[net-next-2.6.git] / fs / char_dev.c

/*
 *  linux/fs/char_dev.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/config.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/string.h>

#include <linux/major.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/devfs_fs_kernel.h>

#include <linux/kobject.h>
#include <linux/kobj_map.h>
#include <linux/cdev.h>
#include <linux/mutex.h>

#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif

static struct kobj_map *cdev_map;

#define MAX_PROBE_HASH 255	/* random */

static DEFINE_MUTEX(chrdevs_lock);

static struct char_device_struct {
	struct char_device_struct *next;
	unsigned int major;
	unsigned int baseminor;
	int minorct;
	char name[64];
	struct file_operations *fops;
	struct cdev *cdev;		/* will die */
} *chrdevs[MAX_PROBE_HASH];

/* index in the above */
static inline int major_to_index(int major)
{
	return major % MAX_PROBE_HASH;
}

struct chrdev_info {
	int index;
	struct char_device_struct *cd;
};

void *get_next_chrdev(void *dev)
{
	struct chrdev_info *info;

	if (dev == NULL) {
		info = kmalloc(sizeof(*info), GFP_KERNEL);
		if (!info)
			goto out;
		info->index=0;
		info->cd = chrdevs[info->index];
		if (info->cd)
			goto out;
	} else {
		info = dev;
	}

	while (info->index < ARRAY_SIZE(chrdevs)) {
		if (info->cd)
			info->cd = info->cd->next;
		if (info->cd)
			goto out;
		/*
		 * No devices on this chain, move to the next
		 */
		info->index++;
		info->cd = (info->index < ARRAY_SIZE(chrdevs)) ?
			chrdevs[info->index] : NULL;
		if (info->cd)
			goto out;
	}

out:
	return info;
}

void *acquire_chrdev_list(void)
{
	mutex_lock(&chrdevs_lock);
	return get_next_chrdev(NULL);
}

void release_chrdev_list(void *dev)
{
	mutex_unlock(&chrdevs_lock);
	kfree(dev);
}


int count_chrdev_list(void)
{
	struct char_device_struct *cd;
	int i, count;

	count = 0;

	for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
		for (cd = chrdevs[i]; cd; cd = cd->next)
			count++;
	}

	return count;
}

int get_chrdev_info(void *dev, int *major, char **name)
{
	struct chrdev_info *info = dev;

	if (info->cd == NULL)
		return 1;

	*major = info->cd->major;
	*name = info->cd->name;
	return 0;
}

/*
 * Register a single major with a specified minor range.
 *
 * If major == 0 this functions will dynamically allocate a major and return
 * its number.
 *
 * If major > 0 this function will attempt to reserve the passed range of
 * minors and will return zero on success.
 *
 * Returns a -ve errno on failure.
 */
static struct char_device_struct *
__register_chrdev_region(unsigned int major, unsigned int baseminor,
			   int minorct, const char *name)
{
	struct char_device_struct *cd, **cp;
	int ret = 0;
	int i;

	cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
	if (cd == NULL)
		return ERR_PTR(-ENOMEM);

	memset(cd, 0, sizeof(struct char_device_struct));

	mutex_lock(&chrdevs_lock);

	/* temporary */
	if (major == 0) {
		for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
			if (chrdevs[i] == NULL)
				break;
		}

		if (i == 0) {
			ret = -EBUSY;
			goto out;
		}
		major = i;
		ret = major;
	}

	cd->major = major;
	cd->baseminor = baseminor;
	cd->minorct = minorct;
	strncpy(cd->name,name, 64);

	i = major_to_index(major);

	for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
		if ((*cp)->major > major ||
		    ((*cp)->major == major && (*cp)->baseminor >= baseminor))
			break;
	if (*cp && (*cp)->major == major &&
	    (*cp)->baseminor < baseminor + minorct) {
		ret = -EBUSY;
		goto out;
	}
	cd->next = *cp;
	*cp = cd;
	mutex_unlock(&chrdevs_lock);
	return cd;
out:
	mutex_unlock(&chrdevs_lock);
	kfree(cd);
	return ERR_PTR(ret);
}

