blob: a745b1d9e5458684205c38da349d7e850ff66d81 [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
7#include <linux/config.h>
8#include <linux/init.h>
9#include <linux/fs.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/devfs_fs_kernel.h>
18
19#include <linux/kobject.h>
20#include <linux/kobj_map.h>
21#include <linux/cdev.h>
22
23#ifdef CONFIG_KMOD
24#include <linux/kmod.h>
25#endif
26
27static struct kobj_map *cdev_map;
28
David Brownell1d4d5b32005-04-17 10:57:20 -070029#define MAX_PROBE_HASH 255 /* random */
Linus Torvalds1da177e2005-04-16 15:20:36 -070030
31static DECLARE_MUTEX(chrdevs_lock);
32
33static struct char_device_struct {
34 struct char_device_struct *next;
35 unsigned int major;
36 unsigned int baseminor;
37 int minorct;
38 const char *name;
39 struct file_operations *fops;
40 struct cdev *cdev; /* will die */
41} *chrdevs[MAX_PROBE_HASH];
42
43/* index in the above */
44static inline int major_to_index(int major)
45{
46 return major % MAX_PROBE_HASH;
47}
48
49/* get char device names in somewhat random order */
50int get_chrdev_list(char *page)
51{
52 struct char_device_struct *cd;
53 int i, len;
54
55 len = sprintf(page, "Character devices:\n");
56
57 down(&chrdevs_lock);
58 for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
59 for (cd = chrdevs[i]; cd; cd = cd->next)
60 len += sprintf(page+len, "%3d %s\n",
61 cd->major, cd->name);
62 }
63 up(&chrdevs_lock);
64
65 return len;
66}
67
68/*
69 * Register a single major with a specified minor range.
70 *
71 * If major == 0 this functions will dynamically allocate a major and return
72 * its number.
73 *
74 * If major > 0 this function will attempt to reserve the passed range of
75 * minors and will return zero on success.
76 *
77 * Returns a -ve errno on failure.
78 */
79static struct char_device_struct *
80__register_chrdev_region(unsigned int major, unsigned int baseminor,
81 int minorct, const char *name)
82{
83 struct char_device_struct *cd, **cp;
84 int ret = 0;
85 int i;
86
87 cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
88 if (cd == NULL)
89 return ERR_PTR(-ENOMEM);
90
91 memset(cd, 0, sizeof(struct char_device_struct));
92
93 down(&chrdevs_lock);
94
95 /* temporary */
96 if (major == 0) {
97 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
98 if (chrdevs[i] == NULL)
99 break;
100 }
101
102 if (i == 0) {
103 ret = -EBUSY;
104 goto out;
105 }
106 major = i;
107 ret = major;
108 }
109
110 cd->major = major;
111 cd->baseminor = baseminor;
112 cd->minorct = minorct;
113 cd->name = name;
114
115 i = major_to_index(major);
116
117 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
118 if ((*cp)->major > major ||
119 ((*cp)->major == major && (*cp)->baseminor >= baseminor))
120 break;
121 if (*cp && (*cp)->major == major &&
122 (*cp)->baseminor < baseminor + minorct) {
123 ret = -EBUSY;
124 goto out;
125 }
126 cd->next = *cp;
127 *cp = cd;
128 up(&chrdevs_lock);
129 return cd;
130out:
131 up(&chrdevs_lock);
132 kfree(cd);
133 return ERR_PTR(ret);
134}
135
136static struct char_device_struct *
137__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
138{
139 struct char_device_struct *cd = NULL, **cp;
140 int i = major_to_index(major);
141
142 up(&chrdevs_lock);
143 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
144 if ((*cp)->major == major &&
145 (*cp)->baseminor == baseminor &&
146 (*cp)->minorct == minorct)
147 break;
148 if (*cp) {
149 cd = *cp;
150 *cp = cd->next;
151 }
152 up(&chrdevs_lock);
153 return cd;
154}
155
156int register_chrdev_region(dev_t from, unsigned count, const char *name)
157{
158 struct char_device_struct *cd;
159 dev_t to = from + count;
160 dev_t n, next;
161
162 for (n = from; n < to; n = next) {
163 next = MKDEV(MAJOR(n)+1, 0);
164 if (next > to)
165 next = to;
166 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
167 next - n, name);
168 if (IS_ERR(cd))
169 goto fail;
170 }
171 return 0;
172fail:
173 to = n;
174 for (n = from; n < to; n = next) {
