projects/linux·blob v2.6.13 · refs

460 lines · 9.5 KiB

1/*
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
29#define MAX_PROBE_HASH 255 /* random */
30
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 /*
61 * if the current name, plus the 5 extra characters
62 * in the device line for this entry
63 * would run us off the page, we're done
64 */
65 if ((len+strlen(cd->name) + 5) >= PAGE_SIZE)
66 goto page_full;
67
68
69 len += sprintf(page+len, "%3d %s\n",
70 cd->major, cd->name);
71 }
72 }
73page_full:
74 up(&chrdevs_lock);
75
76 return len;
77}
78
79/*
80 * Register a single major with a specified minor range.
81 *
82 * If major == 0 this functions will dynamically allocate a major and return
83 * its number.
84 *
85 * If major > 0 this function will attempt to reserve the passed range of
86 * minors and will return zero on success.
87 *
88 * Returns a -ve errno on failure.
89 */
90static struct char_device_struct *
91__register_chrdev_region(unsigned int major, unsigned int baseminor,
92 int minorct, const char *name)
93{
94 struct char_device_struct *cd, **cp;
95 int ret = 0;
96 int i;
97
98 cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
99 if (cd == NULL)
100 return ERR_PTR(-ENOMEM);
101
102 memset(cd, 0, sizeof(struct char_device_struct));
103
104 down(&chrdevs_lock);
105
106 /* temporary */
107 if (major == 0) {
108 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
109 if (chrdevs[i] == NULL)
110 break;
111 }
112
113 if (i == 0) {
114 ret = -EBUSY;
115 goto out;
116 }
117 major = i;
118 ret = major;
119 }
120
121 cd->major = major;
122 cd->baseminor = baseminor;
123 cd->minorct = minorct;
124 cd->name = name;
125
126 i = major_to_index(major);
127
128 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
129 if ((*cp)->major > major ||
130 ((*cp)->major == major && (*cp)->baseminor >= baseminor))
131 break;
132 if (*cp && (*cp)->major == major &&
133 (*cp)->baseminor < baseminor + minorct) {
134 ret = -EBUSY;
135 goto out;
136 }
137 cd->next = *cp;
138 *cp = cd;
139 up(&chrdevs_lock);
140 return cd;
141out:
142 up(&chrdevs_lock);
143 kfree(cd);
144 return ERR_PTR(ret);
145}
146
147static struct char_device_struct *
148__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
149{
150 struct char_device_struct *cd = NULL, **cp;
151 int i = major_to_index(major);
152
153 down(&chrdevs_lock);
154 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
155 if ((*cp)->major == major &&
156 (*cp)->baseminor == baseminor &&
157 (*cp)->minorct == minorct)
158 break;
159 if (*cp) {
160 cd = *cp;
161 *cp = cd->next;
162 }
163 up(&chrdevs_lock);
164 return cd;
165}
166
167int register_chrdev_region(dev_t from, unsigned count, const char *name)
168{
169 struct char_device_struct *cd;
170 dev_t to = from + count;
171 dev_t n, next;
172
173 for (n = from; n < to; n = next) {
174 next = MKDEV(MAJOR(n)+1, 0);
175 if (next > to)
176 next = to;
177 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
178 next - n, name);
179 if (IS_ERR(cd))
180 goto fail;
181 }
182 return 0;
183fail:
184 to = n;
185 for (n = from; n < to; n = next) {
186 next = MKDEV(MAJOR(n)+1, 0);
187 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
188 }
189 return PTR_ERR(cd);
190}
191
192int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
193 const char *name)
194{
195 struct char_device_struct *cd;
196 cd = __register_chrdev_region(0, baseminor, count, name);
197 if (IS_ERR(cd))
198 return PTR_ERR(cd);
199 *dev = MKDEV(cd->major, cd->baseminor);
200 return 0;
201}
202
203int register_chrdev(unsigned int major, const char *name,
204 struct file_operations *fops)
205{
206 struct char_device_struct *cd;
207 struct cdev *cdev;
208 char *s;
209 int err = -ENOMEM;
210
211 cd = __register_chrdev_region(major, 0, 256, name);
212 if (IS_ERR(cd))
213 return PTR_ERR(cd);
214
215 cdev = cdev_alloc();
216 if (!cdev)
217 goto out2;
218
219 cdev->owner = fops->owner;
220 cdev->ops = fops;
221 kobject_set_name(&cdev->kobj, "%s", name);
222 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
223 *s = '!';
224
225 err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
226 if (err)
227 goto out;
228
229 cd->cdev = cdev;
230
231 return major ? 0 : cd->major;
232out:
233 kobject_put(&cdev->kobj);
234out2:
235 kfree(__unregister_chrdev_region(cd->major, 0, 256));
236 return err;
237}
238
239void unregister_chrdev_region(dev_t from, unsigned count)
240{
241 dev_t to = from + count;
242 dev_t n, next;
243
244 for (n = from; n < to; n = next) {
245 next = MKDEV(MAJOR(n)+1, 0);
246 if (next > to)
247 next = to;
248 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
249 }
250}
251
252int unregister_chrdev(unsigned int major, const char *name)
253{
254 struct char_device_struct *cd;
255 cd = __unregister_chrdev_region(major, 0, 256);
