misc.c 6.6 KB

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  1. /*
  2. * linux/drivers/char/misc.c
  3. *
  4. * Generic misc open routine by Johan Myreen
  5. *
  6. * Based on code from Linus
  7. *
  8. * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
  9. * changes incorporated into 0.97pl4
  10. * by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
  11. * See busmouse.c for particulars.
  12. *
  13. * Made things a lot mode modular - easy to compile in just one or two
  14. * of the misc drivers, as they are now completely independent. Linus.
  15. *
  16. * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
  17. *
  18. * Fixed a failing symbol register to free the device registration
  19. * Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
  20. *
  21. * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
  22. *
  23. * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
  24. *
  25. * Handling of mouse minor numbers for kerneld:
  26. * Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
  27. * adapted by Bjorn Ekwall <bj0rn@blox.se>
  28. * corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
  29. *
  30. * Changes for kmod (from kerneld):
  31. * Cyrus Durgin <cider@speakeasy.org>
  32. *
  33. * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au> 10-Jan-1998
  34. */
  35. #include <linux/module.h>
  36. #include <linux/fs.h>
  37. #include <linux/errno.h>
  38. #include <linux/miscdevice.h>
  39. #include <linux/kernel.h>
  40. #include <linux/major.h>
  41. #include <linux/slab.h>
  42. #include <linux/proc_fs.h>
  43. #include <linux/seq_file.h>
  44. #include <linux/stat.h>
  45. #include <linux/init.h>
  46. #include <linux/device.h>
  47. #include <linux/tty.h>
  48. #include <linux/kmod.h>
  49. /*
  50. * Head entry for the doubly linked miscdevice list
  51. */
  52. static LIST_HEAD(misc_list);
  53. static DECLARE_MUTEX(misc_sem);
  54. /*
  55. * Assigned numbers, used for dynamic minors
  56. */
  57. #define DYNAMIC_MINORS 64 /* like dynamic majors */
  58. static unsigned char misc_minors[DYNAMIC_MINORS / 8];
  59. extern int pmu_device_init(void);
  60. #ifdef CONFIG_PROC_FS
  61. static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  62. {
  63. struct miscdevice *p;
  64. loff_t off = 0;
  65. down(&misc_sem);
  66. list_for_each_entry(p, &misc_list, list) {
  67. if (*pos == off++)
  68. return p;
  69. }
  70. return NULL;
  71. }
  72. static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  73. {
  74. struct list_head *n = ((struct miscdevice *)v)->list.next;
  75. ++*pos;
  76. return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  77. : NULL;
  78. }
  79. static void misc_seq_stop(struct seq_file *seq, void *v)
  80. {
  81. up(&misc_sem);
  82. }
  83. static int misc_seq_show(struct seq_file *seq, void *v)
  84. {
  85. const struct miscdevice *p = v;
  86. seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
  87. return 0;
  88. }
  89. static struct seq_operations misc_seq_ops = {
  90. .start = misc_seq_start,
  91. .next = misc_seq_next,
  92. .stop = misc_seq_stop,
  93. .show = misc_seq_show,
  94. };
  95. static int misc_seq_open(struct inode *inode, struct file *file)
  96. {
  97. return seq_open(file, &misc_seq_ops);
  98. }
  99. static const struct file_operations misc_proc_fops = {
  100. .owner = THIS_MODULE,
  101. .open = misc_seq_open,
  102. .read = seq_read,
  103. .llseek = seq_lseek,
  104. .release = seq_release,
  105. };
  106. #endif
  107. static int misc_open(struct inode * inode, struct file * file)
  108. {
  109. int minor = iminor(inode);
  110. struct miscdevice *c;
  111. int err = -ENODEV;
  112. const struct file_operations *old_fops, *new_fops = NULL;
  113. down(&misc_sem);
  114. list_for_each_entry(c, &misc_list, list) {
  115. if (c->minor == minor) {
  116. new_fops = fops_get(c->fops);
  117. break;
  118. }
  119. }
  120. if (!new_fops) {
  121. up(&misc_sem);
  122. request_module("char-major-%d-%d", MISC_MAJOR, minor);
  123. down(&misc_sem);
  124. list_for_each_entry(c, &misc_list, list) {
  125. if (c->minor == minor) {
  126. new_fops = fops_get(c->fops);
  127. break;
  128. }
  129. }
  130. if (!new_fops)
  131. goto fail;
  132. }
  133. err = 0;
  134. old_fops = file->f_op;
  135. file->f_op = new_fops;
  136. if (file->f_op->open) {
  137. err=file->f_op->open(inode,file);
  138. if (err) {
  139. fops_put(file->f_op);
  140. file->f_op = fops_get(old_fops);
  141. }
  142. }
  143. fops_put(old_fops);
  144. fail:
  145. up(&misc_sem);
  146. return err;
  147. }
  148. static struct class *misc_class;
  149. static const struct file_operations misc_fops = {
  150. .owner = THIS_MODULE,
  151. .open = misc_open,
  152. };
  153. /**
  154. * misc_register - register a miscellaneous device
  155. * @misc: device structure
  156. *
  157. * Register a miscellaneous device with the kernel. If the minor
  158. * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
  159. * and placed in the minor field of the structure. For other cases
  160. * the minor number requested is used.
