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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * linux/fs/char_dev.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | */ | |
6 | ||
1da177e4 LT |
7 | #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> | |
68eef3b4 | 16 | #include <linux/seq_file.h> |
1da177e4 LT |
17 | |
18 | #include <linux/kobject.h> | |
19 | #include <linux/kobj_map.h> | |
20 | #include <linux/cdev.h> | |
58383af6 | 21 | #include <linux/mutex.h> |
5da6185b | 22 | #include <linux/backing-dev.h> |
1da177e4 LT |
23 | |
24 | #ifdef CONFIG_KMOD | |
25 | #include <linux/kmod.h> | |
26 | #endif | |
27 | ||
5da6185b DH |
28 | /* |
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 | */ | |
35 | struct 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 | ||
1da177e4 LT |
46 | static struct kobj_map *cdev_map; |
47 | ||
58383af6 | 48 | static DEFINE_MUTEX(chrdevs_lock); |
1da177e4 LT |
49 | |
50 | static struct char_device_struct { | |
51 | struct char_device_struct *next; | |
52 | unsigned int major; | |
53 | unsigned int baseminor; | |
54 | int minorct; | |
7170be5f | 55 | char name[64]; |
1da177e4 LT |
56 | struct file_operations *fops; |
57 | struct cdev *cdev; /* will die */ | |
68eef3b4 | 58 | } *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; |
1da177e4 LT |
59 | |
60 | /* index in the above */ | |
61 | static inline int major_to_index(int major) | |
62 | { | |
68eef3b4 | 63 | return major % CHRDEV_MAJOR_HASH_SIZE; |
7170be5f NH |
64 | } |
65 | ||
68eef3b4 | 66 | #ifdef CONFIG_PROC_FS |
7170be5f | 67 | |
68eef3b4 | 68 | void chrdev_show(struct seq_file *f, off_t offset) |
7170be5f NH |
69 | { |
70 | struct char_device_struct *cd; | |
7170be5f | 71 | |
68eef3b4 JK |
72 | 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); | |
1da177e4 | 77 | } |
7170be5f NH |
78 | } |
79 | ||
68eef3b4 | 80 | #endif /* CONFIG_PROC_FS */ |
1da177e4 LT |
81 | |
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 | */ | |
93 | static 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 | ||
11b0b5ab | 101 | cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL); |
1da177e4 LT |
102 | if (cd == NULL) |
103 | return ERR_PTR(-ENOMEM); | |
104 | ||
58383af6 | 105 | mutex_lock(&chrdevs_lock); |
1da177e4 LT |
106 | |
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; | |
7170be5f | 125 | strncpy(cd->name,name, 64); |
1da177e4 LT |
126 | |
127 | i = major_to_index(major); | |
128 | ||
129 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) | |
130 | if ((*cp)->major > major || | |
131 | ((*cp)->major == major && (*cp)->baseminor >= baseminor)) | |
132 | break; | |
133 | if (*cp && (*cp)->major == major && | |
134 | (*cp)->baseminor < baseminor + minorct) { | |
135 | ret = -EBUSY; | |
136 | goto out; | |
137 | } | |
138 | cd->next = *cp; | |
139 | *cp = cd; | |
58383af6 | 140 | mutex_unlock(&chrdevs_lock); |
1da177e4 LT |
141 | return cd; |
142 | out: | |
58383af6 | 143 | mutex_unlock(&chrdevs_lock); |
1da177e4 LT |
144 | kfree(cd); |
145 | return ERR_PTR(ret); | |
146 | } | |
147 | ||
148 | static struct char_device_struct * | |
149 | __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) | |
150 | { | |
151 | struct char_device_struct *cd = NULL, **cp; | |
152 | int i = major_to_index(major); | |
153 | ||
58383af6 | 154 | mutex_lock(&chrdevs_lock); |
1da177e4 LT |
155 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) |
156 | if ((*cp)->major == major && | |
