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 36 #include <linux/module.h> 37 #include <linux/config.h> 38 39 #include <linux/fs.h> 40 #include <linux/errno.h> 41 #include <linux/miscdevice.h> 42 #include <linux/kernel.h> 43 #include <linux/major.h> 44 #include <linux/slab.h> 45 #include <linux/proc_fs.h> 46 #include <linux/seq_file.h> 47 #include <linux/devfs_fs_kernel.h> 48 #include <linux/stat.h> 49 #include <linux/init.h> 50 #include <linux/device.h> 51 #include <linux/tty.h> 52 #include <linux/kmod.h> 53 54 /* 55 * Head entry for the doubly linked miscdevice list 56 */ 57 static LIST_HEAD(misc_list); 58 static DECLARE_MUTEX(misc_sem); 59 60 /* 61 * Assigned numbers, used for dynamic minors 62 */ 63 #define DYNAMIC_MINORS 64 /* like dynamic majors */ 64 static unsigned char misc_minors[DYNAMIC_MINORS / 8]; 65 66 extern int pmu_device_init(void); 67 68 #ifdef CONFIG_PROC_FS 69 static void *misc_seq_start(struct seq_file *seq, loff_t *pos) 70 { 71 struct miscdevice *p; 72 loff_t off = 0; 73 74 down(&misc_sem); 75 list_for_each_entry(p, &misc_list, list) { 76 if (*pos == off++) 77 return p; 78 } 79 return NULL; 80 } 81 82 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos) 83 { 84 struct list_head *n = ((struct miscdevice *)v)->list.next; 85 86 ++*pos; 87 88 return (n != &misc_list) ? list_entry(n, struct miscdevice, list) 89 : NULL; 90 } 91 92 static void misc_seq_stop(struct seq_file *seq, void *v) 93 { 94 up(&misc_sem); 95 } 96 97 static int misc_seq_show(struct seq_file *seq, void *v) 98 { 99 const struct miscdevice *p = v; 100 101 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : ""); 102 return 0; 103 } 104 105 106 static struct seq_operations misc_seq_ops = { 107 .start = misc_seq_start, 108 .next = misc_seq_next, 109 .stop = misc_seq_stop, 110 .show = misc_seq_show, 111 }; 112 113 static int misc_seq_open(struct inode *inode, struct file *file) 114 { 115 return seq_open(file, &misc_seq_ops); 116 } 117 118 static struct file_operations misc_proc_fops = { 119 .owner = THIS_MODULE, 120 .open = misc_seq_open, 121 .read = seq_read, 122 .llseek = seq_lseek, 123 .release = seq_release, 124 }; 125 #endif 126 127 static int misc_open(struct inode * inode, struct file * file) 128 { 129 int minor = iminor(inode); 130 struct miscdevice *c; 131 int err = -ENODEV; 132 const struct file_operations *old_fops, *new_fops = NULL; 133 134 down(&misc_sem); 135 136 list_for_each_entry(c, &misc_list, list) { 137 if (c->minor == minor) { 138 new_fops = fops_get(c->fops); 139 break; 140 } 141 } 142 143 if (!new_fops) { 144 up(&misc_sem); 145 request_module("char-major-%d-%d", MISC_MAJOR, minor); 146 down(&misc_sem); 147 148 list_for_each_entry(c, &misc_list, list) { 149 if (c->minor == minor) { 150 new_fops = fops_get(c->fops); 151 break; 152 } 153 } 154 if (!new_fops) 155 goto fail; 156 } 157 158 err = 0; 159 old_fops = file->f_op; 160 file->f_op = new_fops; 161 if (file->f_op->open) { 162 err=file->f_op->open(inode,file); 163 if (err) { 164 fops_put(file->f_op); 165 file->f_op = fops_get(old_fops); 166 } 167 } 168 fops_put(old_fops); 169 fail: 170 up(&misc_sem); 171 return err; 172 } 173 174 /* 175 * TODO for 2.7: 176 * - add a struct kref to struct miscdevice and make all usages of 177 * them dynamic. 