/* returns a value between 0-255 range, where higher is brighter */
static uint32_t
get_normalized_backlight(struct backlight *backlight)
{
long brightness, max_brightness;
long norm;
brightness = backlight_get_brightness(backlight);
max_brightness = backlight_get_max_brightness(backlight);
/* convert it to a scale of 0 to 255 */
norm = (brightness * 255)/(max_brightness);
return (int) norm;
}
long backlight_set_brightness(struct backlight *backlight, long brightness)
{
char *path;
char *buffer = NULL;
int fd;
long ret;
if (asprintf(&path, "%s/%s", backlight->path, "brightness") < 0)
return -ENOMEM;
fd = open(path, O_RDWR);
if (fd < 0) {
ret = -1;
goto out;
}
ret = read(fd, &buffer, sizeof(buffer));
if (ret < 1) {
ret = -1;
goto out;
}
if (asprintf(&buffer, "%ld", brightness) < 0) {
ret = -1;
goto out;
}
ret = write(fd, buffer, strlen(buffer));
if (ret < 0) {
ret = -1;
goto out;
}
ret = backlight_get_brightness(backlight);
backlight->brightness = ret;
out:
if (buffer)
free(buffer);
if (path)
free(path);
close(fd);
return ret;
}
static void
set_backlight(struct udev_device *drm_device, int connector_id, int blight)
{
int connector_type;
long max_brightness, brightness, actual_brightness;
struct backlight *backlight;
long new_blight;
connector_type = get_drm_connector_type(drm_device, connector_id);
if (connector_type < 0)
return;
backlight = backlight_init(drm_device, connector_type);
if (!backlight) {
printf("backlight adjust failed\n");
return;
}
max_brightness = backlight_get_max_brightness(backlight);
printf("Max backlight: %ld\n", max_brightness);
brightness = backlight_get_brightness(backlight);
printf("Cached backlight: %ld\n", brightness);
actual_brightness = backlight_get_actual_brightness(backlight);
printf("Hardware backlight: %ld\n", actual_brightness);
printf("normalized current brightness: %d\n",
get_normalized_backlight(backlight));
/* denormalized value */
new_blight = (blight * max_brightness) / 255;
backlight_set_brightness(backlight, new_blight);
printf("Setting brightness to: %ld (norm: %d)\n", new_blight, blight);
backlight_destroy(backlight);
}
