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

	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,
		    const 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 = kzalloc(sizeof(struct cdev), GFP_KERNEL);
	if (p) {
		p->kobj.ktype = &ktype_cdev_dynamic;
		INIT_LIST_HEAD(&p->list);
		kobject_init(&p->kobj);
	}
	return p;
}

void cdev_init(struct cdev *cdev, const 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
11b0b5ab	149	cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
1da177e4 LT	150	if (cd == NULL)
	151	return ERR_PTR(-ENOMEM);
	152
58383af6	153	mutex_lock(&chrdevs_lock);
1da177e4 LT	154
	155	/* temporary */
	156	if (major == 0) {
	157	for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
	158	if (chrdevs[i] == NULL)
	159	break;
	160	}
	161
	162	if (i == 0) {
	163	ret = -EBUSY;
	164	goto out;
	165	}
	166	major = i;
	167	ret = major;
	168	}
	169
	170	cd->major = major;
	171	cd->baseminor = baseminor;
	172	cd->minorct = minorct;
7170be5f	173	strncpy(cd->name,name, 64);
1da177e4 LT	174
	175	i = major_to_index(major);
	176
	177	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	178	if ((*cp)->major > major \|\|
	179	((cp)->major == major && (cp)->baseminor >= baseminor))
	180	break;
	181	if (cp && (cp)->major == major &&
	182	(*cp)->baseminor < baseminor + minorct) {
	183	ret = -EBUSY;
	184	goto out;
	185	}
	186	cd->next = *cp;
	187	*cp = cd;
58383af6	188	mutex_unlock(&chrdevs_lock);
1da177e4 LT	189	return cd;
1da177e4 LT	190	out:
58383af6	191	mutex_unlock(&chrdevs_lock);
1da177e4 LT	192	kfree(cd);
	193	return ERR_PTR(ret);
	194	}
	195
	196	static struct char_device_struct *
	197	__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
	198	{
	199	struct char_device_struct cd = NULL, *cp;
	200	int i = major_to_index(major);
	201
58383af6	202	mutex_lock(&chrdevs_lock);
1da177e4 LT	203	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	204	if ((*cp)->major == major &&
	205	(*cp)->baseminor == baseminor &&
	206	(*cp)->minorct == minorct)
	207	break;
	208	if (*cp) {
	209	cd = *cp;
	210	*cp = cd->next;
	211	}
58383af6	212	mutex_unlock(&chrdevs_lock);
1da177e4 LT	213	return cd;
	214	}
	215
	216	int register_chrdev_region(dev_t from, unsigned count, const char *name)
	217	{
	218	struct char_device_struct *cd;
	219	dev_t to = from + count;
	220	dev_t n, next;
	221
	222	for (n = from; n < to; n = next) {
	223	next = MKDEV(MAJOR(n)+1, 0);
	224	if (next > to)
	225	next = to;
	226	cd = __register_chrdev_region(MAJOR(n), MINOR(n),
	227	next - n, name);
	228	if (IS_ERR(cd))
	229	goto fail;
	230	}
	231	return 0;
	232	fail:
	233	to = n;
	234	for (n = from; n < to; n = next) {
	235	next = MKDEV(MAJOR(n)+1, 0);
	236	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	237	}
	238	return PTR_ERR(cd);
	239	}
	240
	241	int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
	242	const char *name)
	243	{
	244	struct char_device_struct *cd;
	245	cd = __register_chrdev_region(0, baseminor, count, name);
	246	if (IS_ERR(cd))
	247	return PTR_ERR(cd);
	248	*dev = MKDEV(cd->major, cd->baseminor);
	249	return 0;
	250	}
	251
	252	int register_chrdev(unsigned int major, const char *name,
99ac48f5	253	const struct file_operations *fops)
1da177e4 LT	254	{
	255	struct char_device_struct *cd;
	256	struct cdev *cdev;
	257	char *s;
	258	int err = -ENOMEM;
	259
	260	cd = __register_chrdev_region(major, 0, 256, name);
	261	if (IS_ERR(cd))
	262	return PTR_ERR(cd);
	263
	264	cdev = cdev_alloc();
	265	if (!cdev)
