[PATCH 05/11] platform/x86: fujitsu-laptop: sync brightness in set_lcd_level()

Michał Kępień
2017-03-30T10:36:59Z

When using brightness keys and backlight device's sysfs interface
alternately, an incorrect input event might be generated for a
brightness key press. Consider the following sequence of events:

1. Set backlight brightness to 6 using brightness keys.
2. Write 4 to /sys/class/backlight/fujitsu-laptop/brightness.
3. Press the "brightness up" key.

The input event generated in this scenario would be KEY_BRIGHTNESSDOWN,
because before step 3 brightness_level would still be at 6. As the new
brightness level is established using GBLL, it would evaluate to 5
(SBLL/SBL2 sets it to 4 in step 2 and pressing the "brightness up" key
increases it by 1). This in turn would cause acpi_fujitsu_bl_notify()
to observe a 6 -> 5 change, i.e. a decrease in brightness, while screen
brightness would in fact be increased.

Fix this by updating brightness_level in set_lcd_level.

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
---
drivers/platform/x86/fujitsu-laptop.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
index b888ba190fb2..9981988f82d2 100644
--- a/drivers/platform/x86/fujitsu-laptop.c
+++ b/drivers/platform/x86/fujitsu-laptop.c
@@ -383,6 +383,8 @@ static int set_lcd_level(int level)
return -ENODEV;
}

+ fujitsu_bl->brightness_level = level;
+
return 0;
}

--
2.12.1