178 */ 179 static struct class *misc_class; 180 181 static struct file_operations misc_fops = { 182 .owner = THIS_MODULE, 183 .open = misc_open, 184 }; 185 186 187 /** 188 * misc_register - register a miscellaneous device 189 * @misc: device structure 190 * 191 * Register a miscellaneous device with the kernel. If the minor 192 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned 193 * and placed in the minor field of the structure. For other cases 194 * the minor number requested is used. 195 * 196 * The structure passed is linked into the kernel and may not be 197 * destroyed until it has been unregistered. 198 * 199 * A zero is returned on success and a negative errno code for 200 * failure. 201 */ 202 203 int misc_register(struct miscdevice * misc) 204 { 205 struct miscdevice *c; 206 dev_t dev; 207 int err; 208 209 down(&misc_sem); 210 list_for_each_entry(c, &misc_list, list) { 211 if (c->minor == misc->minor) { 212 up(&misc_sem); 213 return -EBUSY; 214 } 215 } 216 217 if (misc->minor == MISC_DYNAMIC_MINOR) { 218 int i = DYNAMIC_MINORS; 219 while (--i >= 0) 220 if ( (misc_minors[i>>3] & (1 << (i&7))) == 0) 221 break; 222 if (i<0) { 223 up(&misc_sem); 224 return -EBUSY; 225 } 226 misc->minor = i; 227 } 228 229 if (misc->minor < DYNAMIC_MINORS) 230 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7); 231 if (misc->devfs_name[0] == '\0') { 232 snprintf(misc->devfs_name, sizeof(misc->devfs_name), 233 "misc/%s", misc->name); 234 } 235 dev = MKDEV(MISC_MAJOR, misc->minor); 236 237 misc->class = class_device_create(misc_class, NULL, dev, misc->dev, 238 "%s", misc->name); 239 if (IS_ERR(misc->class)) { 240 err = PTR_ERR(misc->class); 241 goto out; 242 } 243 244 err = devfs_mk_cdev(dev, S_IFCHR|S_IRUSR|S_IWUSR|S_IRGRP, 245 misc->devfs_name); 246 if (err) { 247 class_device_destroy(misc_class, dev); 248 goto out; 249 } 250 251 /* 252 * Add it to the front, so that later devices can "override" 253 * earlier defaults 254 */ 255 list_add(&misc->list, &misc_list); 256 out: 257 up(&misc_sem); 258 return err; 259 } 260 261 /** 262 * misc_deregister - unregister a miscellaneous device 263 * @misc: device to unregister 264 * 265 * Unregister a miscellaneous device that was previously 266 * successfully registered with misc_register(). Success 267 * is indicated by a zero return, a negative errno code 268 * indicates an error. 269 */ 270 271 int misc_deregister(struct miscdevice * misc) 272 { 273 int i = misc->minor; 274 275 if (list_empty(&misc->list)) 276 return -EINVAL; 277 278 down(&misc_sem); 279 list_del(&misc->list); 280 class_device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor)); 281 devfs_remove(misc->devfs_name); 282 if (i < DYNAMIC_MINORS && i>0) { 283 misc_minors[i>>3] &= ~(1 << (misc->minor & 7)); 284 } 285 up(&misc_sem); 286 return 0; 287 } 288 289 EXPORT_SYMBOL(misc_register); 290 EXPORT_SYMBOL(misc_deregister); 291 292 static int __init misc_init(void) 293 { 294 #ifdef CONFIG_PROC_FS 295 struct proc_dir_entry *ent; 296 297 ent = create_proc_entry("misc", 0, NULL); 298 if (ent) 299 ent->proc_fops = &misc_proc_fops; 300 #endif 301 misc_class = class_create(THIS_MODULE, "misc"); 302 if (IS_ERR(misc_class)) 303 return PTR_ERR(misc_class); 304 305 if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) { 306 printk("unable to get major %d for misc devices\n", 307 MISC_MAJOR); 308 class_destroy(misc_class); 309 return -EIO; 310 } 311 return 0; 312 } 313 subsys_initcall(misc_init); 314