static struct char_device_struct *
__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
{
	struct char_device_struct *cd = NULL, **cp;
	int i = major_to_index(major);

	mutex_lock(&chrdevs_lock);
	for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
		if ((*cp)->major == major &&
		    (*cp)->baseminor == baseminor &&
		    (*cp)->minorct == minorct)
			break;
	if (*cp) {
		cd = *cp;
		*cp = cd->next;
	}
	mutex_unlock(&chrdevs_lock);
	return cd;
}

int register_chrdev_region(dev_t from, unsigned count, const char *name)
{
	struct char_device_struct *cd;
	dev_t to = from + count;
	dev_t n, next;

	for (n = from; n < to; n = next) {
		next = MKDEV(MAJOR(n)+1, 0);
		if (next > to)
			next = to;
		cd = __register_chrdev_region(MAJOR(n), MINOR(n),
			       next - n, name);
		if (IS_ERR(cd))
			goto fail;
	}
	return 0;
fail:
	to = n;
	for (n = from; n < to; n = next) {
		next = MKDEV(MAJOR(n)+1, 0);
		kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	}
	return PTR_ERR(cd);
}

int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
			const char *name)
{
	struct char_device_struct *cd;
	cd = __register_chrdev_region(0, baseminor, count, name);
	if (IS_ERR(cd))
		return PTR_ERR(cd);
	*dev = MKDEV(cd->major, cd->baseminor);
	return 0;
}

int register_chrdev(unsigned int major, const char *name,
		    struct file_operations *fops)
{
	struct char_device_struct *cd;
	struct cdev *cdev;
	char *s;
	int err = -ENOMEM;

	cd = __register_chrdev_region(major, 0, 256, name);
	if (IS_ERR(cd))
		return PTR_ERR(cd);
	
	cdev = cdev_alloc();
	if (!cdev)
		goto out2;

	cdev->owner = fops->owner;
	cdev->ops = fops;
	kobject_set_name(&cdev->kobj, "%s", name);
	for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
		*s = '!';
		
	err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
	if (err)
		goto out;

	cd->cdev = cdev;

	return major ? 0 : cd->major;
out:
	kobject_put(&cdev->kobj);
out2:
	kfree(__unregister_chrdev_region(cd->major, 0, 256));
	return err;
}

void unregister_chrdev_region(dev_t from, unsigned count)
{
	dev_t to = from + count;
	dev_t n, next;

	for (n = from; n < to; n = next) {
		next = MKDEV(MAJOR(n)+1, 0);
		if (next > to)
			next = to;
		kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	}
}

int unregister_chrdev(unsigned int major, const char *name)
{
	struct char_device_struct *cd;
	cd = __unregister_chrdev_region(major, 0, 256);
	if (cd && cd->cdev)
		cdev_del(cd->cdev);
	kfree(cd);
	return 0;
}

static DEFINE_SPINLOCK(cdev_lock);

static struct kobject *cdev_get(struct cdev *p)
{
	struct module *owner = p->owner;
	struct kobject *kobj;

	if (owner && !try_module_get(owner))
		return NULL;
	kobj = kobject_get(&p->kobj);
	if (!kobj)
		module_put(owner);
	return kobj;
}

void cdev_put(struct cdev *p)
{
	if (p) {
		struct module *owner = p->owner;
		kobject_put(&p->kobj);
		module_put(owner);
	}
}