256 if (cd && cd->cdev)
257 cdev_del(cd->cdev);
258 kfree(cd);
259 return 0;
260}
261
262static DEFINE_SPINLOCK(cdev_lock);
263
264static struct kobject *cdev_get(struct cdev *p)
265{
266 struct module *owner = p->owner;
267 struct kobject *kobj;
268
269 if (owner && !try_module_get(owner))
270 return NULL;
271 kobj = kobject_get(&p->kobj);
272 if (!kobj)
273 module_put(owner);
274 return kobj;
275}
276
277void cdev_put(struct cdev *p)
278{
279 if (p) {
280 struct module *owner = p->owner;
281 kobject_put(&p->kobj);
282 module_put(owner);
283 }
284}
285
286/*
287 * Called every time a character special file is opened
288 */
289int chrdev_open(struct inode * inode, struct file * filp)
290{
291 struct cdev *p;
292 struct cdev *new = NULL;
293 int ret = 0;
294
295 spin_lock(&cdev_lock);
296 p = inode->i_cdev;
297 if (!p) {
298 struct kobject *kobj;
299 int idx;
300 spin_unlock(&cdev_lock);
301 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
302 if (!kobj)
303 return -ENXIO;
304 new = container_of(kobj, struct cdev, kobj);
305 spin_lock(&cdev_lock);
306 p = inode->i_cdev;
307 if (!p) {
308 inode->i_cdev = p = new;
309 inode->i_cindex = idx;
310 list_add(&inode->i_devices, &p->list);
311 new = NULL;
312 } else if (!cdev_get(p))
313 ret = -ENXIO;
314 } else if (!cdev_get(p))
315 ret = -ENXIO;
316 spin_unlock(&cdev_lock);
317 cdev_put(new);
318 if (ret)
319 return ret;
320 filp->f_op = fops_get(p->ops);
321 if (!filp->f_op) {
322 cdev_put(p);
323 return -ENXIO;
324 }
325 if (filp->f_op->open) {
326 lock_kernel();
327 ret = filp->f_op->open(inode,filp);
328 unlock_kernel();
329 }
330 if (ret)
331 cdev_put(p);
332 return ret;
333}
334
335void cd_forget(struct inode *inode)
336{
337 spin_lock(&cdev_lock);
338 list_del_init(&inode->i_devices);
339 inode->i_cdev = NULL;
340 spin_unlock(&cdev_lock);
341}
342
343static void cdev_purge(struct cdev *cdev)
344{
345 spin_lock(&cdev_lock);
346 while (!list_empty(&cdev->list)) {
347 struct inode *inode;
348 inode = container_of(cdev->list.next, struct inode, i_devices);
349 list_del_init(&inode->i_devices);
350 inode->i_cdev = NULL;
351 }
352 spin_unlock(&cdev_lock);
353}
354
355/*
356 * Dummy default file-operations: the only thing this does
357 * is contain the open that then fills in the correct operations
358 * depending on the special file...
359 */
360struct file_operations def_chr_fops = {
361 .open = chrdev_open,
362};
363
364static struct kobject *exact_match(dev_t dev, int *part, void *data)
365{
366 struct cdev *p = data;
367 return &p->kobj;
368}
369
370static int exact_lock(dev_t dev, void *data)
371{
372 struct cdev *p = data;
373 return cdev_get(p) ? 0 : -1;
374}
375
376int cdev_add(struct cdev *p, dev_t dev, unsigned count)
377{
378 p->dev = dev;
379 p->count = count;
380 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
381}
382
383static void cdev_unmap(dev_t dev, unsigned count)
384{
385 kobj_unmap(cdev_map, dev, count);
386}
387
388void cdev_del(struct cdev *p)
389{
390 cdev_unmap(p->dev, p->count);
391 kobject_put(&p->kobj);
392}
393
394
395static void cdev_default_release(struct kobject *kobj)
396{
397 struct cdev *p = container_of(kobj, struct cdev, kobj);
398 cdev_purge(p);
399}
400
401static void cdev_dynamic_release(struct kobject *kobj)
402{
403 struct cdev *p = container_of(kobj, struct cdev, kobj);
404 cdev_purge(p);
405 kfree(p);
406}
407
408static struct kobj_type ktype_cdev_default = {
409 .release = cdev_default_release,
410};
411
412static struct kobj_type ktype_cdev_dynamic = {
413 .release = cdev_dynamic_release,
414};
415
416struct cdev *cdev_alloc(void)
417{
418 struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
419 if (p) {
420 memset(p, 0, sizeof(struct cdev));
421 p->kobj.ktype = &ktype_cdev_dynamic;
422 INIT_LIST_HEAD(&p->list);
423 kobject_init(&p->kobj);
424 }
425 return p;
426}
427
428void cdev_init(struct cdev *cdev, struct file_operations *fops)
429{
430 memset(cdev, 0, sizeof *cdev);
431 INIT_LIST_HEAD(&cdev->list);
432 cdev->kobj.ktype = &ktype_cdev_default;
433 kobject_init(&cdev->kobj);
434 cdev->ops = fops;
435}
436
437static struct kobject *base_probe(dev_t dev, int *part, void *data)
438{
439 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
440 /* Make old-style 2.4 aliases work */
441 request_module("char-major-%d", MAJOR(dev));
442 return NULL;
443}
444
445void __init chrdev_init(void)
446{
447 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
448}
449
450
451/* Let modules do char dev stuff */
452EXPORT_SYMBOL(register_chrdev_region);
453EXPORT_SYMBOL(unregister_chrdev_region);
454EXPORT_SYMBOL(alloc_chrdev_region);
455EXPORT_SYMBOL(cdev_init);
456EXPORT_SYMBOL(cdev_alloc);
457EXPORT_SYMBOL(cdev_del);
458EXPORT_SYMBOL(cdev_add);
459EXPORT_SYMBOL(register_chrdev);
460EXPORT_SYMBOL(unregister_chrdev);