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