/*
 * Called every time a character special file is opened
 */
int chrdev_open(struct inode * inode, struct file * filp)
{
	struct cdev *p;
	struct cdev *new = NULL;
	int ret = 0;

	spin_lock(&cdev_lock);
	p = inode->i_cdev;
	if (!p) {
		struct kobject *kobj;
		int idx;
		spin_unlock(&cdev_lock);
		kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
		if (!kobj)
			return -ENXIO;
		new = container_of(kobj, struct cdev, kobj);
		spin_lock(&cdev_lock);
		p = inode->i_cdev;
		if (!p) {
			inode->i_cdev = p = new;
			inode->i_cindex = idx;
			list_add(&inode->i_devices, &p->list);
			new = NULL;
		} else if (!cdev_get(p))
			ret = -ENXIO;
	} else if (!cdev_get(p))
		ret = -ENXIO;
	spin_unlock(&cdev_lock);
	cdev_put(new);
	if (ret)
		return ret;
	filp->f_op = fops_get(p->ops);
	if (!filp->f_op) {
		cdev_put(p);
		return -ENXIO;
	}
	if (filp->f_op->open) {
		lock_kernel();
		ret = filp->f_op->open(inode,filp);
		unlock_kernel();
	}
	if (ret)
		cdev_put(p);
	return ret;
}

void cd_forget(struct inode *inode)
{
	spin_lock(&cdev_lock);
	list_del_init(&inode->i_devices);
	inode->i_cdev = NULL;
	spin_unlock(&cdev_lock);
}

static void cdev_purge(struct cdev *cdev)
{
	spin_lock(&cdev_lock);
	while (!list_empty(&cdev->list)) {
		struct inode *inode;
		inode = container_of(cdev->list.next, struct inode, i_devices);
		list_del_init(&inode->i_devices);
		inode->i_cdev = NULL;
	}
	spin_unlock(&cdev_lock);
}

/*
 * Dummy default file-operations: the only thing this does
 * is contain the open that then fills in the correct operations
 * depending on the special file...
 */
struct file_operations def_chr_fops = {
	.open = chrdev_open,
};

static struct kobject *exact_match(dev_t dev, int *part, void *data)
{
	struct cdev *p = data;
	return &p->kobj;
}

static int exact_lock(dev_t dev, void *data)
{
	struct cdev *p = data;
	return cdev_get(p) ? 0 : -1;
}

int cdev_add(struct cdev *p, dev_t dev, unsigned count)
{
	p->dev = dev;
	p->count = count;
	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
}

static void cdev_unmap(dev_t dev, unsigned count)
{
	kobj_unmap(cdev_map, dev, count);
}

void cdev_del(struct cdev *p)
{
	cdev_unmap(p->dev, p->count);
	kobject_put(&p->kobj);
}


static void cdev_default_release(struct kobject *kobj)
{
	struct cdev *p = container_of(kobj, struct cdev, kobj);
	cdev_purge(p);
}

static void cdev_dynamic_release(struct kobject *kobj)
{
	struct cdev *p = container_of(kobj, struct cdev, kobj);
	cdev_purge(p);
	kfree(p);
}

static struct kobj_type ktype_cdev_default = {
	.release	= cdev_default_release,
};

static struct kobj_type ktype_cdev_dynamic = {
	.release	= cdev_dynamic_release,
};

struct cdev *cdev_alloc(void)
{
	struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
	if (p) {
		memset(p, 0, sizeof(struct cdev));
		p->kobj.ktype = &ktype_cdev_dynamic;
		INIT_LIST_HEAD(&p->list);
		kobject_init(&p->kobj);
	}
	return p;
}

void cdev_init(struct cdev *cdev, struct file_operations *fops)
{
	memset(cdev, 0, sizeof *cdev);
	INIT_LIST_HEAD(&cdev->list);
	cdev->kobj.ktype = &ktype_cdev_default;
	kobject_init(&cdev->kobj);
	cdev->ops = fops;
}

static struct kobject *base_probe(dev_t dev, int *part, void *data)
{
	if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
		/* Make old-style 2.4 aliases work */
		request_module("char-major-%d", MAJOR(dev));
	return NULL;
}

void __init chrdev_init(void)
{
	cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
}


