From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Lu Subject: [PATCH 2/2] ACPI / video: Quirk initial backlight level 0 Date: Wed, 06 Nov 2013 09:07:10 +0800 Message-ID: <5279963E.8030109@intel.com> References: <52799553.7020406@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mga02.intel.com ([134.134.136.20]:39046 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755373Ab3KFBG0 (ORCPT ); Tue, 5 Nov 2013 20:06:26 -0500 In-Reply-To: <52799553.7020406@intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: ACPI Devel Mailing List , Qingshuai Tian , erno@iki.fi, Kirill Tkhai , Shuduo Sang Some firmware doesn't initialize initial backlight level to a proper value and _BQC will return 0 on first time evaluation. We used to be able to detect such incorrect value with our code logic, as value 0 normally isn't a valid value in _BCL. But with the introduction of Win8, firmware begins to fill _BCL with values from 0 to 100, now 0 becomes a valid value but that value will make user's screen black. This patch test initial _BQC for value 0, if such a value is returned, do not use it. Reference: https://bugzilla.kernel.org/show_bug.cgi?id=64031 Reference: https://bugzilla.kernel.org/show_bug.cgi?id=61231 Reference: https://bugzilla.kernel.org/show_bug.cgi?id=63111 Reported-by: Qingshuai Tian Tested-by: Aaron Lu on "Idealpad u330p" Reported-and-tested-by: on "Acer Aspire V5-573G" Reported-and-tested-by: Kirill Tkhai on "HP 250 G1" Signed-off-by: Aaron Lu Cc: stable --- drivers/acpi/video.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index bf521b36c2f9..a049fa9360d0 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -858,7 +858,7 @@ acpi_video_init_brightness(struct acpi_video_device *device) for (i = 2; i < br->count; i++) if (level == br->levels[i]) break; - if (i == br->count) + if (i == br->count || !level) level = max_level; } -- 1.8.4.39.ga0d3f10