fs/proc/devices.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/fs.h>
   3 #include <linux/init.h>
   4 #include <linux/proc_fs.h>
   5 #include <linux/seq_file.h>
   6
   7 static int devinfo_show(struct seq_file *f, void *v)
   8 {
   9         int i = *(loff_t *) v;
  10
  11         if (i < CHRDEV_MAJOR_MAX) {
  12                 if (i == 0)
  13                         seq_puts(f, "Character devices:\n");
  14                 chrdev_show(f, i);
  15         }
  16 #ifdef CONFIG_BLOCK
  17         else {
  18                 i -= CHRDEV_MAJOR_MAX;
  19                 if (i == 0)
  20                         seq_puts(f, "\nBlock devices:\n");
  21                 blkdev_show(f, i);
  22         }
  23 #endif
  24         return 0;
  25 }
  26
  27 static void *devinfo_start(struct seq_file *f, loff_t *pos)
  28 {
  29         if (*pos < (BLKDEV_MAJOR_MAX + CHRDEV_MAJOR_MAX))
  30                 return pos;
  31         return NULL;
  32 }
  33
  34 static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos)
  35 {
  36         (*pos)++;
  37         if (*pos >= (BLKDEV_MAJOR_MAX + CHRDEV_MAJOR_MAX))
  38                 return NULL;
  39         return pos;
  40 }
  41
  42 static void devinfo_stop(struct seq_file *f, void *v)
  43 {
  44         /* Nothing to do */
  45 }
  46
  47 static const struct seq_operations devinfo_ops = {
  48         .start = devinfo_start,
  49         .next  = devinfo_next,
  50         .stop  = devinfo_stop,
  51         .show  = devinfo_show
  52 };
  53
  54 static int devinfo_open(struct inode *inode, struct file *filp)
  55 {
  56         return seq_open(filp, &devinfo_ops);
  57 }
  58
  59 static const struct file_operations proc_devinfo_operations = {
  60         .open           = devinfo_open,
  61         .read           = seq_read,
  62         .llseek         = seq_lseek,
  63         .release        = seq_release,
  64 };
  65
  66 static int __init proc_devices_init(void)
  67 {
  68         proc_create("devices", 0, NULL, &proc_devinfo_operations);
  69         return 0;
  70 }
  71 fs_initcall(proc_devices_init);