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systemd/0005-backlight-Do-not-clamp-brightness-for-LEDs.patch

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From 4cd2b2cf8ca585d15ebc859701b346658262b5bb Mon Sep 17 00:00:00 2001
From: Denis Tikhomirov <dvtikhomirov@gmail.com>
Date: Thu, 5 Jun 2014 23:59:40 +0400
Subject: [PATCH] backlight: Do not clamp brightness for LEDs
https://bugs.freedesktop.org/show_bug.cgi?id=77092
On Thu, Jun 05, 2014 at 08:37:20AM +0200, Lennart Poettering wrote:
> The patch is line-broken, please send an uncorrupted patch!
I am very sorry, I forgot that my client limits line width. I will use
mutt now on.
> clamp_brightness() clamps the brightness value to the range of the
> actual device. This is a recent addition that was added to deal with
> driver updates where the resolution is changed. I don't think this part
> should be dropped for LED devices. The clamp_brightness() call hence
> should be called unconditionally, however, internally it should use a
> different min_brightness value if something is an !backlight devices...
Thank you for explanation, this sounds very reasonable to me. Please,
see updated patch:
---
src/backlight/backlight.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git src/backlight/backlight.c src/backlight/backlight.c
index 691472c..4d94ebf 100644
--- src/backlight/backlight.c
+++ src/backlight/backlight.c
@@ -225,11 +225,13 @@ static unsigned get_max_brightness(struct udev_device *device) {
/* 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. */
+ * max_brightness in case of 'backlight' subsystem. 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, min_brightness;
+ const char *subsystem;
r = safe_atou(*value, &brightness);
if (r < 0) {
@@ -237,7 +239,12 @@ static void clamp_brightness(struct udev_device *device, char **value, unsigned
return;
}
- min_brightness = MAX(1U, max_brightness/20);
+ subsystem = udev_device_get_subsystem(device);
+ if (streq_ptr(subsystem, "backlight"))
+ min_brightness = MAX(1U, max_brightness/20);
+ else
+ min_brightness = 0;
+
new_brightness = CLAMP(brightness, min_brightness, max_brightness);
if (new_brightness != brightness) {
char *old_value = *value;
--
1.7.9.2