Re: [systemd-devel] [PATCH] backlight: do nothing if max_brightness is 0
Am 23.04.2014 07:00, schrieb Lennart Poettering: > On Thu, 27.03.14 23:41, Thomas Bächler (tho...@archlinux.org) wrote: > >> 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. > > Humm. To me this appears like the driver is broken. The kernel should > not expose a backlight device if there isn't any backend to it? Yes. > Have you > filed a kernel bug? No, I'll take care of it though. > I have changed git now to still print a warning in this case, as we > shouldn't silently tape over broken drivers. Very good. While we should not try to work with nonsense brightness values, a warning is perfectly fine. signature.asc Description: OpenPGP digital signature ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] [PATCH] backlight: do nothing if max_brightness is 0
On Thu, 27.03.14 23:41, Thomas Bächler (tho...@archlinux.org) wrote: > 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. Humm. To me this appears like the driver is broken. The kernel should not expose a backlight device if there isn't any backend to it? Have you filed a kernel bug? I have changed git now to still print a warning in this case, as we shouldn't silently tape over broken drivers. Lennart -- Lennart Poettering, Red Hat ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] [PATCH] backlight: do nothing if max_brightness is 0
On Wed, Apr 2, 2014 at 8:20 PM, Thomas Bächler wrote: > Am 27.03.2014 23:41, schrieb Thomas Bächler: >> 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. Applied. Thanks! Cheers, Tom ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] [PATCH] backlight: do nothing if max_brightness is 0
Am 27.03.2014 23:41, schrieb Thomas Bächler: > 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. Ping? signature.asc Description: OpenPGP digital signature ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
[systemd-devel] [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.
---
Sorry, this diff looks extremely weird, but I couldn't get git-diff
to produce a nicer one.
src/backlight/backlight.c | 44 ++--
1 file changed, 30 insertions(+), 14 deletions(-)
diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
index abf8bcf..ce0385b 100644
--- a/src/backlight/backlight.c
+++ b/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) {
--
1.9.1
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