157 | (*cp)->baseminor == baseminor && | |
158 | (*cp)->minorct == minorct) | |
159 | break; | |
160 | if (*cp) { | |
161 | cd = *cp; | |
162 | *cp = cd->next; | |
163 | } | |
58383af6 | 164 | mutex_unlock(&chrdevs_lock); |
1da177e4 LT |
165 | return cd; |
166 | } | |
167 | ||
168 | int register_chrdev_region(dev_t from, unsigned count, const char *name) | |
169 | { | |
170 | struct char_device_struct *cd; | |
171 | dev_t to = from + count; | |
172 | dev_t n, next; | |
173 | ||
174 | for (n = from; n < to; n = next) { | |
175 | next = MKDEV(MAJOR(n)+1, 0); | |
176 | if (next > to) | |
177 | next = to; | |
178 | cd = __register_chrdev_region(MAJOR(n), MINOR(n), | |
179 | next - n, name); | |
180 | if (IS_ERR(cd)) | |
181 | goto fail; | |
182 | } | |
183 | return 0; | |
184 | fail: | |
185 | to = n; | |
186 | for (n = from; n < to; n = next) { | |
187 | next = MKDEV(MAJOR(n)+1, 0); | |
188 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); | |
189 | } | |
190 | return PTR_ERR(cd); | |
191 | } | |
192 | ||
193 | int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, | |
194 | const char *name) | |
195 | { | |
196 | struct char_device_struct *cd; | |
197 | cd = __register_chrdev_region(0, baseminor, count, name); | |
198 | if (IS_ERR(cd)) | |
199 | return PTR_ERR(cd); | |
200 | *dev = MKDEV(cd->major, cd->baseminor); | |
201 | return 0; | |
202 | } | |
203 | ||
d247e2c6 REB |
204 | /** |
205 | * register_chrdev() - Register a major number for character devices. | |
206 | * @major: major device number or 0 for dynamic allocation | |
207 | * @name: name of this range of devices | |
208 | * @fops: file operations associated with this devices | |
209 | * | |
210 | * If @major == 0 this functions will dynamically allocate a major and return | |
211 | * its number. | |
212 | * | |
213 | * If @major > 0 this function will attempt to reserve a device with the given | |
214 | * major number and will return zero on success. | |
215 | * | |
216 | * Returns a -ve errno on failure. | |
217 | * | |
218 | * The name of this device has nothing to do with the name of the device in | |
219 | * /dev. It only helps to keep track of the different owners of devices. If | |
220 | * your module name has only one type of devices it's ok to use e.g. the name | |
221 | * of the module here. | |
222 | * | |
223 | * This function registers a range of 256 minor numbers. The first minor number | |
224 | * is 0. | |
225 | */ | |
1da177e4 | 226 | int register_chrdev(unsigned int major, const char *name, |
99ac48f5 | 227 | const struct file_operations *fops) |
1da177e4 LT |
228 | { |
229 | struct char_device_struct *cd; | |
230 | struct cdev *cdev; | |
231 | char *s; | |
232 | int err = -ENOMEM; | |
233 | ||
234 | cd = __register_chrdev_region(major, 0, 256, name); | |
235 | if (IS_ERR(cd)) | |
236 | return PTR_ERR(cd); | |
237 | ||
238 | cdev = cdev_alloc(); | |
239 | if (!cdev) | |
240 | goto out2; | |
241 | ||
242 | cdev->owner = fops->owner; | |
243 | cdev->ops = fops; | |
244 | kobject_set_name(&cdev->kobj, "%s", name); | |
245 | for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')) | |
246 | *s = '!'; | |
247 | ||
248 | err = cdev_add(cdev, MKDEV(cd->major, 0), 256); | |
249 | if (err) | |
250 | goto out; | |
251 | ||
252 | cd->cdev = cdev; | |
253 | ||
254 | return major ? 0 : cd->major; | |
255 | out: | |
256 | kobject_put(&cdev->kobj); | |
257 | out2: | |
