return true;
}
+static unsigned get_max_brightness(struct udev_device *device) {
+ int r;
+ const char *max_brightness_str;
+ unsigned max_brightness;
+
+ max_brightness_str = udev_device_get_sysattr_value(device, "max_brightness");
+ if (!max_brightness_str) {
+ log_warning("Failed to read max_brightness attribute");
+ return 0;
+ }
+
+ r = safe_atou(max_brightness_str, &max_brightness);
+ if (r < 0) {
+ log_warning("Failed to parse max_brightness \"%s\": %s", max_brightness_str, strerror(-r));
+ return 0;
+ }
+
+ return max_brightness;
+}
+
+/* Some systems turn the backlight all the way off at the lowest levels.
+ * clamp_brightness clamps the saved brightness to at least 1 or 5% of
+ * max_brightness. This avoids preserving an unreadably dim screen, which
+ * would otherwise force the user to disable state restoration. */
+static void clamp_brightness(struct udev_device *device, char **value, unsigned max_brightness) {
+ int r;
+ unsigned brightness, new_brightness;
+
+ r = safe_atou(*value, &brightness);
+ if (r < 0) {
+ log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r));
+ return;
+ }
+
+ new_brightness = MAX3(brightness, 1U, max_brightness/20);
+ if (new_brightness != brightness) {
+ char *old_value = *value;
+
+ r = asprintf(value, "%u", new_brightness);
+ if (r < 0) {
+ log_oom();
+ return;
+ }
+
+ log_debug("Saved brightness %s too low; increasing to %s.", old_value, *value);
+ free(old_value);
+ }
+}
+
int main(int argc, char *argv[]) {
_cleanup_udev_unref_ struct udev *udev = NULL;
_cleanup_udev_device_unref_ struct udev_device *device = NULL;
_cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
const char *sysname, *path_id;
+ unsigned max_brightness;
int r;
if (argc != 3) {
return EXIT_FAILURE;
}
+ /* If max_brightness is 0, then there is no actual backlight
+ * device. This happens on desktops with Asus mainboards
+ * that load the eeepc-wmi module.
+ */
+ max_brightness = get_max_brightness(device);
+ if (max_brightness == 0)
+ return EXIT_SUCCESS;
+
escaped_ss = cescape(ss);
if (!escaped_ss) {
log_oom();
return EXIT_FAILURE;
}
+ clamp_brightness(device, &value, max_brightness);
+
r = udev_device_set_sysattr_value(device, "brightness", value);
if (r < 0) {
log_error("Failed to write system attribute: %s", strerror(-r));