/* Let modules do char dev stuff */
EXPORT_SYMBOL(register_chrdev_region);
EXPORT_SYMBOL(unregister_chrdev_region);
EXPORT_SYMBOL(alloc_chrdev_region);
EXPORT_SYMBOL(cdev_init);
EXPORT_SYMBOL(cdev_alloc);
EXPORT_SYMBOL(cdev_del);
EXPORT_SYMBOL(cdev_add);
EXPORT_SYMBOL(register_chrdev);
EXPORT_SYMBOL(unregister_chrdev);
Commit	Line	Data
1da177e4 LT	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>
58383af6	22	#include <linux/mutex.h>
1da177e4 LT	23
	24	#ifdef CONFIG_KMOD
	25	#include <linux/kmod.h>
	26	#endif
	27
	28	static struct kobj_map *cdev_map;
	29
1d4d5b32	30	#define MAX_PROBE_HASH 255 /* random */
1da177e4	31
58383af6	32	static DEFINE_MUTEX(chrdevs_lock);
1da177e4 LT	33
	34	static struct char_device_struct {
	35	struct char_device_struct *next;
	36	unsigned int major;
	37	unsigned int baseminor;
	38	int minorct;
7170be5f	39	char name[64];
1da177e4 LT	40	struct file_operations *fops;
	41	struct cdev cdev; / will die */
	42	} *chrdevs[MAX_PROBE_HASH];
	43
	44	/* index in the above */
	45	static inline int major_to_index(int major)
	46	{
	47	return major % MAX_PROBE_HASH;
	48	}
	49
7170be5f NH	50	struct chrdev_info {
7170be5f NH	51	int index;
1da177e4	52	struct char_device_struct *cd;
7170be5f NH	53	};
	54
	55	void get_next_chrdev(void dev)
	56	{
	57	struct chrdev_info *info;
	58
	59	if (dev == NULL) {
	60	info = kmalloc(sizeof(*info), GFP_KERNEL);
	61	if (!info)
	62	goto out;
	63	info->index=0;
	64	info->cd = chrdevs[info->index];
	65	if (info->cd)
	66	goto out;
	67	} else {
	68	info = dev;
	69	}
	70
	71	while (info->index < ARRAY_SIZE(chrdevs)) {
	72	if (info->cd)
	73	info->cd = info->cd->next;
	74	if (info->cd)
	75	goto out;
	76	/*
	77	* No devices on this chain, move to the next
	78	*/
	79	info->index++;
	80	info->cd = (info->index < ARRAY_SIZE(chrdevs)) ?
	81	chrdevs[info->index] : NULL;
	82	if (info->cd)
	83	goto out;
	84	}
1da177e4	85
7170be5f NH	86	out:
	87	return info;
	88	}
1da177e4	89
7170be5f NH	90	void *acquire_chrdev_list(void)
7170be5f NH	91	{
58383af6	92	mutex_lock(&chrdevs_lock);
7170be5f NH	93	return get_next_chrdev(NULL);
	94	}
	95
	96	void release_chrdev_list(void *dev)
	97	{
58383af6	98	mutex_unlock(&chrdevs_lock);
7170be5f NH	99	kfree(dev);
	100	}
	101
	102
	103	int count_chrdev_list(void)
	104	{
	105	struct char_device_struct *cd;
	106	int i, count;
	107
	108	count = 0;
	109
1da177e4	110	for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
7170be5f NH	111	for (cd = chrdevs[i]; cd; cd = cd->next)
7170be5f NH	112	count++;
1da177e4	113	}
1da177e4	114
7170be5f NH	115	return count;
	116	}
	117
	118	int get_chrdev_info(void dev, int major, char **name)
	119	{
	120	struct chrdev_info *info = dev;
	121
	122	if (info->cd == NULL)
	123	return 1;
	124
	125	*major = info->cd->major;
	126	*name = info->cd->name;
	127	return 0;
1da177e4 LT	128	}
	129
	130	/*
	131	* Register a single major with a specified minor range.
	132	*
	133	* If major == 0 this functions will dynamically allocate a major and return
	134	* its number.
	135	*
	136	* If major > 0 this function will attempt to reserve the passed range of
	137	* minors and will return zero on success.
