/* * linux/drivers/char/misc.c * * Generic misc open routine by Johan Myreen * * Based on code from Linus * * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's *   changes incorporated into 0.97pl4 *   by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92) *   See busmouse.c for particulars. * * Made things a lot mode modular - easy to compile in just one or two * of the misc drivers, as they are now completely independent. Linus. * * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk> * * Fixed a failing symbol register to free the device registration *		Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96 * * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96 * * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96 * * Handling of mouse minor numbers for kerneld: *  Idea by Jacques Gelinas <jack@solucorp.qc.ca>, *  adapted by Bjorn Ekwall <bj0rn@blox.se> *  corrected by Alan Cox <alan@lxorguk.ukuu.org.uk> * * Changes for kmod (from kerneld): *	Cyrus Durgin <cider@speakeasy.org> * * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au>  10-Jan-1998 */ #include <linux/module.h> #include <linux/fs.h>#include <linux/errno.h>#include <linux/miscdevice.h>#include <linux/kernel.h>#include <linux/major.h>#include <linux/slab.h>#include <linux/proc_fs.h>#include <linux/seq_file.h>#include <linux/stat.h>#include <linux/init.h>#include <linux/device.h>#include <linux/tty.h>#include <linux/kmod.h> /* * Head entry for the doubly linked miscdevice list */static LIST_HEAD(misc_list);static DECLARE_MUTEX(misc_sem); /* * Assigned numbers, used for dynamic minors */#define DYNAMIC_MINORS 64 /* like dynamic majors */static unsigned char misc_minors[DYNAMIC_MINORS / 8]; extern int pmu_device_init(void); #ifdef CONFIG_PROC_FSstatic void *misc_seq_start(struct seq_file *seq, loff_t *pos){	struct miscdevice *p;	loff_t off = 0; 	down(&misc_sem);	list_for_each_entry(p, &misc_list, list) {		if (*pos == off++) 			return p;	}	return NULL;} static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos){	struct list_head *n = ((struct miscdevice *)v)->list.next; 	++*pos; 	return (n != &misc_list) ? list_entry(n, struct miscdevice, list)		 : NULL;} static void misc_seq_stop(struct seq_file *seq, void *v){	up(&misc_sem);} static int misc_seq_show(struct seq_file *seq, void *v){	const struct miscdevice *p = v; 	seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");	return 0;}  static struct seq_operations misc_seq_ops = {	.start = misc_seq_start,	.next  = misc_seq_next,	.stop  = misc_seq_stop,	.show  = misc_seq_show,}; static int misc_seq_open(struct inode *inode, struct file *file){	return seq_open(file, &misc_seq_ops);} static const struct file_operations misc_proc_fops = {	.owner	 = THIS_MODULE,	.open    = misc_seq_open,	.read    = seq_read,	.llseek  = seq_lseek,	.release = seq_release,};#endif static int misc_open(struct inode * inode, struct file * file){	int minor = iminor(inode);	struct miscdevice *c;	int err = -ENODEV;	const struct file_operations *old_fops, *new_fops = NULL;		down(&misc_sem);		list_for_each_entry(c, &misc_list, list) {		if (c->minor == minor) {			new_fops = fops_get(c->fops);					break;		}	}			if (!new_fops) {		up(&misc_sem);		request_module("char-major-%d-%d", MISC_MAJOR, minor);		down(&misc_sem); 		list_for_each_entry(c, &misc_list, list) {			if (c->minor == minor) {				new_fops = fops_get(c->fops);				break;			}		}		if (!new_fops)			goto fail;	} 	err = 0;	old_fops = file->f_op;	file->f_op = new_fops;	if (file->f_op->open) {		err=file->f_op->open(inode,file);		if (err) {			fops_put(file->f_op);			file->f_op = fops_get(old_fops);		}	}	fops_put(old_fops);fail:	up(&misc_sem);	return err;} static struct class *misc_class; static const struct file_operations misc_fops = {	.owner		= THIS_MODULE,	.open		= misc_open,};  /** *	misc_register	-	register a miscellaneous device *	@misc: device structure *	 *	Register a miscellaneous device with the kernel. If the minor *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned *	and placed in the minor field of the structure. For other cases *	the minor number requested is used. * *	The structure passed is linked into the kernel and may not be *	destroyed until it has been unregistered. * *	A zero is returned on success and a negative errno code for *	failure. */ int misc_register(struct miscdevice * misc){	struct miscdevice *c;	dev_t dev;	int err = 0; 	INIT_LIST_HEAD(&misc->list); 	down(&misc_sem);	list_for_each_entry(c, &misc_list, list) {		if (c->minor == misc->minor) {			up(&misc_sem);			return -EBUSY;		}	} 	if (misc->minor == MISC_DYNAMIC_MINOR) {		int i = DYNAMIC_MINORS;		while (--i >= 0)			if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)				break;		if (i<0) {			up(&misc_sem);			return -EBUSY;		}		misc->minor = i;	} 	if (misc->minor < DYNAMIC_MINORS)		misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);	dev = MKDEV(MISC_MAJOR, misc->minor); 	misc->this_device = device_create(misc_class, misc->parent, dev,					  "%s", misc->name);	if (IS_ERR(misc->this_device)) {		err = PTR_ERR(misc->this_device);		goto out;	} 	/*	 * Add it to the front, so that later devices can "override"	 * earlier defaults	 */	list_add(&misc->list, &misc_list); out:	up(&misc_sem);	return err;} /** *	misc_deregister - unregister a miscellaneous device *	@misc: device to unregister * *	Unregister a miscellaneous device that was previously *	successfully registered with misc_register(). Success *	is indicated by a zero return, a negative errno code *	indicates an error. */ int misc_deregister(struct miscdevice * misc){	int i = misc->minor; 	if (list_empty(&misc->list))		return -EINVAL; 	down(&misc_sem);	list_del(&misc->list);	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));	if (i < DYNAMIC_MINORS && i>0) {		misc_minors[i>>3] &= ~(1 << (misc->minor & 7));	}	up(&misc_sem);	return 0;} EXPORT_SYMBOL(misc_register);EXPORT_SYMBOL(misc_deregister); static int __init misc_init(void){#ifdef CONFIG_PROC_FS	struct proc_dir_entry *ent; 	ent = create_proc_entry("misc", 0, NULL);	if (ent)		ent->proc_fops = &misc_proc_fops;#endif	misc_class = class_create(THIS_MODULE, "misc");	if (IS_ERR(misc_class))		return PTR_ERR(misc_class); 	if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {		printk("unable to get major %d for misc devices\n",		       MISC_MAJOR);		class_destroy(misc_class);		return -EIO;	}	return 0;}subsys_initcall(misc_init);