  161. *
  162. * The structure passed is linked into the kernel and may not be
  163. * destroyed until it has been unregistered.
  164. *
  165. * A zero is returned on success and a negative errno code for
  166. * failure.
  167. */
  168. int misc_register(struct miscdevice * misc)
  169. {
  170. struct miscdevice *c;
  171. dev_t dev;
  172. int err = 0;
  173. INIT_LIST_HEAD(&misc->list);
  174. down(&misc_sem);
  175. list_for_each_entry(c, &misc_list, list) {
  176. if (c->minor == misc->minor) {
  177. up(&misc_sem);
  178. return -EBUSY;
  179. }
  180. }
  181. if (misc->minor == MISC_DYNAMIC_MINOR) {
  182. int i = DYNAMIC_MINORS;
  183. while (--i >= 0)
  184. if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
  185. break;
  186. if (i<0) {
  187. up(&misc_sem);
  188. return -EBUSY;
  189. }
  190. misc->minor = i;
  191. }
  192. if (misc->minor < DYNAMIC_MINORS)
  193. misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
  194. dev = MKDEV(MISC_MAJOR, misc->minor);
  195. misc->this_device = device_create(misc_class, misc->parent, dev,
  196. "%s", misc->name);
  197. if (IS_ERR(misc->this_device)) {
  198. err = PTR_ERR(misc->this_device);
  199. goto out;
  200. }
  201. /*
  202. * Add it to the front, so that later devices can "override"
  203. * earlier defaults
  204. */
  205. list_add(&misc->list, &misc_list);
  206. out:
  207. up(&misc_sem);
  208. return err;
  209. }
  210. /**
  211. * misc_deregister - unregister a miscellaneous device
  212. * @misc: device to unregister
  213. *
  214. * Unregister a miscellaneous device that was previously
  215. * successfully registered with misc_register(). Success
  216. * is indicated by a zero return, a negative errno code
  217. * indicates an error.
  218. */
  219. int misc_deregister(struct miscdevice * misc)
  220. {
  221. int i = misc->minor;
  222. if (list_empty(&misc->list))
  223. return -EINVAL;
  224. down(&misc_sem);
  225. list_del(&misc->list);
  226. device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
  227. if (i < DYNAMIC_MINORS && i>0) {
  228. misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
  229. }
  230. up(&misc_sem);
  231. return 0;
  232. }
  233. EXPORT_SYMBOL(misc_register);
  234. EXPORT_SYMBOL(misc_deregister);
  235. static int __init misc_init(void)
  236. {
  237. #ifdef CONFIG_PROC_FS
  238. struct proc_dir_entry *ent;
  239. ent = create_proc_entry("misc", 0, NULL);
  240. if (ent)
  241. ent->proc_fops = &misc_proc_fops;
  242. #endif
  243. misc_class = class_create(THIS_MODULE, "misc");
  244. if (IS_ERR(misc_class))
  245. return PTR_ERR(misc_class);
  246. if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
  247. printk("unable to get major %d for misc devices\n",
  248. MISC_MAJOR);
  249. class_destroy(misc_class);
  250. return -EIO;
  251. }
  252. return 0;
  253. }
  254. subsys_initcall(misc_init);