[linux.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/kdev_t.h>
#include <linux/slab.h>
#include <linux/string.h>

#include <linux/major.h>
#include <linux/errno.h>
#include <linux/module.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>
#include <linux/tty.h>

#include "internal.h"

/*
 * 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 = {
	.name = "char",
	.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 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;
	strlcpy(cd->name, name, sizeof(cd->name));

	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;
}

/**
 * register_chrdev_region() - register a range of device numbers
 * @from: the first in the desired range of device numbers; must include
 *        the major number.
 * @count: the number of consecutive device numbers required
 * @name: the name of the device or driver.
 *
 * Return value is zero on success, a negative error code on failure.
 */
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);
}

/**
 * alloc_chrdev_region() - register a range of char device numbers
 * @dev: output parameter for first assigned number
 * @baseminor: first of the requested range of minor numbers
 * @count: the number of minor numbers required
 * @name: the name of the associated device or driver
 *
 * Allocates a range of char device numbers.  The major number will be
 * chosen dynamically, and returned (along with the first minor number)
 * in @dev.  Returns zero or a negative error code.
 */
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() - create and register a cdev occupying a range of minors
 * @major: major device number or 0 for dynamic allocation
 * @baseminor: first of the requested range of minor numbers
 * @count: the number of minor numbers required
 * @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.
 */
int __register_chrdev(unsigned int major, unsigned int baseminor,
		      unsigned int count, const char *name,
		      const struct file_operations *fops)
{
	struct char_device_struct *cd;
	struct cdev *cdev;
	int err = -ENOMEM;

	cd = __register_chrdev_region(major, baseminor, count, 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);
		
	err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
	if (err)
		goto out;

	cd->cdev = cdev;

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

/**
 * unregister_chrdev_region() - return a range of device numbers
 * @from: the first in the range of numbers to unregister
 * @count: the number of device numbers to unregister
 *
 * This function will unregister a range of @count device numbers,
 * starting with @from.  The caller should normally be the one who
 * allocated those numbers in the first place...
 */
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));
	}
}

/**
 * __unregister_chrdev - unregister and destroy a cdev
 * @major: major device number
 * @baseminor: first of the range of minor numbers
 * @count: the number of minor numbers this cdev is occupying
 * @name: name of this range of devices
 *
 * Unregister and destroy the cdev occupying the region described by
 * @major, @baseminor and @count.  This function undoes what
 * __register_chrdev() did.
 */
void __unregister_chrdev(unsigned int major, unsigned int baseminor,
			 unsigned int count, const char *name)
{
	struct char_device_struct *cd;

	cd = __unregister_chrdev_region(major, baseminor, count);
	if (cd && cd->cdev)
		cdev_del(cd->cdev);
	kfree(cd);
}

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
 */
static 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);
		/* Check i_cdev again in case somebody beat us to it while
		   we dropped the lock. */
		p = inode->i_cdev;
		if (!p) {
			inode->i_cdev = p = new;
			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;

	ret = -ENXIO;
	filp->f_op = fops_get(p->ops);
	if (!filp->f_op)
		goto out_cdev_put;

	if (filp->f_op->open) {
		ret = filp->f_op->open(inode,filp);
		if (ret)
			goto out_cdev_put;
	}

	return 0;

 out_cdev_put:
	cdev_put(p);
	return ret;
}

int cdev_index(struct inode *inode)
{
	int idx;
	struct kobject *kobj;

	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	if (!kobj)
		return -1;
	kobject_put(kobj);
	return idx;
}

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;
}

/**
 * cdev_add() - add a char device to the system
 * @p: the cdev structure for the device
 * @dev: the first device number for which this device is responsible
 * @count: the number of consecutive minor numbers corresponding to this
 *         device
 *
 * cdev_add() adds the device represented by @p to the system, making it
 * live immediately.  A negative error code is returned on failure.
 */
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);
}

/**
 * cdev_del() - remove a cdev from the system
 * @p: the cdev structure to be removed
 *
 * cdev_del() removes @p from the system, possibly freeing the structure
 * itself.
 */
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,
};

