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);
563