linux-kernel - [PATCH AUTOSEL for 4.9 106/293] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

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Date:   Mon, 9 Apr 2018 00:24:16 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Kai Heng Feng <kai.heng.feng@...onical.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 106/293] platform/x86: dell-laptop: Fix bogus
 keyboard backlight sysfs interface

From: Kai Heng Feng <kai.heng.feng@...onical.com>

[ Upstream commit 1b1ffc57a1b2edf58e803e463980b326765a237f ]

Dell Latitude 3160 does not have keyboard backlight, but there is a
sysfs interface for it, which does nothing at all.

KBD_LED_ON_TOKEN is the only token can be found. Since it doesn't have
KBD_LED_OFF_TOKEN or KBD_LED_AUTO_*_TOKEN, it should be safe to assume
at least two tokens should be present to support keyboard backlight.
Not all models have ON token - they may have multiple AUTO tokens instead.

Models which do not use SMBIOS token to control keyboard backlight, also
have this issue. Brightness level is 0 on these models. Verified on Dell
Inspiron 3565.

Reports keyboard backlight is supported only when at least two modes are
present.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
Reviewed-by: Pali Rohár <pali.rohar@...il.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/platform/x86/dell-laptop.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
index 167d5042a629..175235fa75bc 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -1486,7 +1486,11 @@ static void kbd_init(void)
 	ret = kbd_init_info();
 	kbd_init_tokens();
 
-	if (kbd_token_bits != 0 || ret == 0)
+	/*
+	 * Only supports keyboard backlight when it has at least two modes.
+	 */
+	if ((ret == 0 && (kbd_info.levels != 0 || kbd_mode_levels_count >= 2))
+	    || kbd_get_valid_token_counts() >= 2)
 		kbd_led_present = true;
 }
 
-- 
2.15.1