/**
 * cdev_alloc() - allocate a cdev structure
 *
 * Allocates and returns a cdev structure, or NULL on failure.
 */
struct cdev *cdev_alloc(void)
{
	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
	if (p) {
		INIT_LIST_HEAD(&p->list);
		kobject_init(&p->kobj, &ktype_cdev_dynamic);
	}
	return p;
}

/**
 * cdev_init() - initialize a cdev structure
 * @cdev: the structure to initialize
 * @fops: the file_operations for this device
 *
 * Initializes @cdev, remembering @fops, making it ready to add to the
 * system with cdev_add().
 */
void cdev_init(struct cdev *cdev, const struct file_operations *fops)
{
	memset(cdev, 0, sizeof *cdev);
	INIT_LIST_HEAD(&cdev->list);
	kobject_init(&cdev->kobj, &ktype_cdev_default);
	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);
	bdi_init(&directly_mappable_cdev_bdi);
}


/* 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(cdev_index);
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>
1da177e4 LT	8	#include <linux/fs.h>
b446b60e	9	#include <linux/kdev_t.h>
1da177e4 LT	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>
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>
31d1d48e	23	#include <linux/tty.h>
1da177e4	24
07f3f05c	25	#include "internal.h"
1da177e4	26
5da6185b DH	27	/*
	28	* capabilities for /dev/mem, /dev/kmem and similar directly mappable character
	29	* devices
	30	* - permits shared-mmap for read, write and/or exec
	31	* - does not permit private mmap in NOMMU mode (can't do COW)
	32	* - no readahead or I/O queue unplugging required
	33	*/
	34	struct backing_dev_info directly_mappable_cdev_bdi = {
d993831f	35	.name = "char",
5da6185b DH	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	56	struct cdev cdev; / will die */
68eef3b4	57	} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
1da177e4 LT	58
	59	/* index in the above */
	60	static inline int major_to_index(int major)
	61	{
68eef3b4	62	return major % CHRDEV_MAJOR_HASH_SIZE;
7170be5f NH	63	}
7170be5f NH	64
68eef3b4	65	#ifdef CONFIG_PROC_FS
7170be5f	66
68eef3b4	67	void chrdev_show(struct seq_file *f, off_t offset)
7170be5f NH	68	{
7170be5f NH	69	struct char_device_struct *cd;
7170be5f	70
68eef3b4 JK	71	if (offset < CHRDEV_MAJOR_HASH_SIZE) {
	72	mutex_lock(&chrdevs_lock);
	73	for (cd = chrdevs[offset]; cd; cd = cd->next)
	74	seq_printf(f, "%3d %s\n", cd->major, cd->name);
	75	mutex_unlock(&chrdevs_lock);
1da177e4	76	}
7170be5f NH	77	}
7170be5f NH	78
68eef3b4	79	#endif /* CONFIG_PROC_FS */
1da177e4 LT	80
	81	/*
	82	* Register a single major with a specified minor range.
	83	*
	84	* If major == 0 this functions will dynamically allocate a major and return
	85	* its number.
	86	*
	87	* If major > 0 this function will attempt to reserve the passed range of
	88	* minors and will return zero on success.
	89	*
	90	* Returns a -ve errno on failure.
	91	*/
	92	static struct char_device_struct *
	93	__register_chrdev_region(unsigned int major, unsigned int baseminor,
	94	int minorct, const char *name)
	95	{
	96	struct char_device_struct cd, *cp;
	97	int ret = 0;
	98	int i;
	99
11b0b5ab	100	cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
1da177e4 LT	101	if (cd == NULL)
	102	return ERR_PTR(-ENOMEM);
	103
58383af6	104	mutex_lock(&chrdevs_lock);
1da177e4 LT	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;
8c401888	124	strlcpy(cd->name, name, sizeof(cd->name));
1da177e4 LT	125
	126	i = major_to_index(major);
	127
	128	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	129	if ((*cp)->major > major \|\|
