fs/devices.c

   1 /*
   2  *  linux/fs/devices.c
   3  *
   4  * (C) 1993 Matthias Urlichs -- collected common code and tables.
   5  *
   6  *  Copyright (C) 1991, 1992  Linus Torvalds
   7  *
   8  *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
   9  *  (changed to kmod)
  10  */
  11
  12 #include <linux/config.h>
  13 #include <linux/fs.h>
  14 #include <linux/major.h>
  15 #include <linux/string.h>
  16 #include <linux/sched.h>
  17 #include <linux/stat.h>
  18 #include <linux/fcntl.h>
  19 #include <linux/errno.h>
  20 #include <linux/module.h>
  21 #include <linux/smp_lock.h>
  22 #ifdef CONFIG_KMOD
  23 #include <linux/kmod.h>
  24
  25 #include <linux/tty.h>
  26
  27 /* serial module kmod load support */
  28 struct tty_driver *get_tty_driver(kdev_t device);
  29 #define isa_tty_dev(ma) (ma == TTY_MAJOR || ma == TTYAUX_MAJOR)
  30 #define need_serial(ma,mi) (get_tty_driver(MKDEV(ma,mi)) == NULL)
  31 #endif
  32
  33 struct device_struct {
  34         const char * name;
  35         struct file_operations * fops;
  36 };
  37
  38 static rwlock_t chrdevs_lock = RW_LOCK_UNLOCKED;
  39 static struct device_struct chrdevs[MAX_CHRDEV];
  40
  41 extern int get_blkdev_list(char *);
  42
  43 int get_device_list(char * page)
  44 {
  45         int i;
  46         int len;
  47
  48         len = sprintf(page, "Character devices:\n");
  49         read_lock(&chrdevs_lock);
  50         for (i = 0; i < MAX_CHRDEV ; i++) {
  51                 if (chrdevs[i].fops) {
  52                         len += sprintf(page+len, "%3d %s\n", i, chrdevs[i].name);
  53                 }
  54         }
  55         read_unlock(&chrdevs_lock);
  56         len += get_blkdev_list(page+len);
  57         return len;
  58 }
  59
  60 /*
  61         Return the function table of a device.
  62         Load the driver if needed.
  63         Increment the reference count of module in question.
  64 */
  65 static struct file_operations * get_chrfops(unsigned int major, unsigned int minor)
  66 {
  67         struct file_operations *ret = NULL;
  68
  69         if (!major || major >= MAX_CHRDEV)
  70                 return NULL;
  71
  72         read_lock(&chrdevs_lock);
  73         ret = fops_get(chrdevs[major].fops);
  74         read_unlock(&chrdevs_lock);
  75 #ifdef CONFIG_KMOD
  76         if (ret && isa_tty_dev(major)) {
  77                 lock_kernel();
  78                 if (need_serial(major,minor)) {
  79                         /* Force request_module anyway, but what for? */
  80                         fops_put(ret);
  81                         ret = NULL;
  82                 }
  83                 unlock_kernel();
  84         }
  85         if (!ret) {
  86                 char name[20];
  87                 sprintf(name, "char-major-%d", major);
  88                 request_module(name);
  89
  90                 read_lock(&chrdevs_lock);
  91                 ret = fops_get(chrdevs[major].fops);
  92                 read_unlock(&chrdevs_lock);
  93         }
  94 #endif
  95         return ret;
  96 }
  97
  98 int register_chrdev(unsigned int major, const char * name, struct file_operations *fops)
  99 {
 100         if (major == 0) {
 101                 write_lock(&chrdevs_lock);
 102                 for (major = MAX_CHRDEV-1; major > 0; major--) {
 103                         if (chrdevs[major].fops == NULL) {
 104                                 chrdevs[major].name = name;
 105                                 chrdevs[major].fops = fops;
 106                                 write_unlock(&chrdevs_lock);
 107                                 return major;
