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 mutex_lock(&misc_mtx); 71 return seq_list_start(&misc_list, *pos); 72 } 73 74 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos) 75 { 76 return seq_list_next(v, &misc_list, pos); 77 } 78 79 static void misc_seq_stop(struct seq_file *seq, void *v) 80 { 81 mutex_unlock(&misc_mtx); 82 } 83 84 static int misc_seq_show(struct seq_file *seq, void *v) 85 { 86 const struct miscdevice *p = list_entry(v, struct miscdevice, list); 87 88 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : ""); 89 return 0; 90 } 91 92 93 static struct seq_operations misc_seq_ops = { 94 .start = misc_seq_start, 95 .next = misc_seq_next, 96 .stop = misc_seq_stop, 97 .show = misc_seq_show, 98 }; 99 100 static int misc_seq_open(struct inode *inode, struct file *file) 101 { 102 return seq_open(file, &misc_seq_ops); 103 } 104 105 static const struct file_operations misc_proc_fops = { 106 .owner = THIS_MODULE, 107 .open = misc_seq_open, 108 .read = seq_read, 109 .llseek = seq_lseek, 110 .release = seq_release, 111 }; 112 #endif 113 114 static int misc_open(struct inode * inode, struct file * file) 115 { 116 int minor = iminor(inode); 117 struct miscdevice *c; 118 int err = -ENODEV; 119 const struct file_operations *old_fops, *new_fops = NULL; 120 121 mutex_lock(&misc_mtx); 122 123 list_for_each_entry(c, &misc_list, list) { 124 if (c->minor == minor) { 125 new_fops = fops_get(c->fops); 126 break; 127 } 128 } 129 130 if (!new_fops) { 131 mutex_unlock(&misc_mtx); 132 request_module("char-major-%d-%d", MISC_MAJOR, minor); 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 if (!new_fops) 142 goto fail; 143 } 144 145 err = 0; 146 old_fops = file->f_op; 147 file->f_op = new_fops; 148 if (file->f_op->open) { 149 err=file->f_op->open(inode,file); 150 if (err) { 151 fops_put(file->f_op); 152 file->f_op = fops_get(old_fops); 153 } 154 } 155 fops_put(old_fops); 156 fail: 157 mutex_unlock(&misc_mtx); 158 return err; 159 } 160 161 static struct class *misc_class; 162 163 static const struct file_operations misc_fops = { 164 .owner = THIS_MODULE, 165 .open = misc_open, 166 }; 167 168 169 /** 170 * misc_register - register a miscellaneous device 171 * @misc: device structure 172 * 173 * Register a miscellaneous device with the kernel. If the minor 174 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned 175 * and placed in the minor field of the structure. For other cases 176 * the minor number requested is used. 177 * 178 * The structure passed is linked into the kernel and may not be 179 * destroyed until it has been unregistered. 180 * 181 * A zero is returned on success and a negative errno code for 182 * failure. 183 */ 184 185 int misc_register(struct miscdevice * misc) 186 { 187 struct miscdevice *c; 188 dev_t dev; 189 int err = 0; 190 191 INIT_LIST_HEAD(&misc->list); 192 193 mutex_lock(&misc_mtx); 194 list_for_each_entry(c, &misc_list, list) { 195 if (c->minor == misc->minor) { 196 mutex_unlock(&misc_mtx); 197 return -EBUSY; 198 } 199 } 200 201 if (misc->minor == MISC_DYNAMIC_MINOR) { 202 int i = DYNAMIC_MINORS; 203 while (--i >= 0) 204 if ( (misc_minors[i>>3] & (1 << (i&7))) == 0) 205 break; 206 if (i<0) { 207 mutex_unlock(&misc_mtx); 208 return -EBUSY; 209 } 210 misc->minor = i; 211 } 212 213 if (misc->minor < DYNAMIC_MINORS) 214 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7); 215 dev = MKDEV(MISC_MAJOR, misc->minor); 216 217 misc->this_device = device_create(misc_class, misc->parent, dev, 218 "%s", misc->name); 219 if (IS_ERR(misc->this_device)) { 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 * @suspended: to be set if the function is used during suspend/resume 238 * 239 * Unregister a miscellaneous device that was previously 240 * successfully registered with misc_register(). Success 241 * is indicated by a zero return, a negative errno code 242 * indicates an error. 243 */ 244 245 int __misc_deregister(struct miscdevice *misc, bool suspended) 246 { 247 int i = misc->minor; 248 249 if (list_empty(&misc->list)) 250 return -EINVAL; 251 252 mutex_lock(&misc_mtx); 253 list_del(&misc->list); 254 if (suspended) 255 destroy_suspended_device(misc_class, 256 MKDEV(MISC_MAJOR, misc->minor)); 257 else 258 device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor)); 259 if (i < DYNAMIC_MINORS && i>0) { 260 misc_minors[i>>3] &= ~(1 << (misc->minor & 7)); 261 } 262 mutex_unlock(&misc_mtx); 263 return 0; 264 } 265 266 EXPORT_SYMBOL(misc_register); 267 EXPORT_SYMBOL(__misc_deregister); 268 269 static int __init misc_init(void) 270 { 271 #ifdef CONFIG_PROC_FS 272 struct proc_dir_entry *ent; 273 274 ent = create_proc_entry("misc", 0, NULL); 275 if (ent) 276 ent->proc_fops = &misc_proc_fops; 277 #endif 278 misc_class = class_create(THIS_MODULE, "misc"); 279 if (IS_ERR(misc_class)) 280 return PTR_ERR(misc_class); 281 282 if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) { 283 printk("unable to get major %d for misc devices\n", 284 MISC_MAJOR); 285 class_destroy(misc_class); 286 return -EIO; 287 } 288 return 0; 289 } 290 subsys_initcall(misc_init); 291