01d553d0 AW	130	((*cp)->major == major &&
	131	(((*cp)->baseminor >= baseminor) \|\|
	132	((cp)->baseminor + (cp)->minorct > baseminor))))
1da177e4	133	break;
01d553d0 AW	134
	135	/* Check for overlapping minor ranges. */
	136	if (cp && (cp)->major == major) {
	137	int old_min = (*cp)->baseminor;
	138	int old_max = (cp)->baseminor + (cp)->minorct - 1;
	139	int new_min = baseminor;
	140	int new_max = baseminor + minorct - 1;
	141
	142	/* New driver overlaps from the left. */
	143	if (new_max >= old_min && new_max <= old_max) {
	144	ret = -EBUSY;
	145	goto out;
	146	}
	147
	148	/* New driver overlaps from the right. */
	149	if (new_min <= old_max && new_min >= old_min) {
	150	ret = -EBUSY;
	151	goto out;
	152	}
1da177e4	153	}
01d553d0	154
1da177e4 LT	155	cd->next = *cp;
1da177e4 LT	156	*cp = cd;
58383af6	157	mutex_unlock(&chrdevs_lock);
1da177e4 LT	158	return cd;
1da177e4 LT	159	out:
58383af6	160	mutex_unlock(&chrdevs_lock);
1da177e4 LT	161	kfree(cd);
	162	return ERR_PTR(ret);
	163	}
	164
	165	static struct char_device_struct *
	166	__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
	167	{
	168	struct char_device_struct cd = NULL, *cp;
	169	int i = major_to_index(major);
	170
58383af6	171	mutex_lock(&chrdevs_lock);
1da177e4 LT	172	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	173	if ((*cp)->major == major &&
	174	(*cp)->baseminor == baseminor &&
	175	(*cp)->minorct == minorct)
	176	break;
	177	if (*cp) {
	178	cd = *cp;
	179	*cp = cd->next;
	180	}
58383af6	181	mutex_unlock(&chrdevs_lock);
1da177e4 LT	182	return cd;
	183	}
	184
cf3e43db JC	185	/**
	186	* register_chrdev_region() - register a range of device numbers
	187	* @from: the first in the desired range of device numbers; must include
	188	* the major number.
	189	* @count: the number of consecutive device numbers required
	190	* @name: the name of the device or driver.
	191	*
	192	* Return value is zero on success, a negative error code on failure.
	193	*/
1da177e4 LT	194	int register_chrdev_region(dev_t from, unsigned count, const char *name)
	195	{
	196	struct char_device_struct *cd;
	197	dev_t to = from + count;
	198	dev_t n, next;
	199
	200	for (n = from; n < to; n = next) {
	201	next = MKDEV(MAJOR(n)+1, 0);
	202	if (next > to)
	203	next = to;
	204	cd = __register_chrdev_region(MAJOR(n), MINOR(n),
	205	next - n, name);
	206	if (IS_ERR(cd))
	207	goto fail;
	208	}
	209	return 0;
	210	fail:
	211	to = n;
	212	for (n = from; n < to; n = next) {
	213	next = MKDEV(MAJOR(n)+1, 0);
	214	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	215	}
	216	return PTR_ERR(cd);
	217	}
	218
cf3e43db JC	219	/**
	220	* alloc_chrdev_region() - register a range of char device numbers
	221	* @dev: output parameter for first assigned number
	222	* @baseminor: first of the requested range of minor numbers
	223	* @count: the number of minor numbers required
	224	* @name: the name of the associated device or driver
	225	*
	226	* Allocates a range of char device numbers. The major number will be
	227	* chosen dynamically, and returned (along with the first minor number)
	228	* in @dev. Returns zero or a negative error code.
	229	*/
1da177e4 LT	230	int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
	231	const char *name)
	232	{
	233	struct char_device_struct *cd;
	234	cd = __register_chrdev_region(0, baseminor, count, name);
	235	if (IS_ERR(cd))
	236	return PTR_ERR(cd);
	237	*dev = MKDEV(cd->major, cd->baseminor);
	238	return 0;
	239	}
	240