	138	*
	139	* Returns a -ve errno on failure.
	140	*/
	141	static struct char_device_struct *
	142	__register_chrdev_region(unsigned int major, unsigned int baseminor,
	143	int minorct, const char *name)
	144	{
	145	struct char_device_struct cd, *cp;
	146	int ret = 0;
	147	int i;
	148
	149	cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
	150	if (cd == NULL)
	151	return ERR_PTR(-ENOMEM);
	152
	153	memset(cd, 0, sizeof(struct char_device_struct));
	154
58383af6	155	mutex_lock(&chrdevs_lock);
1da177e4 LT	156
	157	/* temporary */
	158	if (major == 0) {
	159	for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
	160	if (chrdevs[i] == NULL)
	161	break;
	162	}
	163
	164	if (i == 0) {
	165	ret = -EBUSY;
	166	goto out;
	167	}
	168	major = i;
	169	ret = major;
	170	}
	171
	172	cd->major = major;
	173	cd->baseminor = baseminor;
	174	cd->minorct = minorct;
7170be5f	175	strncpy(cd->name,name, 64);
1da177e4 LT	176
	177	i = major_to_index(major);
	178
	179	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	180	if ((*cp)->major > major \|\|
	181	((cp)->major == major && (cp)->baseminor >= baseminor))
	182	break;
	183	if (cp && (cp)->major == major &&
	184	(*cp)->baseminor < baseminor + minorct) {
	185	ret = -EBUSY;
	186	goto out;
	187	}
	188	cd->next = *cp;
	189	*cp = cd;
58383af6	190	mutex_unlock(&chrdevs_lock);
1da177e4 LT	191	return cd;
1da177e4 LT	192	out:
58383af6	193	mutex_unlock(&chrdevs_lock);
1da177e4 LT	194	kfree(cd);
	195	return ERR_PTR(ret);
	196	}
	197
	198	static struct char_device_struct *
	199	__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
	200	{
	201	struct char_device_struct cd = NULL, *cp;
	202	int i = major_to_index(major);
	203
58383af6	204	mutex_lock(&chrdevs_lock);
1da177e4 LT	205	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	206	if ((*cp)->major == major &&
	207	(*cp)->baseminor == baseminor &&
	208	(*cp)->minorct == minorct)
	209	break;
	210	if (*cp) {
	211	cd = *cp;
	212	*cp = cd->next;
	213	}
58383af6	214	mutex_unlock(&chrdevs_lock);
1da177e4 LT	215	return cd;
	216	}
	217
	218	int register_chrdev_region(dev_t from, unsigned count, const char *name)
	219	{
	220	struct char_device_struct *cd;
	221	dev_t to = from + count;
	222	dev_t n, next;
	223
	224	for (n = from; n < to; n = next) {
	225	next = MKDEV(MAJOR(n)+1, 0);
	226	if (next > to)
	227	next = to;
	228	cd = __register_chrdev_region(MAJOR(n), MINOR(n),
	229	next - n, name);
	230	if (IS_ERR(cd))
	231	goto fail;
	232	}
	233	return 0;
	234	fail:
	235	to = n;
	236	for (n = from; n < to; n = next) {
	237	next = MKDEV(MAJOR(n)+1, 0);
	238	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	239	}
	240	return PTR_ERR(cd);
	241	}
	242
	243	int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
	244	const char *name)
	245	{
	246	struct char_device_struct *cd;
	247	cd = __register_chrdev_region(0, baseminor, count, name);
	248	if (IS_ERR(cd))
	249	return PTR_ERR(cd);
	250	*dev = MKDEV(cd->major, cd->baseminor);
	251	return 0;
	252	}
	253
	254	int register_chrdev(unsigned int major, const char *name,
	255	struct file_operations *fops)
	256	{