	266	goto out2;
	267
	268	cdev->owner = fops->owner;
	269	cdev->ops = fops;
	270	kobject_set_name(&cdev->kobj, "%s", name);
	271	for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
	272	*s = '!';
	273
	274	err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
	275	if (err)
	276	goto out;
	277
	278	cd->cdev = cdev;
	279
	280	return major ? 0 : cd->major;
	281	out:
	282	kobject_put(&cdev->kobj);
	283	out2:
	284	kfree(__unregister_chrdev_region(cd->major, 0, 256));
	285	return err;
	286	}
	287
	288	void unregister_chrdev_region(dev_t from, unsigned count)
	289	{
	290	dev_t to = from + count;
	291	dev_t n, next;
	292
	293	for (n = from; n < to; n = next) {
	294	next = MKDEV(MAJOR(n)+1, 0);
	295	if (next > to)
	296	next = to;
	297	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	298	}
	299	}
	300
	301	int unregister_chrdev(unsigned int major, const char *name)
	302	{
	303	struct char_device_struct *cd;
	304	cd = __unregister_chrdev_region(major, 0, 256);
	305	if (cd && cd->cdev)
	306	cdev_del(cd->cdev);
	307	kfree(cd);
	308	return 0;
	309	}
	310
	311	static DEFINE_SPINLOCK(cdev_lock);
	312
	313	static struct kobject cdev_get(struct cdev p)
	314	{
	315	struct module *owner = p->owner;
	316	struct kobject *kobj;
	317
318	if (owner && !try_module_get(owner))
319	return NULL;
320	kobj = kobject_get(&p->kobj);
321	if (!kobj)
322	module_put(owner);
323	return kobj;
324	}
325
326	void cdev_put(struct cdev *p)
327	{
328	if (p) {
7da6844c	329	struct module *owner = p->owner;
1da177e4	330	kobject_put(&p->kobj);
7da6844c	331	module_put(owner);
1da177e4 LT	332	}
	333	}
	334
	335	/*
	336	* Called every time a character special file is opened
	337	*/
	338	int chrdev_open(struct inode * inode, struct file * filp)
	339	{
	340	struct cdev *p;
	341	struct cdev *new = NULL;
	342	int ret = 0;
	343
	344	spin_lock(&cdev_lock);
	345	p = inode->i_cdev;
	346	if (!p) {
	347	struct kobject *kobj;
	348	int idx;
	349	spin_unlock(&cdev_lock);
	350	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	351	if (!kobj)
	352	return -ENXIO;
	353	new = container_of(kobj, struct cdev, kobj);
	354	spin_lock(&cdev_lock);
	355	p = inode->i_cdev;
	356	if (!p) {
	357	inode->i_cdev = p = new;
	358	inode->i_cindex = idx;
	359	list_add(&inode->i_devices, &p->list);
	360	new = NULL;
	361	} else if (!cdev_get(p))
	362	ret = -ENXIO;
	363	} else if (!cdev_get(p))
	364	ret = -ENXIO;
	365	spin_unlock(&cdev_lock);
	366	cdev_put(new);
	367	if (ret)
	368	return ret;
	369	filp->f_op = fops_get(p->ops);
	370	if (!filp->f_op) {
	371	cdev_put(p);
	372	return -ENXIO;
	373	}
	374	if (filp->f_op->open) {
	375	lock_kernel();
	376	ret = filp->f_op->open(inode,filp);
	377	unlock_kernel();
	378	}
	379	if (ret)
	380	cdev_put(p);
	381	return ret;
	382	}
	383
	384	void cd_forget(struct inode *inode)
	385	{
	386	spin_lock(&cdev_lock);
	387	list_del_init(&inode->i_devices);
	388	inode->i_cdev = NULL;
	389	spin_unlock(&cdev_lock);
	390	}
	391
75c96f85	392	static void cdev_purge(struct cdev *cdev)
1da177e4 LT	393	{
	394	spin_lock(&cdev_lock);
	395	while (!list_empty(&cdev->list)) {
	396	struct inode *inode;
	397	inode = container_of(cdev->list.next, struct inode, i_devices);
	398	list_del_init(&inode->i_devices);
	399	inode->i_cdev = NULL;
	400	}
	401	spin_unlock(&cdev_lock);
	402	}
	403
	404	/*
	405	* Dummy default file-operations: the only thing this does
	406	* is contain the open that then fills in the correct operations
	407	* depending on the special file...