175 next = MKDEV(MAJOR(n)+1, 0);
176 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
177 }
178 return PTR_ERR(cd);
179}
180
181int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
182 const char *name)
183{
184 struct char_device_struct *cd;
185 cd = __register_chrdev_region(0, baseminor, count, name);
186 if (IS_ERR(cd))
187 return PTR_ERR(cd);
188 *dev = MKDEV(cd->major, cd->baseminor);
189 return 0;
190}
191
192int register_chrdev(unsigned int major, const char *name,
193 struct file_operations *fops)
194{
195 struct char_device_struct *cd;
196 struct cdev *cdev;
197 char *s;
198 int err = -ENOMEM;
199
200 cd = __register_chrdev_region(major, 0, 256, name);
201 if (IS_ERR(cd))
202 return PTR_ERR(cd);
203
204 cdev = cdev_alloc();
205 if (!cdev)
206 goto out2;
207
208 cdev->owner = fops->owner;
209 cdev->ops = fops;
210 kobject_set_name(&cdev->kobj, "%s", name);
211 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
212 *s = '!';
213
214 err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
215 if (err)
216 goto out;
217
218 cd->cdev = cdev;
219
220 return major ? 0 : cd->major;
221out:
222 kobject_put(&cdev->kobj);
223out2:
224 kfree(__unregister_chrdev_region(cd->major, 0, 256));
225 return err;
226}
227
228void unregister_chrdev_region(dev_t from, unsigned count)
229{
230 dev_t to = from + count;
231 dev_t n, next;
232
233 for (n = from; n < to; n = next) {
234 next = MKDEV(MAJOR(n)+1, 0);
235 if (next > to)
236 next = to;
237 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
238 }
239}
240
241int unregister_chrdev(unsigned int major, const char *name)
242{
243 struct char_device_struct *cd;
244 cd = __unregister_chrdev_region(major, 0, 256);
245 if (cd && cd->cdev)
246 cdev_del(cd->cdev);
247 kfree(cd);
248 return 0;
249}
250
251static DEFINE_SPINLOCK(cdev_lock);
252
253static struct kobject *cdev_get(struct cdev *p)
254{
255 struct module *owner = p->owner;
256 struct kobject *kobj;
257
258 if (owner && !try_module_get(owner))
259 return NULL;
260 kobj = kobject_get(&p->kobj);
261 if (!kobj)
262 module_put(owner);
263 return kobj;
264}
265
266void cdev_put(struct cdev *p)
267{
268 if (p) {
269 kobject_put(&p->kobj);
270 module_put(p->owner);
271 }
272}
273
274/*
275 * Called every time a character special file is opened
276 */
277int chrdev_open(struct inode * inode, struct file * filp)
278{
279 struct cdev *p;
280 struct cdev *new = NULL;
281 int ret = 0;
282
283 spin_lock(&cdev_lock);
284 p = inode->i_cdev;
285 if (!p) {
286 struct kobject *kobj;
287 int idx;
288 spin_unlock(&cdev_lock);
289 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
290 if (!kobj)
291 return -ENXIO;
292 new = container_of(kobj, struct cdev, kobj);
293 spin_lock(&cdev_lock);
294 p = inode->i_cdev;
295 if (!p) {
296 inode->i_cdev = p = new;
297 inode->i_cindex = idx;
298 list_add(&inode->i_devices, &p->list);
299 new = NULL;
300 } else if (!cdev_get(p))
301 ret = -ENXIO;
302 } else if (!cdev_get(p))
303 ret = -ENXIO;
304 spin_unlock(&cdev_lock);
305 cdev_put(new);
306 if (ret)
307 return ret;
308 filp->f_op = fops_get(p->ops);
309 if (!filp->f_op) {
310 cdev_put(p);
311 return -ENXIO;
312 }
313 if (filp->f_op->open) {
314 lock_kernel();
315 ret = filp->f_op->open(inode,filp);
316 unlock_kernel();
317 }
318 if (ret)
319 cdev_put(p);
320 return ret;
321}
322
323void cd_forget(struct inode *inode)
324{
325 spin_lock(&cdev_lock);
326 list_del_init(&inode->i_devices);
327 inode->i_cdev = NULL;
328 spin_unlock(&cdev_lock);
329}
330
331void cdev_purge(struct cdev *cdev)
332{
333 spin_lock(&cdev_lock);
334 while (!list_empty(&cdev->list)) {
335 struct inode *inode;
336 inode = container_of(cdev->list.next, struct inode, i_devices);
337 list_del_init(&inode->i_devices);
338 inode->i_cdev = NULL;
339 }
340 spin_unlock(&cdev_lock);
341}
342
343/*
344 * Dummy default file-operations: the only thing this does
345 * is contain the open that then fills in the correct operations
346 * depending on the special file...
