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