d247e2c6	241	/**
1905b1bf	242	* __register_chrdev() - create and register a cdev occupying a range of minors
d247e2c6	243	* @major: major device number or 0 for dynamic allocation
1905b1bf TH	244	* @baseminor: first of the requested range of minor numbers
1905b1bf TH	245	* @count: the number of minor numbers required
d247e2c6 REB	246	* @name: name of this range of devices
	247	* @fops: file operations associated with this devices
	248	*
	249	* If @major == 0 this functions will dynamically allocate a major and return
	250	* its number.
	251	*
	252	* If @major > 0 this function will attempt to reserve a device with the given
	253	* major number and will return zero on success.
	254	*
	255	* Returns a -ve errno on failure.
	256	*
	257	* The name of this device has nothing to do with the name of the device in
	258	* /dev. It only helps to keep track of the different owners of devices. If
	259	* your module name has only one type of devices it's ok to use e.g. the name
	260	* of the module here.
d247e2c6	261	*/
1905b1bf TH	262	int __register_chrdev(unsigned int major, unsigned int baseminor,
	263	unsigned int count, const char *name,
	264	const struct file_operations *fops)
1da177e4 LT	265	{
	266	struct char_device_struct *cd;
	267	struct cdev *cdev;
1da177e4 LT	268	int err = -ENOMEM;
1da177e4 LT	269
1905b1bf	270	cd = __register_chrdev_region(major, baseminor, count, name);
1da177e4 LT	271	if (IS_ERR(cd))
	272	return PTR_ERR(cd);
	273
	274	cdev = cdev_alloc();
	275	if (!cdev)
	276	goto out2;
	277
	278	cdev->owner = fops->owner;
	279	cdev->ops = fops;
	280	kobject_set_name(&cdev->kobj, "%s", name);
1da177e4	281
1905b1bf	282	err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
1da177e4 LT	283	if (err)
	284	goto out;
	285
	286	cd->cdev = cdev;
	287
	288	return major ? 0 : cd->major;
	289	out:
	290	kobject_put(&cdev->kobj);
	291	out2:
1905b1bf	292	kfree(__unregister_chrdev_region(cd->major, baseminor, count));
1da177e4 LT	293	return err;
	294	}
	295
cf3e43db JC	296	/**
	297	* unregister_chrdev_region() - return a range of device numbers
	298	* @from: the first in the range of numbers to unregister
	299	* @count: the number of device numbers to unregister
	300	*
	301	* This function will unregister a range of @count device numbers,
	302	* starting with @from. The caller should normally be the one who
	303	* allocated those numbers in the first place...
	304	*/
1da177e4 LT	305	void unregister_chrdev_region(dev_t from, unsigned count)
	306	{
	307	dev_t to = from + count;
	308	dev_t n, next;
	309
	310	for (n = from; n < to; n = next) {
	311	next = MKDEV(MAJOR(n)+1, 0);
	312	if (next > to)
	313	next = to;
	314	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	315	}
	316	}
	317
1905b1bf TH	318	/**
	319	* __unregister_chrdev - unregister and destroy a cdev
	320	* @major: major device number
	321	* @baseminor: first of the range of minor numbers
	322	* @count: the number of minor numbers this cdev is occupying
	323	* @name: name of this range of devices
	324	*
	325	* Unregister and destroy the cdev occupying the region described by
	326	* @major, @baseminor and @count. This function undoes what
	327	* __register_chrdev() did.
	328	*/
	329	void __unregister_chrdev(unsigned int major, unsigned int baseminor,
	330	unsigned int count, const char *name)
1da177e4 LT	331	{
1da177e4 LT	332	struct char_device_struct *cd;
1905b1bf TH	333
1905b1bf TH	334	cd = __unregister_chrdev_region(major, baseminor, count);
1da177e4 LT	335	if (cd && cd->cdev)