 108                         }
 109                 }
 110                 write_unlock(&chrdevs_lock);
 111                 return -EBUSY;
 112         }
 113         if (major >= MAX_CHRDEV)
 114                 return -EINVAL;
 115         write_lock(&chrdevs_lock);
 116         if (chrdevs[major].fops && chrdevs[major].fops != fops) {
 117                 write_unlock(&chrdevs_lock);
 118                 return -EBUSY;
 119         }
 120         chrdevs[major].name = name;
 121         chrdevs[major].fops = fops;
 122         write_unlock(&chrdevs_lock);
 123         return 0;
 124 }
 125
 126 int unregister_chrdev(unsigned int major, const char * name)
 127 {
 128         if (major >= MAX_CHRDEV)
 129                 return -EINVAL;
 130         write_lock(&chrdevs_lock);
 131         if (!chrdevs[major].fops || strcmp(chrdevs[major].name, name)) {
 132                 write_unlock(&chrdevs_lock);
 133                 return -EINVAL;
 134         }
 135         chrdevs[major].name = NULL;
 136         chrdevs[major].fops = NULL;
 137         write_unlock(&chrdevs_lock);
 138         return 0;
 139 }
 140
 141 /*
 142  * Called every time a character special file is opened
 143  */
 144 int chrdev_open(struct inode * inode, struct file * filp)
 145 {
 146         int ret = -ENODEV;
 147
 148         filp->f_op = get_chrfops(MAJOR(inode->i_rdev), MINOR(inode->i_rdev));
 149         if (filp->f_op) {
 150                 ret = 0;
 151                 if (filp->f_op->open != NULL) {
 152                         lock_kernel();
 153                         ret = filp->f_op->open(inode,filp);
 154                         unlock_kernel();
 155                 }
 156         }
 157         return ret;
 158 }
 159
 160 /*
 161  * Dummy default file-operations: the only thing this does
 162  * is contain the open that then fills in the correct operations
 163  * depending on the special file...
 164  */
 165 static struct file_operations def_chr_fops = {
 166         open:           chrdev_open,
 167 };
 168
 169 /*
 170  * Print device name (in decimal, hexadecimal or symbolic)
 171  * Note: returns pointer to static data!
 172  */
 173 const char * kdevname(kdev_t dev)
 174 {
 175         static char buffer[32];
 176         sprintf(buffer, "%02x:%02x", MAJOR(dev), MINOR(dev));
 177         return buffer;
 178 }
 179
 180 const char * cdevname(kdev_t dev)
 181 {
 182         static char buffer[32];
 183         const char * name = chrdevs[MAJOR(dev)].name;
 184
 185         if (!name)
 186                 name = "unknown-char";
 187         sprintf(buffer, "%s(%d,%d)", name, MAJOR(dev), MINOR(dev));
 188         return buffer;
 189 }
 190
 191 static int sock_no_open(struct inode *irrelevant, struct file *dontcare)
 192 {
 193         return -ENXIO;
 194 }
 195
 196 static struct file_operations bad_sock_fops = {
 197         open:           sock_no_open
 198 };
 199
 200 void init_special_inode(struct inode *inode, umode_t mode, int rdev)
 201 {
 202         inode->i_mode = mode;
 203         if (S_ISCHR(mode)) {
 204                 inode->i_fop = &def_chr_fops;
 205                 inode->i_rdev = to_kdev_t(rdev);
 206         } else if (S_ISBLK(mode)) {
 207                 inode->i_fop = &def_blk_fops;
 208                 inode->i_rdev = to_kdev_t(rdev);
 209                 inode->i_bdev = bdget(rdev);
 210         } else if (S_ISFIFO(mode))
 211                 inode->i_fop = &def_fifo_fops;
 212         else if (S_ISSOCK(mode))
 213                 inode->i_fop = &bad_sock_fops;
 214         else
 215                 printk(KERN_DEBUG "init_special_inode: bogus imode (%o)\n", mode);
 216 }