components/backlight.c

   1 /* See LICENSE file for copyright and license details. */
   2 #include "../util.h"
   3
   4 #if defined(__linux__)
   5         #include <limits.h>
   6
   7         #define BRIGHTNESS_MAX "/sys/class/backlight/%s/max_brightness"
   8         #define BRIGHTNESS_CUR "/sys/class/backlight/%s/brightness"
   9
  10         const char *
  11         backlight_perc(const char *card)
  12         {
  13                 char path[PATH_MAX];
  14                 int max, cur;
  15
  16                 if (esnprintf(path, sizeof (path), BRIGHTNESS_MAX, card) < 0 ||
  17                         pscanf(path, "%d", &max) != 1) {
  18                         return NULL;
  19                 }
  20
  21                 if (esnprintf(path, sizeof (path), BRIGHTNESS_CUR, card) < 0 ||
  22                         pscanf(path, "%d", &cur) != 1) {
  23                         return NULL;
  24                 }
  25
  26                 if (max == 0) {
  27                         return NULL;
  28                 }
  29
  30                 return bprintf("%d", cur * 100 / max);
  31         }
  32 #endif