[mirror_ubuntu-artful-kernel.git] / fs / char_dev.c

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

#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/seq_file.h>

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

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

/*
 * capabilities for /dev/mem, /dev/kmem and similar directly mappable character
 * devices
 * - permits shared-mmap for read, write and/or exec
 * - does not permit private mmap in NOMMU mode (can't do COW)
 * - no readahead or I/O queue unplugging required
 */
struct backing_dev_info directly_mappable_cdev_bdi = {
	.capabilities	= (
#ifdef CONFIG_MMU
		/* permit private copies of the data to be taken */
		BDI_CAP_MAP_COPY |
#endif
		/* permit direct mmap, for read, write or exec */
		BDI_CAP_MAP_DIRECT |
		BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),
};

static struct kobj_map *cdev_map;

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[CHRDEV_MAJOR_HASH_SIZE];

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

#ifdef CONFIG_PROC_FS

void chrdev_show(struct seq_file *f, off_t offset)
{
	struct char_device_struct *cd;

	if (offset < CHRDEV_MAJOR_HASH_SIZE) {
		mutex_lock(&chrdevs_lock);
		for (cd = chrdevs[offset]; cd; cd = cd->next)
			seq_printf(f, "%3d %s\n", cd->major, cd->name);
		mutex_unlock(&chrdevs_lock);
	}
}

#endif /* CONFIG_PROC_FS */

/*
 * 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) ||
		      ((*cp)->baseminor + (*cp)->minorct > baseminor))))
			break;

	/* Check for overlapping minor ranges.  */
	if (*cp && (*cp)->major == major) {
		int old_min = (*cp)->baseminor;
		int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
		int new_min = baseminor;
		int new_max = baseminor + minorct - 1;

		/* New driver overlaps from the left.  */
		if (new_max >= old_min && new_max <= old_max) {
			ret = -EBUSY;
			goto out;
		}

		/* New driver overlaps from the right.  */
		if (new_min <= old_max && new_min >= old_min) {
			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;
}

