cdev_add);
560EXPORT_SYMBOL(register_chrdev);
561EXPORT_SYMBOL(unregister_chrdev);
562EXPORT_SYMBOL(directly_mappable_cdev_bdi);