258 | kfree(__unregister_chrdev_region(cd->major, 0, 256)); | |
259 | return err; | |
260 | } | |
261 | ||
262 | void unregister_chrdev_region(dev_t from, unsigned count) | |
263 | { | |
264 | dev_t to = from + count; | |
265 | dev_t n, next; | |
266 | ||
267 | for (n = from; n < to; n = next) { | |
268 | next = MKDEV(MAJOR(n)+1, 0); | |
269 | if (next > to) | |
270 | next = to; | |
271 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); | |
272 | } | |
273 | } | |
274 | ||
275 | int unregister_chrdev(unsigned int major, const char *name) | |
276 | { | |
277 | struct char_device_struct *cd; | |
278 | cd = __unregister_chrdev_region(major, 0, 256); | |
279 | if (cd && cd->cdev) | |
280 | cdev_del(cd->cdev); | |
281 | kfree(cd); | |
282 | return 0; | |
283 | } | |
284 | ||
285 | static DEFINE_SPINLOCK(cdev_lock); | |
286 | ||
287 | static struct kobject *cdev_get(struct cdev *p) | |
288 | { | |
289 | struct module *owner = p->owner; | |
290 | struct kobject *kobj; | |
291 | ||
292 | if (owner && !try_module_get(owner)) | |
293 | return NULL; | |
294 | kobj = kobject_get(&p->kobj); | |
295 | if (!kobj) | |
296 | module_put(owner); | |
297 | return kobj; | |
298 | } | |
299 | ||
300 | void cdev_put(struct cdev *p) | |
301 | { | |
302 | if (p) { | |
7da6844c | 303 | struct module *owner = p->owner; |
1da177e4 | 304 | kobject_put(&p->kobj); |
7da6844c | 305 | module_put(owner); |
1da177e4 LT |
306 | } |
307 | } | |
308 | ||
309 | /* | |
310 | * Called every time a character special file is opened | |
311 | */ | |
312 | int chrdev_open(struct inode * inode, struct file * filp) | |
313 | { | |
314 | struct cdev *p; | |
315 | struct cdev *new = NULL; | |
316 | int ret = 0; | |
317 | ||
318 | spin_lock(&cdev_lock); | |
319 | p = inode->i_cdev; | |
320 | if (!p) { | |
321 | struct kobject *kobj; | |
322 | int idx; | |
323 | spin_unlock(&cdev_lock); | |
324 | kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); | |
325 | if (!kobj) | |
326 | return -ENXIO; | |
327 | new = container_of(kobj, struct cdev, kobj); | |
328 | spin_lock(&cdev_lock); | |
329 | p = inode->i_cdev; | |
330 | if (!p) { | |
331 | inode->i_cdev = p = new; | |
332 | inode->i_cindex = idx; | |
333 | list_add(&inode->i_devices, &p->list); | |
334 | new = NULL; | |
335 | } else if (!cdev_get(p)) | |
336 | ret = -ENXIO; | |
337 | } else if (!cdev_get(p)) | |
338 | ret = -ENXIO; | |
339 | spin_unlock(&cdev_lock); | |
340 | cdev_put(new); | |
341 | if (ret) | |
342 | return ret; | |
343 | filp->f_op = fops_get(p->ops); | |
344 | if (!filp->f_op) { | |
345 | cdev_put(p); | |
346 | return -ENXIO; | |
347 | } | |
348 | if (filp->f_op->open) { | |
349 | lock_kernel(); | |
350 | ret = filp->f_op->open(inode,filp); | |
351 | unlock_kernel(); | |
352 | } | |
353 | if (ret) | |
354 | cdev_put(p); | |
355 | return ret; | |
356 | } | |
357 | ||
358 | void cd_forget(struct inode *inode) | |
359 | { | |
360 | spin_lock(&cdev_lock); | |
361 | list_del_init(&inode->i_devices); | |
362 | inode->i_cdev = NULL; | |
363 | spin_unlock(&cdev_lock); | |
364 | } | |
365 | ||
75c96f85 | 366 | static void cdev_purge(struct cdev *cdev) |
1da177e4 LT |
367 | { |
368 | spin_lock(&cdev_lock); | |
369 | while (!list_empty(&cdev->list)) { | |
370 | struct inode *inode; | |
371 | inode = container_of(cdev->list.next, struct inode, i_devices); | |
372 | list_del_init(&inode->i_devices); | |
373 | inode->i_cdev = NULL; | |
374 | } | |
375 | spin_unlock(&cdev_lock); | |
376 | } | |
