// SPDX-License-Identifier: GPL-2.0 /* * 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 * * Fixed a failing symbol register to free the device registration * Alan Cox 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 , * adapted by Bjorn Ekwall * corrected by Alan Cox * * Changes for kmod (from kerneld): * Cyrus Durgin * * Added devfs support. Richard Gooch 10-Jan-1998 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Head entry for the doubly linked miscdevice list */ static LIST_HEAD(misc_list); static DEFINE_MUTEX(misc_mtx); /* * Assigned numbers, used for dynamic minors */ #define DYNAMIC_MINORS 128 /* like dynamic majors */ static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS); #ifdef CONFIG_PROC_FS static void *misc_seq_start(struct seq_file *seq, loff_t *pos) { mutex_lock(&misc_mtx); return seq_list_start(&misc_list, *pos); } static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos) { return seq_list_next(v, &misc_list, pos); } static void misc_seq_stop(struct seq_file *seq, void *v) { mutex_unlock(&misc_mtx); } static int misc_seq_show(struct seq_file *seq, void *v) { const struct miscdevice *p = list_entry(v, struct miscdevice, list); seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : ""); return 0; } static const struct seq_operations misc_seq_ops = { .start = misc_seq_start, .next = misc_seq_next, .stop = misc_seq_stop, .show = misc_seq_show, }; #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 *new_fops = NULL; mutex_lock(&misc_mtx); list_for_each_entry(c, &misc_list, list) { if (c->minor == minor) { new_fops = fops_get(c->fops); break; } } if (!new_fops) { mutex_unlock(&misc_mtx); request_module("char-major-%d-%d", MISC_MAJOR, minor); mutex_lock(&misc_mtx); list_for_each_entry(c, &misc_list, list) { if (c->minor == minor) { new_fops = fops_get(c->fops); break; } } if (!new_fops) goto fail; } /* * Place the miscdevice in the file's * private_data so it can be used by the * file operations, including f_op->open below */ file->private_data = c; err = 0; replace_fops(file, new_fops); if (file->f_op->open) err = file->f_op->open(inode, file); fail: mutex_unlock(&misc_mtx); return err; } static struct class *misc_class; static const struct file_operations misc_fops = { .owner = THIS_MODULE, .open = misc_open, .llseek = noop_llseek, }; /** * 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. By default, an open() * syscall to the device sets file->private_data to point to the * structure. Drivers don't need open in fops for this. * * A zero is returned on success and a negative errno code for * failure. */ int misc_register(struct miscdevice *misc) { dev_t dev; int err = 0; bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR); INIT_LIST_HEAD(&misc->list); mutex_lock(&misc_mtx); if (is_dynamic) { int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS); if (i >= DYNAMIC_MINORS) { err = -EBUSY; goto out; } misc->minor = DYNAMIC_MINORS - i - 1; set_bit(i, misc_minors); } else { struct miscdevice *c; list_for_each_entry(c, &misc_list, list) { if (c->minor == misc->minor) { err = -EBUSY; goto out; } } } dev = MKDEV(MISC_MAJOR, misc->minor); misc->this_device = device_create_with_groups(misc_class, misc->parent, dev, misc, misc->groups, "%s", misc->name); if (IS_ERR(misc->this_device)) { if (is_dynamic) { int i = DYNAMIC_MINORS - misc->minor - 1; if (i < DYNAMIC_MINORS && i >= 0) clear_bit(i, misc_minors); misc->minor = MISC_DYNAMIC_MINOR; } 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: mutex_unlock(&misc_mtx); return err; } /** * misc_deregister - unregister a miscellaneous device * @misc: device to unregister * * Unregister a miscellaneous device that was previously * successfully registered with misc_register(). */ void misc_deregister(struct miscdevice *misc) { int i = DYNAMIC_MINORS - misc->minor - 1; if (WARN_ON(list_empty(&misc->list))) return; mutex_lock(&misc_mtx); list_del(&misc->list); device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor)); if (i < DYNAMIC_MINORS && i >= 0) clear_bit(i, misc_minors); mutex_unlock(&misc_mtx); } EXPORT_SYMBOL(misc_register); EXPORT_SYMBOL(misc_deregister); static char *misc_devnode(struct device *dev, umode_t *mode) { struct miscdevice *c = dev_get_drvdata(dev); if (mode && c->mode) *mode = c->mode; if (c->nodename) return kstrdup(c->nodename, GFP_KERNEL); return NULL; } static int __init misc_init(void) { int err; struct proc_dir_entry *ret; ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops); misc_class = class_create(THIS_MODULE, "misc"); err = PTR_ERR(misc_class); if (IS_ERR(misc_class)) goto fail_remove; err = -EIO; if (register_chrdev(MISC_MAJOR, "misc", &misc_fops)) goto fail_printk; misc_class->devnode = misc_devnode; return 0; fail_printk: pr_err("unable to get major %d for misc devices\n", MISC_MAJOR); class_destroy(misc_class); fail_remove: if (ret) remove_proc_entry("misc", NULL); return err; } subsys_initcall(misc_init);