/**
 * register_chrdev() - Register a major number for character devices.
 * @major: major device number or 0 for dynamic allocation
 * @name: name of this range of devices
 * @fops: file operations associated with this devices
 *
 * If @major == 0 this functions will dynamically allocate a major and return
 * its number.
 *
 * If @major > 0 this function will attempt to reserve a device with the given
 * major number and will return zero on success.
 *
 * Returns a -ve errno on failure.
 *
 * The name of this device has nothing to do with the name of the device in
 * /dev. It only helps to keep track of the different owners of devices. If
 * your module name has only one type of devices it's ok to use e.g. the name
 * of the module here.
 *
 * This function registers a range of 256 minor numbers. The first minor number
 * is 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...
 */
const 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);
EXPORT_SYMBOL(directly_mappable_cdev_bdi);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/char_dev.c
	3	*
	4	* Copyright (C) 1991, 1992 Linus Torvalds
	5	*/
	6
1da177e4 LT	7	#include <linux/init.h>
	8	#include <linux/fs.h>
	9	#include <linux/slab.h>
	10	#include <linux/string.h>
	11
	12	#include <linux/major.h>
	13	#include <linux/errno.h>
	14	#include <linux/module.h>
	15	#include <linux/smp_lock.h>
68eef3b4	16	#include <linux/seq_file.h>
1da177e4 LT	17
	18	#include <linux/kobject.h>
	19	#include <linux/kobj_map.h>
	20	#include <linux/cdev.h>
58383af6	21	#include <linux/mutex.h>
5da6185b	22	#include <linux/backing-dev.h>
1da177e4 LT	23
	24	#ifdef CONFIG_KMOD
	25	#include <linux/kmod.h>
	26	#endif
	27
5da6185b DH	28	/*
	29	* capabilities for /dev/mem, /dev/kmem and similar directly mappable character
	30	* devices
	31	* - permits shared-mmap for read, write and/or exec
	32	* - does not permit private mmap in NOMMU mode (can't do COW)
	33	* - no readahead or I/O queue unplugging required
	34	*/
	35	struct backing_dev_info directly_mappable_cdev_bdi = {
	36	.capabilities = (
	37	#ifdef CONFIG_MMU
	38	/* permit private copies of the data to be taken */
	39	BDI_CAP_MAP_COPY \|
	40	#endif
	41	/* permit direct mmap, for read, write or exec */
	42	BDI_CAP_MAP_DIRECT \|
	43	BDI_CAP_READ_MAP \| BDI_CAP_WRITE_MAP \| BDI_CAP_EXEC_MAP),
	44	};
	45
1da177e4 LT	46	static struct kobj_map *cdev_map;
1da177e4 LT	47
58383af6	48	static DEFINE_MUTEX(chrdevs_lock);
1da177e4 LT	49
	50	static struct char_device_struct {
	51	struct char_device_struct *next;
	52	unsigned int major;
	53	unsigned int baseminor;
	54	int minorct;
7170be5f	55	char name[64];
1da177e4 LT	56	struct file_operations *fops;
1da177e4 LT	57	struct cdev cdev; / will die */
68eef3b4	58	} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
1da177e4 LT	59
	60	/* index in the above */
	61	static inline int major_to_index(int major)
	62	{
68eef3b4	63	return major % CHRDEV_MAJOR_HASH_SIZE;
7170be5f NH	64	}
7170be5f NH	65
68eef3b4	66	#ifdef CONFIG_PROC_FS
7170be5f	67
68eef3b4	68	void chrdev_show(struct seq_file *f, off_t offset)
7170be5f NH	69	{
7170be5f NH	70	struct char_device_struct *cd;
7170be5f	71
68eef3b4 JK	72	if (offset < CHRDEV_MAJOR_HASH_SIZE) {
	73	mutex_lock(&chrdevs_lock);
	74	for (cd = chrdevs[offset]; cd; cd = cd->next)
	75	seq_printf(f, "%3d %s\n", cd->major, cd->name);
	76	mutex_unlock(&chrdevs_lock);
1da177e4	77	}
7170be5f NH	78	}
7170be5f NH	79
68eef3b4	80	#endif /* CONFIG_PROC_FS */
1da177e4 LT	81
	82	/*
	83	* Register a single major with a specified minor range.
	84	*
	85	* If major == 0 this functions will dynamically allocate a major and return
	86	* its number.
	87	*
	88	* If major > 0 this function will attempt to reserve the passed range of
