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