[net-next-2.6.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))
			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;
}

/**
 * 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 \|\|
	131	((cp)->major == major && (cp)->baseminor >= baseminor))
	132	break;
	133	if (cp && (cp)->major == major &&
	134	(*cp)->baseminor < baseminor + minorct) {
	135	ret = -EBUSY;
	136	goto out;
	137	}
	138	cd->next = *cp;
	139	*cp = cd;
58383af6	140	mutex_unlock(&chrdevs_lock);
1da177e4 LT	141	return cd;
1da177e4 LT	142	out:
58383af6	143	mutex_unlock(&chrdevs_lock);
1da177e4 LT	144	kfree(cd);
	145	return ERR_PTR(ret);
	146	}
	147
	148	static struct char_device_struct *
	149	__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
	150	{
	151	struct char_device_struct cd = NULL, *cp;
	152	int i = major_to_index(major);
	153
58383af6	154	mutex_lock(&chrdevs_lock);
1da177e4 LT	155	for (cp = &chrdevs[i]; cp; cp = &(cp)->next)
	156	if ((*cp)->major == major &&
	157	(*cp)->baseminor == baseminor &&
	158	(*cp)->minorct == minorct)
	159	break;
	160	if (*cp) {
	161	cd = *cp;
	162	*cp = cd->next;
	163	}
58383af6	164	mutex_unlock(&chrdevs_lock);
1da177e4 LT	165	return cd;
	166	}
	167
	168	int register_chrdev_region(dev_t from, unsigned count, const char *name)
	169	{
	170	struct char_device_struct *cd;
	171	dev_t to = from + count;
	172	dev_t n, next;
	173
	174	for (n = from; n < to; n = next) {
	175	next = MKDEV(MAJOR(n)+1, 0);
	176	if (next > to)
	177	next = to;
	178	cd = __register_chrdev_region(MAJOR(n), MINOR(n),
	179	next - n, name);
	180	if (IS_ERR(cd))
	181	goto fail;
	182	}
	183	return 0;
	184	fail:
	185	to = n;
	186	for (n = from; n < to; n = next) {
	187	next = MKDEV(MAJOR(n)+1, 0);
	188	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	189	}
	190	return PTR_ERR(cd);
	191	}
	192
	193	int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
	194	const char *name)
	195	{
	196	struct char_device_struct *cd;
	197	cd = __register_chrdev_region(0, baseminor, count, name);
	198	if (IS_ERR(cd))
	199	return PTR_ERR(cd);
	200	*dev = MKDEV(cd->major, cd->baseminor);
	201	return 0;
	202	}
	203
d247e2c6 REB	204	/**
	205	* register_chrdev() - Register a major number for character devices.
	206	* @major: major device number or 0 for dynamic allocation
	207	* @name: name of this range of devices
	208	* @fops: file operations associated with this devices
	209	*
	210	* If @major == 0 this functions will dynamically allocate a major and return
	211	* its number.
	212	*
	213	* If @major > 0 this function will attempt to reserve a device with the given
	214	* major number and will return zero on success.
	215	*
	216	* Returns a -ve errno on failure.
	217	*
	218	* The name of this device has nothing to do with the name of the device in
	219	* /dev. It only helps to keep track of the different owners of devices. If
	220	* your module name has only one type of devices it's ok to use e.g. the name
	221	* of the module here.
	222	*
	223	* This function registers a range of 256 minor numbers. The first minor number
	224	* is 0.
