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/mutex.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 #include <linux/gfp.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 DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS); 64 65 #ifdef CONFIG_PROC_FS misc_seq_start(struct seq_file * seq,loff_t * pos)66 static void *misc_seq_start(struct seq_file *seq, loff_t *pos) 67 { 68 mutex_lock(&misc_mtx); 69 return seq_list_start(&misc_list, *pos); 70 } 71 misc_seq_next(struct seq_file * seq,void * v,loff_t * pos)72 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos) 73 { 74 return seq_list_next(v, &misc_list, pos); 75 } 76 misc_seq_stop(struct seq_file * seq,void * v)77 static void misc_seq_stop(struct seq_file *seq, void *v) 78 { 79 mutex_unlock(&misc_mtx); 80 } 81 misc_seq_show(struct seq_file * seq,void * v)82 static int misc_seq_show(struct seq_file *seq, void *v) 83 { 84 const struct miscdevice *p = list_entry(v, struct miscdevice, list); 85 86 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : ""); 87 return 0; 88 } 89 90 91 static const struct seq_operations misc_seq_ops = { 92 .start = misc_seq_start, 93 .next = misc_seq_next, 94 .stop = misc_seq_stop, 95 .show = misc_seq_show, 96 }; 97 misc_seq_open(struct inode * inode,struct file * file)98 static int misc_seq_open(struct inode *inode, struct file *file) 99 { 100 return seq_open(file, &misc_seq_ops); 101 } 102 103 static const struct file_operations misc_proc_fops = { 104 .owner = THIS_MODULE, 105 .open = misc_seq_open, 106 .read = seq_read, 107 .llseek = seq_lseek, 108 .release = seq_release, 109 }; 110 #endif 111 misc_open(struct inode * inode,struct file * file)112 static int misc_open(struct inode * inode, struct file * file) 113 { 114 int minor = iminor(inode); 115 struct miscdevice *c; 116 int err = -ENODEV; 117 const struct file_operations *old_fops, *new_fops = NULL; 118 119 mutex_lock(&misc_mtx); 120 121 list_for_each_entry(c, &misc_list, list) { 122 if (c->minor == minor) { 123 new_fops = fops_get(c->fops); 124 break; 125 } 126 } 127 128 if (!new_fops) { 129 mutex_unlock(&misc_mtx); 130 request_module("char-major-%d-%d", MISC_MAJOR, minor); 131 mutex_lock(&misc_mtx); 132 133 list_for_each_entry(c, &misc_list, list) { 134 if (c->minor == minor) { 135 new_fops = fops_get(c->fops); 136 break; 137 } 138 } 139 if (!new_fops) 140 goto fail; 141 } 142 143 err = 0; 144 old_fops = file->f_op; 145 file->f_op = new_fops; 146 if (file->f_op->open) { 147 file->private_data = c; 148 err=file->f_op->open(inode,file); 149 if (err) { 150 fops_put(file->f_op); 151 file->f_op = fops_get(old_fops); 152 } 153 } 154 fops_put(old_fops); 155 fail: 156 mutex_unlock(&misc_mtx); 157 return err; 158 } 159 160 static struct class *misc_class; 161 162 static const struct file_operations misc_fops = { 163 .owner = THIS_MODULE, 164 .open = misc_open, 165 .llseek = noop_llseek, 166 }; 167 168 /** 169 * misc_register - register a miscellaneous device 170 * @misc: device structure 171 * 172 * Register a miscellaneous device with the kernel. If the minor 173 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned 174 * and placed in the minor field of the structure. For other cases 175 * the minor number requested is used. 176 * 177 * The structure passed is linked into the kernel and may not be 178 * destroyed until it has been unregistered. 179 * 180 * A zero is returned on success and a negative errno code for 181 * failure. 182 */ 183 misc_register(struct miscdevice * misc)184 int misc_register(struct miscdevice * misc) 185 { 186 dev_t dev; 187 int err = 0; 188 189 INIT_LIST_HEAD(&misc->list); 190 191 mutex_lock(&misc_mtx); 192 193 if (misc->minor == MISC_DYNAMIC_MINOR) { 194 int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS); 195 if (i >= DYNAMIC_MINORS) { 196 mutex_unlock(&misc_mtx); 197 return -EBUSY; 198 } 199 misc->minor = DYNAMIC_MINORS - i - 1; 200 set_bit(i, misc_minors); 201 } else { 202 struct miscdevice *c; 203 204 list_for_each_entry(c, &misc_list, list) { 205 if (c->minor == misc->minor) { 206 mutex_unlock(&misc_mtx); 207 return -EBUSY; 208 } 209 } 210 } 211 212 dev = MKDEV(MISC_MAJOR, misc->minor); 213 214 misc->this_device = device_create(misc_class, misc->parent, dev, 215 misc, "%s", misc->name); 216 if (IS_ERR(misc->this_device)) { 217 int i = DYNAMIC_MINORS - misc->minor - 1; 218 if (i < DYNAMIC_MINORS && i >= 0) 219 clear_bit(i, misc_minors); 220 err = PTR_ERR(misc->this_device); 221 goto out; 222 } 223 224 /* 225 * Add it to the front, so that later devices can "override" 226 * earlier defaults 227 */ 228 list_add(&misc->list, &misc_list); 229 out: 230 mutex_unlock(&misc_mtx); 231 return err; 232 } 233 234 /** 235 * misc_deregister - unregister a miscellaneous device 236 * @misc: device to unregister 237 * 238 * Unregister a miscellaneous device that was previously 239 * successfully registered with misc_register(). Success 240 * is indicated by a zero return, a negative errno code 241 * indicates an error. 242 */ 243 misc_deregister(struct miscdevice * misc)244 int misc_deregister(struct miscdevice *misc) 245 { 246 int i = DYNAMIC_MINORS - misc->minor - 1; 247 248 if (WARN_ON(list_empty(&misc->list))) 249 return -EINVAL; 250 251 mutex_lock(&misc_mtx); 252 list_del(&misc->list); 253 device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor)); 254 if (i < DYNAMIC_MINORS && i >= 0) 255 clear_bit(i, misc_minors); 256 mutex_unlock(&misc_mtx); 257 return 0; 258 } 259 260 EXPORT_SYMBOL(misc_register); 261 EXPORT_SYMBOL(misc_deregister); 262 misc_devnode(struct device * dev,umode_t * mode)263 static char *misc_devnode(struct device *dev, umode_t *mode) 264 { 265 struct miscdevice *c = dev_get_drvdata(dev); 266 267 if (mode && c->mode) 268 *mode = c->mode; 269 if (c->nodename) 270 return kstrdup(c->nodename, GFP_KERNEL); 271 return NULL; 272 } 273 misc_init(void)274 static int __init misc_init(void) 275 { 276 int err; 277 278 #ifdef CONFIG_PROC_FS 279 proc_create("misc", 0, NULL, &misc_proc_fops); 280 #endif 281 misc_class = class_create(THIS_MODULE, "misc"); 282 err = PTR_ERR(misc_class); 283 if (IS_ERR(misc_class)) 284 goto fail_remove; 285 286 err = -EIO; 287 if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) 288 goto fail_printk; 289 misc_class->devnode = misc_devnode; 290 return 0; 291 292 fail_printk: 293 printk("unable to get major %d for misc devices\n", MISC_MAJOR); 294 class_destroy(misc_class); 295 fail_remove: 296 remove_proc_entry("misc", NULL); 297 return err; 298 } 299 subsys_initcall(misc_init); 300