systemd/0002-backlight-do-nothing-if-max_brightness-is-0.patch

109 lines
4.5 KiB
Diff

From 3cadce7d33e263ec7a6a83c00c11144930258b22 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20B=C3=A4chler?= <thomas@archlinux.org>
Date: Thu, 27 Mar 2014 23:41:59 +0100
Subject: [PATCH] backlight: do nothing if max_brightness is 0
On virtually any newer Asus mainboard, the eeepc-wmi driver is loaded.
It exposes a backlight device despite the lack of any physical backlight
devices. This fake backlight device has max_brightness set to 0. Since
the introduction of the clamp_brightness function, systemd-backlight
tries to write '1' to brightness and fails.
This patch changes systemd-backlight to exit gracefully when
max_brightness is 0 before performing any action. This affects
both the load and save actions.
---
src/backlight/backlight.c | 44 ++++++++++++++++++++++++++++++--------------
1 file changed, 30 insertions(+), 14 deletions(-)
diff --git src/backlight/backlight.c src/backlight/backlight.c
index abf8bcf..ce0385b 100644
--- src/backlight/backlight.c
+++ src/backlight/backlight.c
@@ -192,30 +192,37 @@ static bool validate_device(struct udev *udev, struct udev_device *device) {
return true;
}
-/* 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) {
+static unsigned get_max_brightness(struct udev_device *device) {
int r;
const char *max_brightness_str;
- unsigned brightness, max_brightness, new_brightness;
+ 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; not checking saved brightness");
- return;
+ log_warning("Failed to read max_brightness attribute");
+ return 0;
}
- r = safe_atou(*value, &brightness);
+ r = safe_atou(max_brightness_str, &max_brightness);
if (r < 0) {
- log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r));
- return;
+ log_warning("Failed to parse max_brightness \"%s\": %s", max_brightness_str, strerror(-r));
+ return 0;
}
- r = safe_atou(max_brightness_str, &max_brightness);
+ 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 max_brightness \"%s\": %s", max_brightness_str, strerror(-r));
+ log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r));
return;
}
@@ -239,6 +246,7 @@ int main(int argc, char *argv[]) {
_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) {
@@ -294,6 +302,14 @@ int main(int argc, char *argv[]) {
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();
@@ -348,7 +364,7 @@ int main(int argc, char *argv[]) {
return EXIT_FAILURE;
}
- clamp_brightness(device, &value);
+ clamp_brightness(device, &value, max_brightness);
r = udev_device_set_sysattr_value(device, "brightness", value);
if (r < 0) {
--
1.7.9.2