	225	*/
1da177e4	226	int register_chrdev(unsigned int major, const char *name,
99ac48f5	227	const struct file_operations *fops)
1da177e4 LT	228	{
	229	struct char_device_struct *cd;
	230	struct cdev *cdev;
	231	char *s;
	232	int err = -ENOMEM;
	233
	234	cd = __register_chrdev_region(major, 0, 256, name);
	235	if (IS_ERR(cd))
	236	return PTR_ERR(cd);
	237
	238	cdev = cdev_alloc();
	239	if (!cdev)
	240	goto out2;
	241
	242	cdev->owner = fops->owner;
	243	cdev->ops = fops;
	244	kobject_set_name(&cdev->kobj, "%s", name);
	245	for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
	246	*s = '!';
	247
	248	err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
	249	if (err)
	250	goto out;
	251
	252	cd->cdev = cdev;
	253
	254	return major ? 0 : cd->major;
	255	out:
	256	kobject_put(&cdev->kobj);
	257	out2:
	258	kfree(__unregister_chrdev_region(cd->major, 0, 256));
	259	return err;
	260	}
	261
	262	void unregister_chrdev_region(dev_t from, unsigned count)
	263	{
	264	dev_t to = from + count;
	265	dev_t n, next;
	266
	267	for (n = from; n < to; n = next) {
	268	next = MKDEV(MAJOR(n)+1, 0);
	269	if (next > to)
	270	next = to;
	271	kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
	272	}
	273	}
	274
	275	int unregister_chrdev(unsigned int major, const char *name)
	276	{
	277	struct char_device_struct *cd;
	278	cd = __unregister_chrdev_region(major, 0, 256);
	279	if (cd && cd->cdev)
	280	cdev_del(cd->cdev);
	281	kfree(cd);
	282	return 0;
	283	}
	284
	285	static DEFINE_SPINLOCK(cdev_lock);
	286
	287	static struct kobject cdev_get(struct cdev p)
	288	{
	289	struct module *owner = p->owner;
	290	struct kobject *kobj;
	291
292	if (owner && !try_module_get(owner))
293	return NULL;
294	kobj = kobject_get(&p->kobj);
295	if (!kobj)
296	module_put(owner);
297	return kobj;
298	}
299
300	void cdev_put(struct cdev *p)
301	{
302	if (p) {
7da6844c	303	struct module *owner = p->owner;
1da177e4	304	kobject_put(&p->kobj);
7da6844c	305	module_put(owner);
1da177e4 LT	306	}
	307	}
	308
	309	/*
	310	* Called every time a character special file is opened
	311	*/
	312	int chrdev_open(struct inode * inode, struct file * filp)
	313	{
	314	struct cdev *p;
	315	struct cdev *new = NULL;
	316	int ret = 0;
	317
	318	spin_lock(&cdev_lock);
	319	p = inode->i_cdev;
	320	if (!p) {
	321	struct kobject *kobj;
	322	int idx;
	323	spin_unlock(&cdev_lock);
	324	kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
	325	if (!kobj)
	326	return -ENXIO;
	327	new = container_of(kobj, struct cdev, kobj);
	328	spin_lock(&cdev_lock);
	329	p = inode->i_cdev;
	330	if (!p) {
	331	inode->i_cdev = p = new;
	332	inode->i_cindex = idx;
	333	list_add(&inode->i_devices, &p->list);
	334	new = NULL;
	335	} else if (!cdev_get(p))
	336	ret = -ENXIO;
	337	} else if (!cdev_get(p))
	338	ret = -ENXIO;
	339	spin_unlock(&cdev_lock);
	340	cdev_put(new);
	341	if (ret)
	342	return ret;
	343	filp->f_op = fops_get(p->ops);
	344	if (!filp->f_op) {
	345	cdev_put(p);
	346	return -ENXIO;
	347	}
	348	if (filp->f_op->open) {
	349	lock_kernel();
	350	ret = filp->f_op->open(inode,filp);
	351	unlock_kernel();
	352	}
	353	if (ret)
	354	cdev_put(p);
	355	return ret;
	356	}
	357
	358	void cd_forget(struct inode *inode)
	359	{
	360	spin_lock(&cdev_lock);
	361	list_del_init(&inode->i_devices);
	362	inode->i_cdev = NULL;
	363	spin_unlock(&cdev_lock);
	364	}
	365
75c96f85	366	static void cdev_purge(struct cdev *cdev)
1da177e4 LT	367	{
	368	spin_lock(&cdev_lock);
	369	while (!list_empty(&cdev->list)) {
	370	struct inode *inode;
	371	inode = container_of(cdev->list.next, struct inode, i_devices);
	372	list_del_init(&inode->i_devices);
	373	inode->i_cdev = NULL;
	374	}
	375	spin_unlock(&cdev_lock);
	376	}
	377
	378	/*
	379	* Dummy default file-operations: the only thing this does
	380	* is contain the open that then fills in the correct operations
	381	* depending on the special file...