	89	* minors and will return zero on success.
	90	*
	91	* Returns a -ve errno on failure.
	92	*/
	93	static struct char_device_struct *
	94	__register_chrdev_region(unsigned int major, unsigned int baseminor,
	95	int minorct, const char *name)
	96	{
	97	struct char_device_struct cd, *cp;
	98	int ret = 0;
	99	int i;
	100
11b0b5ab	101	cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
1da177e4 LT	102	if (cd == NULL)
	103	return ERR_PTR(-ENOMEM);
	104
58383af6	105	mutex_lock(&chrdevs_lock);
1da177e4 LT	106
	107	/* temporary */
	108	if (major == 0) {
	109	for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
	110	if (chrdevs[i] == NULL)
	111	break;
	112	}
	113
	114	if (i == 0) {
	115	ret = -EBUSY;
	116	goto out;
	117	}
	118	major = i;
	119	ret = major;
	120	}
	121
	122	cd->major = major;
	123	cd->baseminor = baseminor;
	124	cd->minorct = minorct;
7170be5f	125	strncpy(cd->name,name, 64);
1da177e4 LT	126
	127	i = major_to_index(major);
	128
	129	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	130	if ((*cp)->major > major \|\|
01d553d0 AW	131	((*cp)->major == major &&
	132	(((*cp)->baseminor >= baseminor) \|\|
	133	((cp)->baseminor + (cp)->minorct > baseminor))))
1da177e4	134	break;
01d553d0 AW	135
	136	/* Check for overlapping minor ranges. */
	137	if (cp && (cp)->major == major) {
	138	int old_min = (*cp)->baseminor;
	139	int old_max = (cp)->baseminor + (cp)->minorct - 1;
	140	int new_min = baseminor;
	141	int new_max = baseminor + minorct - 1;
	142
	143	/* New driver overlaps from the left. */
	144	if (new_max >= old_min && new_max <= old_max) {
	145	ret = -EBUSY;
	146	goto out;
	147	}
	148
	149	/* New driver overlaps from the right. */
	150	if (new_min <= old_max && new_min >= old_min) {
	151	ret = -EBUSY;
	152	goto out;
	153	}
1da177e4	154	}
01d553d0	155
1da177e4 LT	156	cd->next = *cp;
1da177e4 LT	157	*cp = cd;
58383af6	158	mutex_unlock(&chrdevs_lock);
1da177e4 LT	159	return cd;
1da177e4 LT	160	out:
58383af6	161	mutex_unlock(&chrdevs_lock);
1da177e4 LT	162	kfree(cd);
	163	return ERR_PTR(ret);
	164	}
	165
	166	static struct char_device_struct *
	167	__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
	168	{
	169	struct char_device_struct cd = NULL, *cp;
	170	int i = major_to_index(major);
	171
58383af6	172	mutex_lock(&chrdevs_lock);
1da177e4 LT	173	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	174	if ((*cp)->major == major &&
	175	(*cp)->baseminor == baseminor &&
	176	(*cp)->minorct == minorct)
	177	break;
	178	if (*cp) {
	179	cd = *cp;
	180	*cp = cd->next;
	181	}
58383af6	182	mutex_unlock(&chrdevs_lock);
1da177e4 LT	183	return cd;
	184	}
	185
	186	int register_chrdev_region(dev_t from, unsigned count, const char *name)
	187	{
	188	struct char_device_struct *cd;
	189	dev_t to = from + count;
	190	dev_t n, next;
	191
	192	for (n = from; n < to; n = next) {
	193	next = MKDEV(MAJOR(n)+1, 0);
	194	if (next > to)
	195	next = to;
	196	cd = __register_chrdev_region(MAJOR(n), MINOR(n),
	197	next - n, name);
	198	if (IS_ERR(cd))
	199	goto fail;
	200	}
	201	return 0;
	202	fail:
	203	to = n;
	204	for (n = from; n < to; n = next) {
	205	next = MKDEV(MAJOR(n)+1, 0);
	206	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	207	}
	208	return PTR_ERR(cd);
	209	}
	210
	211	int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
	212	const char *name)
	213	{
	214	struct char_device_struct *cd;
	215	cd = __register_chrdev_region(0, baseminor, count, name);
	216	if (IS_ERR(cd))
	217	return PTR_ERR(cd);
	218	*dev = MKDEV(cd->major, cd->baseminor);
	219	return 0;
	220	}
	221
d247e2c6 REB	222	/**
	223	* register_chrdev() - Register a major number for character devices.
