root/fs/devices.c

/* */

DEFINITIONS

1. get_blkfops
2. get_chrfops
3. register_chrdev
4. register_blkdev
5. unregister_chrdev
6. unregister_blkdev
7. blkdev_open
8. chrdev_open

   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 
   9 #include <linux/fs.h>
  10 #include <linux/major.h>
  11 #include <linux/string.h>
  12 #include <linux/sched.h>
  13 #include <linux/ext_fs.h>
  14 #include <linux/stat.h>
  15 #include <linux/fcntl.h>
  16 #include <linux/errno.h>
  17 
  18 struct device_struct {
  19         const char * name;
  20         struct file_operations * fops;
  21 };
  22 
  23 static struct device_struct chrdevs[MAX_CHRDEV] = {
  24         { NULL, NULL },
  25 };
  26 
  27 static struct device_struct blkdevs[MAX_BLKDEV] = {
  28         { NULL, NULL },
  29 };
  30 
  31 struct file_operations * get_blkfops(unsigned int major)
     /*  */
  32 {
  33         if (major >= MAX_BLKDEV)
  34                 return NULL;
  35         return blkdevs[major].fops;
  36 }
  37 
  38 struct file_operations * get_chrfops(unsigned int major)
     /*  */
  39 {
  40         if (major >= MAX_CHRDEV)
  41                 return NULL;
  42         return chrdevs[major].fops;
  43 }
  44 
  45 int register_chrdev(unsigned int major, const char * name, struct file_operations *fops)
     /*  */
  46 {
  47         if (major >= MAX_CHRDEV)
  48                 return -EINVAL;
  49         if (chrdevs[major].fops)
  50                 return -EBUSY;
  51         chrdevs[major].name = name;
  52         chrdevs[major].fops = fops;
  53         return 0;
  54 }
  55 
  56 int register_blkdev(unsigned int major, const char * name, struct file_operations *fops)
     /*  */
  57 {
  58         if (major >= MAX_BLKDEV)
  59                 return -EINVAL;
  60         if (blkdevs[major].fops)
  61                 return -EBUSY;
  62         blkdevs[major].name = name;
  63         blkdevs[major].fops = fops;
  64         return 0;
  65 }
  66 
  67 int unregister_chrdev(unsigned int major, const char * name)
     /*  */
  68 {
  69         if (major >= MAX_CHRDEV)
  70                 return -EINVAL;
  71         if (!chrdevs[major].fops)
  72                 return -EINVAL;
  73         if (strcmp(chrdevs[major].name, name))
  74                 return -EINVAL;
  75         chrdevs[major].name = NULL;
  76         chrdevs[major].fops = NULL;
  77         return 0;
  78 }
  79 
  80 int unregister_blkdev(unsigned int major, const char * name)
     /*  */
  81 {
  82         if (major >= MAX_BLKDEV)
  83                 return -EINVAL;
  84         if (!blkdevs[major].fops)
  85                 return -EINVAL;
  86         if (strcmp(blkdevs[major].name, name))
  87                 return -EINVAL;
  88         blkdevs[major].name = NULL;
  89         blkdevs[major].fops = NULL;
  90         return 0;
  91 }
  92 
  93 /*
  94  * Called every time a block special file is opened
  95  */
  96 int blkdev_open(struct inode * inode, struct file * filp)
     /*  */
  97 {
  98         int i;
  99 
 100         i = MAJOR(inode->i_rdev);
 101         if (i >= MAX_BLKDEV || !blkdevs[i].fops)
 102                 return -ENODEV;
 103         filp->f_op = blkdevs[i].fops;
 104         if (filp->f_op->open)
 105                 return filp->f_op->open(inode,filp);
 106         return 0;
 107 }       
 108 
 109 /*
 110  * Dummy default file-operations: the only thing this does
 111  * is contain the open that then fills in the correct operations
 112  * depending on the special file...
 113  */
 114 struct file_operations def_blk_fops = {
 115         NULL,           /* lseek */
 116         NULL,           /* read */
 117         NULL,           /* write */
 118         NULL,           /* readdir */
 119         NULL,           /* select */
 120         NULL,           /* ioctl */
 121         NULL,           /* mmap */
 122         blkdev_open,    /* open */
 123         NULL,           /* release */
 124 };
 125 
 126 struct inode_operations blkdev_inode_operations = {
 127         &def_blk_fops,          /* default file operations */
 128         NULL,                   /* create */
 129         NULL,                   /* lookup */
 130         NULL,                   /* link */
 131         NULL,                   /* unlink */
 132         NULL,                   /* symlink */
 133         NULL,                   /* mkdir */
 134         NULL,                   /* rmdir */
 135         NULL,                   /* mknod */
 136         NULL,                   /* rename */
 137         NULL,                   /* readlink */
 138         NULL,                   /* follow_link */
 139         NULL,                   /* bmap */
 140         NULL,                   /* truncate */
 141         NULL                    /* permission */
 142 };
 143 
 144 /*
 145  * Called every time a character special file is opened
 146  */
 147 int chrdev_open(struct inode * inode, struct file * filp)
     /*  */
 148 {
 149         int i;
 150 
 151         i = MAJOR(inode->i_rdev);
 152         if (i >= MAX_CHRDEV || !chrdevs[i].fops)
 153                 return -ENODEV;
 154         filp->f_op = chrdevs[i].fops;
 155         if (filp->f_op->open)
 156                 return filp->f_op->open(inode,filp);
 157         return 0;
 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 struct file_operations def_chr_fops = {
 166         NULL,           /* lseek */
 167         NULL,           /* read */
 168         NULL,           /* write */
 169         NULL,           /* readdir */
 170         NULL,           /* select */
 171         NULL,           /* ioctl */
 172         NULL,           /* mmap */
 173         chrdev_open,    /* open */
 174         NULL,           /* release */
 175 };
 176 
 177 struct inode_operations chrdev_inode_operations = {
 178         &def_chr_fops,          /* default file operations */
 179         NULL,                   /* create */
 180         NULL,                   /* lookup */
 181         NULL,                   /* link */
 182         NULL,                   /* unlink */
 183         NULL,                   /* symlink */
 184         NULL,                   /* mkdir */
 185         NULL,                   /* rmdir */
 186         NULL,                   /* mknod */
 187         NULL,                   /* rename */
 188         NULL,                   /* readlink */
 189         NULL,                   /* follow_link */
 190         NULL,                   /* bmap */
 191         NULL,                   /* truncate */
 192         NULL                    /* permission */
 193 };

/* */