80 lines
3.0 KiB
Diff
80 lines
3.0 KiB
Diff
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From 7b909d7407965c03caaba30daae7aee113627a83 Mon Sep 17 00:00:00 2001
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From: Josh Triplett <josh@joshtriplett.org>
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Date: Tue, 11 Mar 2014 21:16:33 -0700
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Subject: [PATCH] backlight: Avoid restoring brightness to an unreadably dim
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level
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Some systems turn the backlight all the way off at the lowest levels.
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Clamp saved brightness to at least 1 or 5% of max_brightness. This
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avoids preserving an unreadably dim screen, which would otherwise force
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the user to disable state restoration.
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---
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src/backlight/backlight.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
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1 file changed, 44 insertions(+)
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diff --git src/backlight/backlight.c src/backlight/backlight.c
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index 81470b3..abf8bcf 100644
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--- src/backlight/backlight.c
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+++ src/backlight/backlight.c
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@@ -192,6 +192,48 @@ static bool validate_device(struct udev *udev, struct udev_device *device) {
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return true;
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}
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+/* Some systems turn the backlight all the way off at the lowest levels.
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+ * clamp_brightness clamps the saved brightness to at least 1 or 5% of
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+ * max_brightness. This avoids preserving an unreadably dim screen, which
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+ * would otherwise force the user to disable state restoration. */
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+static void clamp_brightness(struct udev_device *device, char **value) {
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+ int r;
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+ const char *max_brightness_str;
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+ unsigned brightness, max_brightness, new_brightness;
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+
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+ max_brightness_str = udev_device_get_sysattr_value(device, "max_brightness");
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+ if (!max_brightness_str) {
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+ log_warning("Failed to read max_brightness attribute; not checking saved brightness");
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+ return;
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+ }
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+
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+ r = safe_atou(*value, &brightness);
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+ if (r < 0) {
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+ log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r));
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+ return;
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+ }
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+
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+ r = safe_atou(max_brightness_str, &max_brightness);
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+ if (r < 0) {
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+ log_warning("Failed to parse max_brightness \"%s\": %s", max_brightness_str, strerror(-r));
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+ return;
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+ }
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+
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+ new_brightness = MAX3(brightness, 1U, max_brightness/20);
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+ if (new_brightness != brightness) {
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+ char *old_value = *value;
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+
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+ r = asprintf(value, "%u", new_brightness);
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+ if (r < 0) {
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+ log_oom();
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+ return;
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+ }
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+
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+ log_debug("Saved brightness %s too low; increasing to %s.", old_value, *value);
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+ free(old_value);
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+ }
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+}
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+
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int main(int argc, char *argv[]) {
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_cleanup_udev_unref_ struct udev *udev = NULL;
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_cleanup_udev_device_unref_ struct udev_device *device = NULL;
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@@ -306,6 +348,8 @@ int main(int argc, char *argv[]) {
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return EXIT_FAILURE;
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}
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+ clamp_brightness(device, &value);
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+
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r = udev_device_set_sysattr_value(device, "brightness", value);
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if (r < 0) {
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log_error("Failed to write system attribute: %s", strerror(-r));
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--
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1.7.9.2
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