	224	* @major: major device number or 0 for dynamic allocation
	225	* @name: name of this range of devices
	226	* @fops: file operations associated with this devices
	227	*
	228	* If @major == 0 this functions will dynamically allocate a major and return
	229	* its number.
	230	*
	231	* If @major > 0 this function will attempt to reserve a device with the given
	232	* major number and will return zero on success.
	233	*
	234	* Returns a -ve errno on failure.
	235	*
	236	* The name of this device has nothing to do with the name of the device in
	237	* /dev. It only helps to keep track of the different owners of devices. If
	238	* your module name has only one type of devices it's ok to use e.g. the name
	239	* of the module here.
	240	*
	241	* This function registers a range of 256 minor numbers. The first minor number
	242	* is 0.
	243	*/
1da177e4	244	int register_chrdev(unsigned int major, const char *name,
99ac48f5	245	const struct file_operations *fops)
1da177e4 LT	246	{
	247	struct char_device_struct *cd;
	248	struct cdev *cdev;
	249	char *s;
	250	int err = -ENOMEM;
	251
	252	cd = __register_chrdev_region(major, 0, 256, name);
	253	if (IS_ERR(cd))
	254	return PTR_ERR(cd);
	255
	256	cdev = cdev_alloc();
	257	if (!cdev)
	258	goto out2;
	259
	260	cdev->owner = fops->owner;
	261	cdev->ops = fops;
	262	kobject_set_name(&cdev->kobj, "%s", name);
	263	for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
	264	*s = '!';
	265
	266	err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
	267	if (err)
	268	goto out;
	269
	270	cd->cdev = cdev;
	271
	272	return major ? 0 : cd->major;
	273	out:
	274	kobject_put(&cdev->kobj);
	275	out2:
	276	kfree(__unregister_chrdev_region(cd->major, 0, 256));
	277	return err;
	278	}
	279
	280	void unregister_chrdev_region(dev_t from, unsigned count)
	281	{
	282	dev_t to = from + count;
	283	dev_t n, next;
	284
	285	for (n = from; n < to; n = next) {
	286	next = MKDEV(MAJOR(n)+1, 0);
	287	if (next > to)
	288	next = to;
	289	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	290	}
	291	}
	292
	293	int unregister_chrdev(unsigned int major, const char *name)
	294	{
	295	struct char_device_struct *cd;
	296	cd = __unregister_chrdev_region(major, 0, 256);
	297	if (cd && cd->cdev)
	298	cdev_del(cd->cdev);
	299	kfree(cd);
	300	return 0;
	301	}
	302
	303	static DEFINE_SPINLOCK(cdev_lock);
	304
	305	static struct kobject cdev_get(struct cdev p)
	306	{
	307	struct module *owner = p->owner;
	308	struct kobject *kobj;
	309
310	if (owner && !try_module_get(owner))
311	return NULL;
312	kobj = kobject_get(&p->kobj);
313	if (!kobj)
314	module_put(owner);
315	return kobj;
316	}
317
318	void cdev_put(struct cdev *p)
319	{
320	if (p) {
7da6844c	321	struct module *owner = p->owner;
1da177e4	322	kobject_put(&p->kobj);
7da6844c	323	module_put(owner);
1da177e4 LT	324	}
	325	}
	326
	327	/*
	328	* Called every time a character special file is opened
	329	*/
	330	int chrdev_open(struct inode * inode, struct file * filp)
	331	{
	332	struct cdev *p;
	333	struct cdev *new = NULL;
	334	int ret = 0;
	335
	336	spin_lock(&cdev_lock);
	337	p = inode->i_cdev;
	338	if (!p) {
	339	struct kobject *kobj;
	340	int idx;
	341	spin_unlock(&cdev_lock);
	342	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	343	if (!kobj)
	344	return -ENXIO;
	345	new = container_of(kobj, struct cdev, kobj);
	346	spin_lock(&cdev_lock);
	347	p = inode->i_cdev;
	348	if (!p) {
	349	inode->i_cdev = p = new;
	350	inode->i_cindex = idx;
	351	list_add(&inode->i_devices, &p->list);
	352	new = NULL;
	353	} else if (!cdev_get(p))
	354	ret = -ENXIO;
	355	} else if (!cdev_get(p))
	356	ret = -ENXIO;
	357	spin_unlock(&cdev_lock);
	358	cdev_put(new);
	359	if (ret)
	360	return ret;
