Re: [PATCH] Platform: samsung-laptop: add DMI information for Samsung N150 Plus

From: "Richard Schütz" <r.schtz@t-online.de>
To: Corentin Chary <corentin.chary@gmail.com>
Cc: David Herrmann <dh.herrmann@googlemail.com>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Andrzej Prochyra <andrzej@prochyra.name>,
	platform-driver-x86@vger.kernel.org,
	linux-kernel@vger.kernel.org, "Zhang, Rui" <rui.zhang@intel.com>
Subject: Re: [PATCH] Platform: samsung-laptop: add DMI information for Samsung N150 Plus
Date: Thu, 29 Dec 2011 12:45:52 +0100	[thread overview]
Message-ID: <4EFC52F0.1010709@t-online.de> (raw)
In-Reply-To: <4EFC3FA8.6020401@gmail.com>

Am 29.12.2011 11:23, schrieb Corentin Chary:
> On 12/26/2011 11:22 AM, David Herrmann wrote:
>> On Mon, Dec 26, 2011 at 10:49 AM, Corentin Chary
>> <corentin.chary@gmail.com> wrote:
>>> On Sat, Dec 24, 2011 at 3:28 PM, David Herrmann
>>> <dh.herrmann@googlemail.com> wrote:
>>>> On Sat, Dec 24, 2011 at 3:20 PM, Matthew
>>>> Garrett<mjg59@srcf.ucam.org> wrote:
>>>>> On Sat, Dec 24, 2011 at 02:12:57PM +0000, Andrzej Prochyra wrote:
>>>>>> 'acpi_video0' not functional. Brightness can be controlled through
>>>>>> intel_backlight interface. There are 21 brightness levels and the
>>>>>> backlight can be turned off.
>>>>>
>>>>> If acpi_video0 doesn't work then we either need to work out why
>>>>> it's not
>>>>> working or make it vanish completely, so this patch isn't the correct
>>>>> approach.
>>>>
>>>> Just to make clear, intel_backlight isn't working properly either. If
>>>> my laptop boots with backlight at 50% then intel_backlight will only
>>>> work in the range 0%-50% on my machine. If I use the samsung module to
>>>> set it to 100% then intel_backlight works correctly in the range
>>>> 0-100% until next reboot/suspend.

The same problem exists on my N145 Plus, too.

>>>> So I'd recommend staying with the samsung module and disabling the
>>>> acpi_backlight entirely. The samsung module is the only backlight
>>>> control which works properly.
>>>
>>> Can I take a look at the DSDT to see how it's broken ?
>>> If it's really not functional, then it should be added to the
>>> blacklist in video_detect.c
>>
>> Raw and disassembled dsdt is attached.
>
> Took a quick look but didn't find anything obvious. What happens exactly
> with acpi_video0 ?

Either Samsung's ACPI is totally broken [ACPI Warning: _BQC returned an 
invalid level (20110623/video-472)] or they just don't support backlight 
setting via ACPI at all. Therefore it's implemented in the SABI stuff. 
So every device that needs SABI should be blacklisted in video_detect.

-- 
Regards,
Richard Schütz