	382	*/
4b6f5d20	383	const struct file_operations def_chr_fops = {
1da177e4 LT	384	.open = chrdev_open,
	385	};
	386
	387	static struct kobject exact_match(dev_t dev, int part, void *data)
	388	{
	389	struct cdev *p = data;
	390	return &p->kobj;
	391	}
	392
	393	static int exact_lock(dev_t dev, void *data)
	394	{
	395	struct cdev *p = data;
	396	return cdev_get(p) ? 0 : -1;
	397	}
	398
	399	int cdev_add(struct cdev *p, dev_t dev, unsigned count)
	400	{
	401	p->dev = dev;
	402	p->count = count;
	403	return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
	404	}
	405
	406	static void cdev_unmap(dev_t dev, unsigned count)
	407	{
	408	kobj_unmap(cdev_map, dev, count);
	409	}
	410
	411	void cdev_del(struct cdev *p)
	412	{
	413	cdev_unmap(p->dev, p->count);
	414	kobject_put(&p->kobj);
	415	}
	416
	417
	418	static void cdev_default_release(struct kobject *kobj)
	419	{
	420	struct cdev *p = container_of(kobj, struct cdev, kobj);
	421	cdev_purge(p);
	422	}
	423
	424	static void cdev_dynamic_release(struct kobject *kobj)
	425	{
	426	struct cdev *p = container_of(kobj, struct cdev, kobj);
	427	cdev_purge(p);
	428	kfree(p);
	429	}
	430
	431	static struct kobj_type ktype_cdev_default = {
	432	.release = cdev_default_release,
	433	};
	434
	435	static struct kobj_type ktype_cdev_dynamic = {
	436	.release = cdev_dynamic_release,
	437	};
	438
	439	struct cdev *cdev_alloc(void)
	440	{
11b0b5ab	441	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
1da177e4	442	if (p) {
1da177e4 LT	443	p->kobj.ktype = &ktype_cdev_dynamic;
	444	INIT_LIST_HEAD(&p->list);
	445	kobject_init(&p->kobj);
	446	}
	447	return p;
	448	}
	449
99ac48f5	450	void cdev_init(struct cdev cdev, const struct file_operations fops)
1da177e4 LT	451	{
	452	memset(cdev, 0, sizeof *cdev);
	453	INIT_LIST_HEAD(&cdev->list);
	454	cdev->kobj.ktype = &ktype_cdev_default;
	455	kobject_init(&cdev->kobj);
	456	cdev->ops = fops;
	457	}
	458
	459	static struct kobject base_probe(dev_t dev, int part, void *data)
	460	{
	461	if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
	462	/* Make old-style 2.4 aliases work */
	463	request_module("char-major-%d", MAJOR(dev));
	464	return NULL;
	465	}
	466
	467	void __init chrdev_init(void)
	468	{
	469	cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
	470	}
	471
	472
	473	/* Let modules do char dev stuff */
	474	EXPORT_SYMBOL(register_chrdev_region);
	475	EXPORT_SYMBOL(unregister_chrdev_region);
	476	EXPORT_SYMBOL(alloc_chrdev_region);
	477	EXPORT_SYMBOL(cdev_init);
	478	EXPORT_SYMBOL(cdev_alloc);
	479	EXPORT_SYMBOL(cdev_del);
	480	EXPORT_SYMBOL(cdev_add);
	481	EXPORT_SYMBOL(register_chrdev);
	482	EXPORT_SYMBOL(unregister_chrdev);
5da6185b	483	EXPORT_SYMBOL(directly_mappable_cdev_bdi);