	361	filp->f_op = fops_get(p->ops);
	362	if (!filp->f_op) {
	363	cdev_put(p);
	364	return -ENXIO;
	365	}
	366	if (filp->f_op->open) {
	367	lock_kernel();
	368	ret = filp->f_op->open(inode,filp);
	369	unlock_kernel();
	370	}
	371	if (ret)
	372	cdev_put(p);
	373	return ret;
	374	}
	375
	376	void cd_forget(struct inode *inode)
	377	{
	378	spin_lock(&cdev_lock);
	379	list_del_init(&inode->i_devices);
	380	inode->i_cdev = NULL;
	381	spin_unlock(&cdev_lock);
	382	}
	383
75c96f85	384	static void cdev_purge(struct cdev *cdev)
1da177e4 LT	385	{
	386	spin_lock(&cdev_lock);
	387	while (!list_empty(&cdev->list)) {
	388	struct inode *inode;
	389	inode = container_of(cdev->list.next, struct inode, i_devices);
	390	list_del_init(&inode->i_devices);
	391	inode->i_cdev = NULL;
	392	}
	393	spin_unlock(&cdev_lock);
	394	}
	395
	396	/*
	397	* Dummy default file-operations: the only thing this does
	398	* is contain the open that then fills in the correct operations
	399	* depending on the special file...
	400	*/
4b6f5d20	401	const struct file_operations def_chr_fops = {
1da177e4 LT	402	.open = chrdev_open,
	403	};
	404
	405	static struct kobject exact_match(dev_t dev, int part, void *data)
	406	{
	407	struct cdev *p = data;
	408	return &p->kobj;
	409	}
	410
	411	static int exact_lock(dev_t dev, void *data)
	412	{
	413	struct cdev *p = data;
	414	return cdev_get(p) ? 0 : -1;
	415	}
	416
	417	int cdev_add(struct cdev *p, dev_t dev, unsigned count)
	418	{
	419	p->dev = dev;
	420	p->count = count;
	421	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
	422	}
	423
	424	static void cdev_unmap(dev_t dev, unsigned count)
	425	{
	426	kobj_unmap(cdev_map, dev, count);
	427	}
	428
	429	void cdev_del(struct cdev *p)
	430	{
	431	cdev_unmap(p->dev, p->count);
	432	kobject_put(&p->kobj);
	433	}
	434
	435
	436	static void cdev_default_release(struct kobject *kobj)
	437	{
	438	struct cdev *p = container_of(kobj, struct cdev, kobj);
	439	cdev_purge(p);
	440	}
	441
	442	static void cdev_dynamic_release(struct kobject *kobj)
	443	{
	444	struct cdev *p = container_of(kobj, struct cdev, kobj);
	445	cdev_purge(p);
	446	kfree(p);
	447	}
	448
	449	static struct kobj_type ktype_cdev_default = {
	450	.release = cdev_default_release,
	451	};
	452
	453	static struct kobj_type ktype_cdev_dynamic = {
	454	.release = cdev_dynamic_release,
	455	};
	456
	457	struct cdev *cdev_alloc(void)
	458	{
11b0b5ab	459	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
1da177e4	460	if (p) {
1da177e4 LT	461	p->kobj.ktype = &ktype_cdev_dynamic;
	462	INIT_LIST_HEAD(&p->list);
	463	kobject_init(&p->kobj);
	464	}
	465	return p;
	466	}
	467
99ac48f5	468	void cdev_init(struct cdev cdev, const struct file_operations fops)
1da177e4 LT	469	{
	470	memset(cdev, 0, sizeof *cdev);
	471	INIT_LIST_HEAD(&cdev->list);
	472	cdev->kobj.ktype = &ktype_cdev_default;
	473	kobject_init(&cdev->kobj);
	474	cdev->ops = fops;
	475	}
	476
	477	static struct kobject base_probe(dev_t dev, int part, void *data)
	478	{
	479	if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
	480	/* Make old-style 2.4 aliases work */
	481	request_module("char-major-%d", MAJOR(dev));
	482	return NULL;
	483	}
	484
	485	void __init chrdev_init(void)
	486	{
	487	cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
	488	}
	489
	490
	491	/* Let modules do char dev stuff */
	492	EXPORT_SYMBOL(register_chrdev_region);
	493	EXPORT_SYMBOL(unregister_chrdev_region);
	494	EXPORT_SYMBOL(alloc_chrdev_region);
	495	EXPORT_SYMBOL(cdev_init);
	496	EXPORT_SYMBOL(cdev_alloc);
	497	EXPORT_SYMBOL(cdev_del);
	498	EXPORT_SYMBOL(cdev_add);
	499	EXPORT_SYMBOL(register_chrdev);
	500	EXPORT_SYMBOL(unregister_chrdev);
5da6185b	501	EXPORT_SYMBOL(directly_mappable_cdev_bdi);