/* *  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/seq_file.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; 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;} 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);