From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-by2nam01on0130.outbound.protection.outlook.com ([104.47.34.130]:4160 "EHLO NAM01-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933160AbeCSPrX (ORCPT ); Mon, 19 Mar 2018 11:47:23 -0400 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Hans de Goede , "Rafael J . Wysocki" , Sasha Levin Subject: [PATCH AUTOSEL for 4.15 018/124] ACPI / video: Default lcd_only to true on Win8-ready and newer machines Date: Mon, 19 Mar 2018 15:47:17 +0000 Message-ID: <20180319154645.11350-18-alexander.levin@microsoft.com> References: <20180319154645.11350-1-alexander.levin@microsoft.com> In-Reply-To: <20180319154645.11350-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org List-ID: From: Hans de Goede [ Upstream commit 5928c281524fe451114e04f1dfa11246a37e859f ] We're seeing a lot of bogus backlight interfaces on newer machines without a LCD such as desktops, servers and HDMI sticks. This causes userspace to show a non-functional brightness slider in e.g. the GNOME3 system menu, which is undesirable. And, in general, we should simply just not register a non functional backlight interface. Checking the LCD flag causes the bogus acpi_video backlight interfaces to go away (on the machines this was tested on). This change sets the lcd_only option by default on any machines which are Win8-ready, to fix this. This is not entirely without a risk of regressions, but video_detect.c already prefers native-backlight interfaces over the acpi_video one on Win8-ready machines, calling acpi_video_unregister_backlight() as soon as a native interface shows up. This is done because the ACPI backlight interface often is broken on Win8-ready machines, because win8 does not seem to actually use it. So in practice we already end up not registering the ACPI backlight interface on (most) Win8-ready machines with a LCD panel, thus this change does not change anything for (most) machines with a LCD panel and on machines without a LCD panel we actually don't want to register any backlight interfaces. This has been tested on the following machines and fixes a bogus backlight interface showing up there: - Desktop with an Asrock B150M Pro4S/D3 m.b. using i5-6500 builtin gfx - Intel Compute Stick STK1AW32SC - Meegopad T08 HDMI stick Bogus backlight interfaces have also been reported on: - Desktop with Asus H87I-Plus m.b. - Desktop with ASRock B75M-ITX m.b. - Desktop with Gigabyte Z87-D3HP m.b. - Dell PowerEdge T20 desktop Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D1097436 Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D1133327 Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D1133329 Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D1133646 Signed-off-by: Hans de Goede Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin --- drivers/acpi/acpi_video.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c index 0972ec0e2eb8..f53ccc680238 100644 --- a/drivers/acpi/acpi_video.c +++ b/drivers/acpi/acpi_video.c @@ -80,8 +80,8 @@ MODULE_PARM_DESC(report_key_events, static bool device_id_scheme =3D false; module_param(device_id_scheme, bool, 0444); =20 -static bool only_lcd =3D false; -module_param(only_lcd, bool, 0444); +static int only_lcd =3D -1; +module_param(only_lcd, int, 0444); =20 static int register_count; static DEFINE_MUTEX(register_count_mutex); @@ -2136,6 +2136,16 @@ int acpi_video_register(void) goto leave; } =20 + /* + * We're seeing a lot of bogus backlight interfaces on newer machines + * without a LCD such as desktops, servers and HDMI sticks. Checking + * the lcd flag fixes this, so enable this on any machines which are + * win8 ready (where we also prefer the native backlight driver, so + * normally the acpi_video code should not register there anyways). + */ + if (only_lcd =3D=3D -1) + only_lcd =3D acpi_osi_is_win8(); + dmi_check_system(video_dmi_table); =20 ret =3D acpi_bus_register_driver(&acpi_video_bus); --=20 2.14.1