From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932419Ab3K0A6g (ORCPT ); Tue, 26 Nov 2013 19:58:36 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:39295 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932406Ab3K0A63 (ORCPT ); Tue, 26 Nov 2013 19:58:29 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qingshuai Tian , Aaron Lu , "Rafael J. Wysocki" Subject: [PATCH 3.12 022/116] ACPI / video: Quirk initial backlight level 0 Date: Tue, 26 Nov 2013 16:56:35 -0800 Message-Id: <20131127005738.480750511@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.rc3 In-Reply-To: <20131127005736.915454872@linuxfoundation.org> References: <20131127005736.915454872@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aaron Lu commit 2c62333a408f5badd2d2ffd7177f95deeccc5ca4 upstream. 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. References: https://bugzilla.kernel.org/show_bug.cgi?id=64031 References: https://bugzilla.kernel.org/show_bug.cgi?id=61231 References: 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 Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/acpi/video.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -832,7 +832,7 @@ acpi_video_init_brightness(struct acpi_v for (i = 2; i < br->count; i++) if (level_old == br->levels[i]) break; - if (i == br->count) + if (i == br->count || !level) level = max_level; }