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 #include <linux/blkdev.h>
   7
   8 static int devinfo_show(struct seq_file *f, void *v)
   9 {
  10         int i = *(loff_t *) v;
  11
  12         if (i < CHRDEV_MAJOR_MAX) {
  13                 if (i == 0)
  14                         seq_puts(f, "Character devices:\n");
  15                 chrdev_show(f, i);
  16         }
  17 #ifdef CONFIG_BLOCK
  18         else {
  19                 i -= CHRDEV_MAJOR_MAX;
  20                 if (i == 0)
  21                         seq_puts(f, "\nBlock devices:\n");
  22                 blkdev_show(f, i);
  23         }
  24 #endif
  25         return 0;
  26 }
  27
  28 static void *devinfo_start(struct seq_file *f, loff_t *pos)
  29 {
  30         if (*pos < (BLKDEV_MAJOR_MAX + CHRDEV_MAJOR_MAX))
  31                 return pos;
  32         return NULL;
  33 }
  34
  35 static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos)
  36 {
  37         (*pos)++;
  38         if (*pos >= (BLKDEV_MAJOR_MAX + CHRDEV_MAJOR_MAX))
  39                 return NULL;
  40         return pos;
  41 }
  42
  43 static void devinfo_stop(struct seq_file *f, void *v)
  44 {
  45         /* Nothing to do */
  46 }
  47
  48 static const struct seq_operations devinfo_ops = {
  49         .start = devinfo_start,
  50         .next  = devinfo_next,
  51         .stop  = devinfo_stop,
  52         .show  = devinfo_show
  53 };
  54
  55 static int __init proc_devices_init(void)
  56 {
  57         proc_create_seq("devices", 0, NULL, &devinfo_ops);
  58         return 0;
  59 }
  60 fs_initcall(proc_devices_init);