diff options
| -rw-r--r-- | src/backlight/backlight.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c index 81470b3f9d..abf8bcf00e 100644 --- a/src/backlight/backlight.c +++ b/src/backlight/backlight.c @@ -192,6 +192,48 @@ 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) { + int r; + const char *max_brightness_str; + unsigned brightness, max_brightness, new_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; + } + + r = safe_atou(*value, &brightness); + if (r < 0) { + log_warning("Failed to parse brightness \"%s\": %s", *value, strerror(-r)); + return; + } + + 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; + } + + 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; @@ -306,6 +348,8 @@ int main(int argc, char *argv[]) { return EXIT_FAILURE; } + clamp_brightness(device, &value); + r = udev_device_set_sysattr_value(device, "brightness", value); if (r < 0) { log_error("Failed to write system attribute: %s", strerror(-r)); |