	336	cdev_del(cd->cdev);
	337	kfree(cd);
1da177e4 LT	338	}
	339
	340	static DEFINE_SPINLOCK(cdev_lock);
	341
	342	static struct kobject cdev_get(struct cdev p)
	343	{
	344	struct module *owner = p->owner;
	345	struct kobject *kobj;
	346
	347	if (owner && !try_module_get(owner))
	348	return NULL;
	349	kobj = kobject_get(&p->kobj);
	350	if (!kobj)
	351	module_put(owner);
	352	return kobj;
	353	}
	354
	355	void cdev_put(struct cdev *p)
	356	{
	357	if (p) {
7da6844c	358	struct module *owner = p->owner;
1da177e4	359	kobject_put(&p->kobj);
7da6844c	360	module_put(owner);
1da177e4 LT	361	}
	362	}
	363
	364	/*
	365	* Called every time a character special file is opened
	366	*/
922f9cfa	367	static int chrdev_open(struct inode inode, struct file filp)
1da177e4 LT	368	{
	369	struct cdev *p;
	370	struct cdev *new = NULL;
	371	int ret = 0;
	372
	373	spin_lock(&cdev_lock);
	374	p = inode->i_cdev;
	375	if (!p) {
	376	struct kobject *kobj;
	377	int idx;
	378	spin_unlock(&cdev_lock);
	379	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	380	if (!kobj)
	381	return -ENXIO;
	382	new = container_of(kobj, struct cdev, kobj);
	383	spin_lock(&cdev_lock);
a30427d9 JC	384	/* Check i_cdev again in case somebody beat us to it while
a30427d9 JC	385	we dropped the lock. */
1da177e4 LT	386	p = inode->i_cdev;
	387	if (!p) {
	388	inode->i_cdev = p = new;
1da177e4 LT	389	list_add(&inode->i_devices, &p->list);
	390	new = NULL;
	391	} else if (!cdev_get(p))
	392	ret = -ENXIO;
	393	} else if (!cdev_get(p))
	394	ret = -ENXIO;
	395	spin_unlock(&cdev_lock);
	396	cdev_put(new);
	397	if (ret)
	398	return ret;
a518ab93 CH	399
a518ab93 CH	400	ret = -ENXIO;
1da177e4	401	filp->f_op = fops_get(p->ops);
a518ab93 CH	402	if (!filp->f_op)
	403	goto out_cdev_put;
	404
	405	if (filp->f_op->open) {
1da177e4	406	ret = filp->f_op->open(inode,filp);
a518ab93 CH	407	if (ret)
	408	goto out_cdev_put;
	409	}
	410
	411	return 0;
	412
	413	out_cdev_put:
	414	cdev_put(p);
1da177e4 LT	415	return ret;
	416	}
	417
9fd5746f TT	418	int cdev_index(struct inode *inode)
	419	{
	420	int idx;
	421	struct kobject *kobj;
	422
	423	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	424	if (!kobj)
	425	return -1;
	426	kobject_put(kobj);
	427	return idx;
	428	}
	429
1da177e4 LT	430	void cd_forget(struct inode *inode)
	431	{
	432	spin_lock(&cdev_lock);
	433	list_del_init(&inode->i_devices);
	434	inode->i_cdev = NULL;
	435	spin_unlock(&cdev_lock);
	436	}
	437
75c96f85	438	static void cdev_purge(struct cdev *cdev)
1da177e4 LT	439	{
	440	spin_lock(&cdev_lock);
	441	while (!list_empty(&cdev->list)) {
	442	struct inode *inode;
	443	inode = container_of(cdev->list.next, struct inode, i_devices);
	444	list_del_init(&inode->i_devices);
	445	inode->i_cdev = NULL;
	446	}
	447	spin_unlock(&cdev_lock);
	448	}
	449
	450	/*
	451	* Dummy default file-operations: the only thing this does
	452	* is contain the open that then fills in the correct operations
	453	* depending on the special file...
	454	*/
4b6f5d20	455	const struct file_operations def_chr_fops = {
1da177e4 LT	456	.open = chrdev_open,
	457	};
	458
	459	static struct kobject exact_match(dev_t dev, int part, void *data)
	460	{
	461	struct cdev *p = data;
	462	return &p->kobj;
	463	}
	464
	465	static int exact_lock(dev_t dev, void *data)
	466	{
	467	struct cdev *p = data;
	468	return cdev_get(p) ? 0 : -1;
	469	}
	470
cf3e43db JC	471	/**
	472	* cdev_add() - add a char device to the system
	473	* @p: the cdev structure for the device