377 | ||
378 | /* | |
379 | * Dummy default file-operations: the only thing this does | |
380 | * is contain the open that then fills in the correct operations | |
381 | * depending on the special file... | |
382 | */ | |
4b6f5d20 | 383 | const struct file_operations def_chr_fops = { |
1da177e4 LT |
384 | .open = chrdev_open, |
385 | }; | |
386 | ||
387 | static struct kobject *exact_match(dev_t dev, int *part, void *data) | |
388 | { | |
389 | struct cdev *p = data; | |
390 | return &p->kobj; | |
391 | } | |
392 | ||
393 | static int exact_lock(dev_t dev, void *data) | |
394 | { | |
395 | struct cdev *p = data; | |
396 | return cdev_get(p) ? 0 : -1; | |
397 | } | |
398 | ||
399 | int cdev_add(struct cdev *p, dev_t dev, unsigned count) | |
400 | { | |
401 | p->dev = dev; | |
402 | p->count = count; | |
403 | return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); | |
404 | } | |
405 | ||
406 | static void cdev_unmap(dev_t dev, unsigned count) | |
407 | { | |
408 | kobj_unmap(cdev_map, dev, count); | |
409 | } | |
410 | ||
411 | void cdev_del(struct cdev *p) | |
412 | { | |
413 | cdev_unmap(p->dev, p->count); | |
414 | kobject_put(&p->kobj); | |
415 | } | |
416 | ||
417 | ||
418 | static void cdev_default_release(struct kobject *kobj) | |
419 | { | |
420 | struct cdev *p = container_of(kobj, struct cdev, kobj); | |
421 | cdev_purge(p); | |
422 | } | |
423 | ||
424 | static void cdev_dynamic_release(struct kobject *kobj) | |
425 | { | |
426 | struct cdev *p = container_of(kobj, struct cdev, kobj); | |
427 | cdev_purge(p); | |
428 | kfree(p); | |
429 | } | |
430 | ||
431 | static struct kobj_type ktype_cdev_default = { | |
432 | .release = cdev_default_release, | |
433 | }; | |
434 | ||
435 | static struct kobj_type ktype_cdev_dynamic = { | |
436 | .release = cdev_dynamic_release, | |
437 | }; | |
438 | ||
439 | struct cdev *cdev_alloc(void) | |
440 | { | |
11b0b5ab | 441 | struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); |
1da177e4 | 442 | if (p) { |
1da177e4 LT |
443 | p->kobj.ktype = &ktype_cdev_dynamic; |
444 | INIT_LIST_HEAD(&p->list); | |
445 | kobject_init(&p->kobj); | |
446 | } | |
447 | return p; | |
448 | } | |
449 | ||
99ac48f5 | 450 | void cdev_init(struct cdev *cdev, const struct file_operations *fops) |
1da177e4 LT |
451 | { |
452 | memset(cdev, 0, sizeof *cdev); | |
453 | INIT_LIST_HEAD(&cdev->list); | |
454 | cdev->kobj.ktype = &ktype_cdev_default; | |
455 | kobject_init(&cdev->kobj); | |
456 | cdev->ops = fops; | |
457 | } | |
458 | ||
459 | static struct kobject *base_probe(dev_t dev, int *part, void *data) | |
460 | { | |
461 | if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) | |
462 | /* Make old-style 2.4 aliases work */ | |
463 | request_module("char-major-%d", MAJOR(dev)); | |
464 | return NULL; | |
465 | } | |
466 | ||
467 | void __init chrdev_init(void) | |
468 | { | |
469 | cdev_map = kobj_map_init(base_probe, &chrdevs_lock); | |
470 | } | |
471 | ||
472 | ||
473 | /* Let modules do char dev stuff */ | |
474 | EXPORT_SYMBOL(register_chrdev_region); | |
475 | EXPORT_SYMBOL(unregister_chrdev_region); | |
476 | EXPORT_SYMBOL(alloc_chrdev_region); | |
477 | EXPORT_SYMBOL(cdev_init); | |
478 | EXPORT_SYMBOL(cdev_alloc); | |
479 | EXPORT_SYMBOL(cdev_del); | |
480 | EXPORT_SYMBOL(cdev_add); | |
481 | EXPORT_SYMBOL(register_chrdev); | |
482 | EXPORT_SYMBOL(unregister_chrdev); | |
5da6185b | 483 | EXPORT_SYMBOL(directly_mappable_cdev_bdi); |