347 */
348struct file_operations def_chr_fops = {
349 .open = chrdev_open,
350};
351
352static struct kobject *exact_match(dev_t dev, int *part, void *data)
353{
354 struct cdev *p = data;
355 return &p->kobj;
356}
357
358static int exact_lock(dev_t dev, void *data)
359{
360 struct cdev *p = data;
361 return cdev_get(p) ? 0 : -1;
362}
363
364int cdev_add(struct cdev *p, dev_t dev, unsigned count)
365{
366 p->dev = dev;
367 p->count = count;
368 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
369}
370
371static void cdev_unmap(dev_t dev, unsigned count)
372{
373 kobj_unmap(cdev_map, dev, count);
374}
375
376void cdev_del(struct cdev *p)
377{
378 cdev_unmap(p->dev, p->count);
379 kobject_put(&p->kobj);
380}
381
382
383static void cdev_default_release(struct kobject *kobj)
384{
385 struct cdev *p = container_of(kobj, struct cdev, kobj);
386 cdev_purge(p);
387}
388
389static void cdev_dynamic_release(struct kobject *kobj)
390{
391 struct cdev *p = container_of(kobj, struct cdev, kobj);
392 cdev_purge(p);
393 kfree(p);
394}
395
396static struct kobj_type ktype_cdev_default = {
397 .release = cdev_default_release,
398};
399
400static struct kobj_type ktype_cdev_dynamic = {
401 .release = cdev_dynamic_release,
402};
403
404struct cdev *cdev_alloc(void)
405{
406 struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
407 if (p) {
408 memset(p, 0, sizeof(struct cdev));
409 p->kobj.ktype = &ktype_cdev_dynamic;
410 INIT_LIST_HEAD(&p->list);
411 kobject_init(&p->kobj);
412 }
413 return p;
414}
415
416void cdev_init(struct cdev *cdev, struct file_operations *fops)
417{
418 memset(cdev, 0, sizeof *cdev);
419 INIT_LIST_HEAD(&cdev->list);
420 cdev->kobj.ktype = &ktype_cdev_default;
421 kobject_init(&cdev->kobj);
422 cdev->ops = fops;
423}
424
425static struct kobject *base_probe(dev_t dev, int *part, void *data)
426{
427 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
428 /* Make old-style 2.4 aliases work */
429 request_module("char-major-%d", MAJOR(dev));
430 return NULL;
431}
432
433void __init chrdev_init(void)
434{
435 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
436}
437
438
439/* Let modules do char dev stuff */
440EXPORT_SYMBOL(register_chrdev_region);
441EXPORT_SYMBOL(unregister_chrdev_region);
442EXPORT_SYMBOL(alloc_chrdev_region);
443EXPORT_SYMBOL(cdev_init);
444EXPORT_SYMBOL(cdev_alloc);
445EXPORT_SYMBOL(cdev_del);
446EXPORT_SYMBOL(cdev_add);
447EXPORT_SYMBOL(register_chrdev);
448EXPORT_SYMBOL(unregister_chrdev);