From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Subject: Re: [REGRESSION] [v2] ACPI / video: Default lcd_only to true on Win8 ready and newer machines Date: Tue, 17 Apr 2018 17:20:37 +0200 Message-ID: References: <20171223184147.12016-1-hdegoede@redhat.com> <20180414230746.GA29537@saruman> <20180415225403.GA6373@jamesdev> <18c72a70-577f-358e-fb82-095b75157a29@redhat.com> <20180416130211.GA484@jamesdev> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180416130211.GA484@jamesdev> Content-Language: en-US Sender: stable-owner@vger.kernel.org To: James Hogan Cc: Zhang Rui , "Rafael J . Wysocki" , Len Brown , linux-acpi@vger.kernel.org, stable@vger.kernel.org, Sasha Levin , Greg Kroah-Hartman List-Id: linux-acpi@vger.kernel.org Hi James, On 04/16/2018 03:02 PM, James Hogan wrote: > On Mon, Apr 16, 2018 at 01:07:50PM +0200, Hans de Goede wrote: >> On 16-04-18 00:54, James Hogan wrote: >>> On Sun, Apr 15, 2018 at 02:04:26PM +0200, Hans de Goede wrote: >>>> When you say quirk do you mean you add something to >>>> the kernel commandline to work around this? >>> >>> No, it was automatic, in the source. I don't know this code well enough >>> to know how they got it working. >> >> Weird, if my only_lcd changes impact you then acpi_osi_is_win8() >> returns true for you > > It rings a bell that this laptop claims win8 support. > >> you should get the intel backlight interface >> by default, but maybe the i915 driver somehow detects that that >> is not appropriate on your device ... ? >> >> Before I can start working on a quirk to fix this I've some >> questions: >> >> 1) With recent kernels without the 965736ee654d commit, what is >> the output of "ls /sys/class/backlight" ? > > $ ls -l /sys/class/backlight > total 0 > lrwxrwxrwx 1 root root 0 Apr 16 13:57 acpi_video0 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video0 > >> 2) What is the output of "ls /sys/class/backlight" after >> commit 965736ee654d ? > > no devices show up there. > >> 3) Can you start a kernel with commit 965736ee654d in there and >> "video.only_lcd=0" on the kernel commandline and verify that >> this fixes backlight control for you ? > > Confirmed, acpi_video0 shows up and backlight control works as expected. Ok, so rather then DMI quirk our way out of this I've come up with a more generic solution. I've just send out a "[RFC] ACPI / video: Only default only_lcd to true on Win8-ready _desktops_" patch which should fix this. Can you give this patch a quick spin (on top of the troublesome commit) and let me know if it fixes things (without needing the kernel cmdline option). Regards, Hans