linux-kernel - [PATCH v2 05/11] platform/x86: fujitsu-laptop: sync brightness in set_lcd

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Message-Id: <20170405064910.3162-6-kernel@kempniu.pl>
Date:   Wed,  5 Apr 2017 08:49:04 +0200
From:   Michał Kępień <kernel@...pniu.pl>
To:     Jonathan Woithe <jwoithe@...t42.net>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 05/11] platform/x86: fujitsu-laptop: sync brightness in set_lcd_level()

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@...pniu.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 6d4a2a36716b..b019060d6dc4 100644
--- a/drivers/platform/x86/fujitsu-laptop.c
+++ b/drivers/platform/x86/fujitsu-laptop.c
@@ -384,6 +384,8 @@ static int set_lcd_level(int level)
 		return -ENODEV;
 	}

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

-- 
2.12.2