	257	struct char_device_struct *cd;
	258	struct cdev *cdev;
	259	char *s;
	260	int err = -ENOMEM;
	261
	262	cd = __register_chrdev_region(major, 0, 256, name);
	263	if (IS_ERR(cd))
	264	return PTR_ERR(cd);
	265
	266	cdev = cdev_alloc();
	267	if (!cdev)
	268	goto out2;
	269
	270	cdev->owner = fops->owner;
	271	cdev->ops = fops;
	272	kobject_set_name(&cdev->kobj, "%s", name);
	273	for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
	274	*s = '!';
	275
	276	err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
	277	if (err)
	278	goto out;
279
280	cd->cdev = cdev;
281
282	return major ? 0 : cd->major;
283	out:
284	kobject_put(&cdev->kobj);
285	out2:
286	kfree(__unregister_chrdev_region(cd->major, 0, 256));
287	return err;
288	}
289
290	void unregister_chrdev_region(dev_t from, unsigned count)
291	{
292	dev_t to = from + count;
293	dev_t n, next;
294
295	for (n = from; n < to; n = next) {
296	next = MKDEV(MAJOR(n)+1, 0);
297	if (next > to)
298	next = to;
299	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
300	}
301	}
302
303	int unregister_chrdev(unsigned int major, const char *name)
304	{
305	struct char_device_struct *cd;
306	cd = __unregister_chrdev_region(major, 0, 256);
307	if (cd && cd->cdev)
308	cdev_del(cd->cdev);
309	kfree(cd);
310	return 0;
311	}
312
313	static DEFINE_SPINLOCK(cdev_lock);
314
315	static struct kobject cdev_get(struct cdev p)
316	{
317	struct module *owner = p->owner;
318	struct kobject *kobj;
319
320	if (owner && !try_module_get(owner))
321	return NULL;
322	kobj = kobject_get(&p->kobj);
323	if (!kobj)
324	module_put(owner);
325	return kobj;
326	}
327
328	void cdev_put(struct cdev *p)
329	{
330	if (p) {
7da6844c	331	struct module *owner = p->owner;
1da177e4	332	kobject_put(&p->kobj);
7da6844c	333	module_put(owner);
1da177e4 LT	334	}
	335	}
	336
	337	/*
	338	* Called every time a character special file is opened
	339	*/
	340	int chrdev_open(struct inode * inode, struct file * filp)
	341	{
	342	struct cdev *p;
	343	struct cdev *new = NULL;
	344	int ret = 0;
	345
	346	spin_lock(&cdev_lock);
	347	p = inode->i_cdev;
	348	if (!p) {
	349	struct kobject *kobj;
	350	int idx;
	351	spin_unlock(&cdev_lock);
	352	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	353	if (!kobj)
	354	return -ENXIO;
	355	new = container_of(kobj, struct cdev, kobj);
	356	spin_lock(&cdev_lock);
	357	p = inode->i_cdev;
	358	if (!p) {
	359	inode->i_cdev = p = new;
	360	inode->i_cindex = idx;
	361	list_add(&inode->i_devices, &p->list);
	362	new = NULL;
	363	} else if (!cdev_get(p))
	364	ret = -ENXIO;
	365	} else if (!cdev_get(p))
	366	ret = -ENXIO;
	367	spin_unlock(&cdev_lock);
	368	cdev_put(new);
	369	if (ret)
	370	return ret;
	371	filp->f_op = fops_get(p->ops);
	372	if (!filp->f_op) {
	373	cdev_put(p);
	374	return -ENXIO;
	375	}
	376	if (filp->f_op->open) {
	377	lock_kernel();
	378	ret = filp->f_op->open(inode,filp);
	379	unlock_kernel();
	380	}
	381	if (ret)
	382	cdev_put(p);
	383	return ret;
	384	}
	385
	386	void cd_forget(struct inode *inode)
	387	{
	388	spin_lock(&cdev_lock);
	389	list_del_init(&inode->i_devices);
	390	inode->i_cdev = NULL;
	391	spin_unlock(&cdev_lock);