	408	*/
	409	struct file_operations def_chr_fops = {
	410	.open = chrdev_open,
	411	};
	412
	413	static struct kobject exact_match(dev_t dev, int part, void *data)
	414	{
	415	struct cdev *p = data;
	416	return &p->kobj;
	417	}
	418
	419	static int exact_lock(dev_t dev, void *data)
	420	{
	421	struct cdev *p = data;
	422	return cdev_get(p) ? 0 : -1;
	423	}
	424
	425	int cdev_add(struct cdev *p, dev_t dev, unsigned count)
	426	{
	427	p->dev = dev;
	428	p->count = count;
	429	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
	430	}
	431
	432	static void cdev_unmap(dev_t dev, unsigned count)
	433	{
	434	kobj_unmap(cdev_map, dev, count);
	435	}
	436
	437	void cdev_del(struct cdev *p)
	438	{
	439	cdev_unmap(p->dev, p->count);
	440	kobject_put(&p->kobj);
	441	}
	442
	443
	444	static void cdev_default_release(struct kobject *kobj)
	445	{
	446	struct cdev *p = container_of(kobj, struct cdev, kobj);
	447	cdev_purge(p);
	448	}
	449
	450	static void cdev_dynamic_release(struct kobject *kobj)
	451	{
	452	struct cdev *p = container_of(kobj, struct cdev, kobj);
	453	cdev_purge(p);
	454	kfree(p);
	455	}
	456
457	static struct kobj_type ktype_cdev_default = {
458	.release = cdev_default_release,
459	};
460
461	static struct kobj_type ktype_cdev_dynamic = {
462	.release = cdev_dynamic_release,
463	};
464
465	struct cdev *cdev_alloc(void)
466	{
11b0b5ab	467	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
1da177e4	468	if (p) {
1da177e4 LT	469	p->kobj.ktype = &ktype_cdev_dynamic;
	470	INIT_LIST_HEAD(&p->list);
	471	kobject_init(&p->kobj);
	472	}
	473	return p;
	474	}
	475
99ac48f5	476	void cdev_init(struct cdev cdev, const struct file_operations fops)
1da177e4 LT	477	{
	478	memset(cdev, 0, sizeof *cdev);
	479	INIT_LIST_HEAD(&cdev->list);
	480	cdev->kobj.ktype = &ktype_cdev_default;
	481	kobject_init(&cdev->kobj);
	482	cdev->ops = fops;
	483	}
	484
	485	static struct kobject base_probe(dev_t dev, int part, void *data)
	486	{
	487	if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
	488	/* Make old-style 2.4 aliases work */
	489	request_module("char-major-%d", MAJOR(dev));
	490	return NULL;
	491	}
	492
	493	void __init chrdev_init(void)
	494	{
	495	cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
	496	}
	497
	498
	499	/* Let modules do char dev stuff */
	500	EXPORT_SYMBOL(register_chrdev_region);
	501	EXPORT_SYMBOL(unregister_chrdev_region);
	502	EXPORT_SYMBOL(alloc_chrdev_region);
	503	EXPORT_SYMBOL(cdev_init);
	504	EXPORT_SYMBOL(cdev_alloc);
	505	EXPORT_SYMBOL(cdev_del);
	506	EXPORT_SYMBOL(cdev_add);
	507	EXPORT_SYMBOL(register_chrdev);
	508	EXPORT_SYMBOL(unregister_chrdev);