	474	* @dev: the first device number for which this device is responsible
	475	* @count: the number of consecutive minor numbers corresponding to this
	476	* device
	477	*
	478	* cdev_add() adds the device represented by @p to the system, making it
	479	* live immediately. A negative error code is returned on failure.
	480	*/
1da177e4 LT	481	int cdev_add(struct cdev *p, dev_t dev, unsigned count)
	482	{
	483	p->dev = dev;
	484	p->count = count;
	485	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
	486	}
	487
	488	static void cdev_unmap(dev_t dev, unsigned count)
	489	{
	490	kobj_unmap(cdev_map, dev, count);
	491	}
	492
cf3e43db JC	493	/**
	494	* cdev_del() - remove a cdev from the system
	495	* @p: the cdev structure to be removed
	496	*
	497	* cdev_del() removes @p from the system, possibly freeing the structure
	498	* itself.
	499	*/
1da177e4 LT	500	void cdev_del(struct cdev *p)
	501	{
	502	cdev_unmap(p->dev, p->count);
	503	kobject_put(&p->kobj);
	504	}
	505
	506
	507	static void cdev_default_release(struct kobject *kobj)
	508	{
	509	struct cdev *p = container_of(kobj, struct cdev, kobj);
	510	cdev_purge(p);
	511	}
	512
	513	static void cdev_dynamic_release(struct kobject *kobj)
	514	{
	515	struct cdev *p = container_of(kobj, struct cdev, kobj);
	516	cdev_purge(p);
	517	kfree(p);
	518	}
	519
	520	static struct kobj_type ktype_cdev_default = {
	521	.release = cdev_default_release,
	522	};
	523
	524	static struct kobj_type ktype_cdev_dynamic = {
	525	.release = cdev_dynamic_release,
	526	};
	527
cf3e43db JC	528	/**
	529	* cdev_alloc() - allocate a cdev structure
	530	*
	531	* Allocates and returns a cdev structure, or NULL on failure.
	532	*/
1da177e4 LT	533	struct cdev *cdev_alloc(void)
1da177e4 LT	534	{
11b0b5ab	535	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
1da177e4	536	if (p) {
1da177e4	537	INIT_LIST_HEAD(&p->list);
f9cb074b	538	kobject_init(&p->kobj, &ktype_cdev_dynamic);
1da177e4 LT	539	}
	540	return p;
	541	}
	542
cf3e43db JC	543	/**
	544	* cdev_init() - initialize a cdev structure
	545	* @cdev: the structure to initialize
	546	* @fops: the file_operations for this device
	547	*
	548	* Initializes @cdev, remembering @fops, making it ready to add to the
	549	* system with cdev_add().
	550	*/
99ac48f5	551	void cdev_init(struct cdev cdev, const struct file_operations fops)
1da177e4 LT	552	{
	553	memset(cdev, 0, sizeof *cdev);
	554	INIT_LIST_HEAD(&cdev->list);
f9cb074b	555	kobject_init(&cdev->kobj, &ktype_cdev_default);
1da177e4 LT	556	cdev->ops = fops;
	557	}
	558
	559	static struct kobject base_probe(dev_t dev, int part, void *data)
	560	{
	561	if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
	562	/* Make old-style 2.4 aliases work */
	563	request_module("char-major-%d", MAJOR(dev));
	564	return NULL;
	565	}
	566
	567	void __init chrdev_init(void)
	568	{
	569	cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
e0bf68dd	570	bdi_init(&directly_mappable_cdev_bdi);
1da177e4 LT	571	}
	572
	573
	574	/* Let modules do char dev stuff */
	575	EXPORT_SYMBOL(register_chrdev_region);
	576	EXPORT_SYMBOL(unregister_chrdev_region);
	577	EXPORT_SYMBOL(alloc_chrdev_region);
	578	EXPORT_SYMBOL(cdev_init);
	579	EXPORT_SYMBOL(cdev_alloc);
	580	EXPORT_SYMBOL(cdev_del);
	581	EXPORT_SYMBOL(cdev_add);
9fd5746f	582	EXPORT_SYMBOL(cdev_index);
1905b1bf TH	583	EXPORT_SYMBOL(__register_chrdev);
1905b1bf TH	584	EXPORT_SYMBOL(__unregister_chrdev);
5da6185b	585	EXPORT_SYMBOL(directly_mappable_cdev_bdi);