	392	}
	393
75c96f85	394	static void cdev_purge(struct cdev *cdev)
1da177e4 LT	395	{
	396	spin_lock(&cdev_lock);
	397	while (!list_empty(&cdev->list)) {
	398	struct inode *inode;
	399	inode = container_of(cdev->list.next, struct inode, i_devices);
	400	list_del_init(&inode->i_devices);
	401	inode->i_cdev = NULL;
	402	}
	403	spin_unlock(&cdev_lock);
	404	}
	405
	406	/*
	407	* Dummy default file-operations: the only thing this does
	408	* is contain the open that then fills in the correct operations
	409	* depending on the special file...
	410	*/
	411	struct file_operations def_chr_fops = {
	412	.open = chrdev_open,
	413	};
	414
	415	static struct kobject exact_match(dev_t dev, int part, void *data)
	416	{
	417	struct cdev *p = data;
	418	return &p->kobj;
	419	}
	420
	421	static int exact_lock(dev_t dev, void *data)
	422	{
	423	struct cdev *p = data;
	424	return cdev_get(p) ? 0 : -1;
	425	}
	426
	427	int cdev_add(struct cdev *p, dev_t dev, unsigned count)
	428	{
	429	p->dev = dev;
	430	p->count = count;
	431	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
	432	}
	433
	434	static void cdev_unmap(dev_t dev, unsigned count)
	435	{
	436	kobj_unmap(cdev_map, dev, count);
	437	}
	438
	439	void cdev_del(struct cdev *p)
	440	{
	441	cdev_unmap(p->dev, p->count);
	442	kobject_put(&p->kobj);
	443	}
	444
	445
	446	static void cdev_default_release(struct kobject *kobj)
	447	{
	448	struct cdev *p = container_of(kobj, struct cdev, kobj);
	449	cdev_purge(p);
	450	}
	451
	452	static void cdev_dynamic_release(struct kobject *kobj)
	453	{
	454	struct cdev *p = container_of(kobj, struct cdev, kobj);
	455	cdev_purge(p);
	456	kfree(p);
	457	}
	458
459	static struct kobj_type ktype_cdev_default = {
460	.release = cdev_default_release,
461	};
462
463	static struct kobj_type ktype_cdev_dynamic = {
464	.release = cdev_dynamic_release,
465	};
466
467	struct cdev *cdev_alloc(void)
468	{
469	struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
470	if (p) {
471	memset(p, 0, sizeof(struct cdev));
472	p->kobj.ktype = &ktype_cdev_dynamic;
473	INIT_LIST_HEAD(&p->list);
474	kobject_init(&p->kobj);
475	}
476	return p;
477	}
478
479	void cdev_init(struct cdev cdev, struct file_operations fops)
480	{
481	memset(cdev, 0, sizeof *cdev);
482	INIT_LIST_HEAD(&cdev->list);
483	cdev->kobj.ktype = &ktype_cdev_default;
484	kobject_init(&cdev->kobj);
485	cdev->ops = fops;
486	}
487
488	static struct kobject base_probe(dev_t dev, int part, void *data)
489	{
490	if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
491	/* Make old-style 2.4 aliases work */
492	request_module("char-major-%d", MAJOR(dev));
493	return NULL;
494	}
495
496	void __init chrdev_init(void)
497	{
498	cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
499	}
500
501
502	/* Let modules do char dev stuff */
503	EXPORT_SYMBOL(register_chrdev_region);
504	EXPORT_SYMBOL(unregister_chrdev_region);
505	EXPORT_SYMBOL(alloc_chrdev_region);
506	EXPORT_SYMBOL(cdev_init);
507	EXPORT_SYMBOL(cdev_alloc);
508	EXPORT_SYMBOL(cdev_del);
509	EXPORT_SYMBOL(cdev_add);
510	EXPORT_SYMBOL(register_chrdev);
511	EXPORT_SYMBOL(unregister_chrdev);