linux-kernel - Re: [PATCH v2 1/3] drm: Add panel backlight quirks

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Message-ID: <93677810-55e5-40b9-8756-c10820dc890e@amd.com>
Date: Mon, 24 Jun 2024 13:37:47 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Hans de Goede <hdegoede@...hat.com>,
 Thomas Weißschuh <linux@...ssschuh.net>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>,
 Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
 Matt Hartley <matt.hartley@...il.com>, Kieran Levin <ktl@...mework.net>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Dustin Howett <dustin@...ett.net>,
 Matthew Anderson <ruinairas1992@...il.com>,
 "Derek J. Clark" <derkejohn.clark@...il.com>
Subject: Re: [PATCH v2 1/3] drm: Add panel backlight quirks

On 6/23/2024 15:55, Hans de Goede wrote:
> Hi,
> 
> On 6/23/24 10:20 PM, Mario Limonciello wrote:
>> On 6/23/2024 03:51, Thomas Weißschuh wrote:
>>> Panels using a PWM-controlled backlight source without an do not have a
>>> standard way to communicate their valid PWM ranges.
>>> On x86 the ranges are read from ACPI through driver-specific tables.
>>> The built-in ranges are not necessarily correct, or may grow stale if an
>>> older device can be retrofitted with newer panels.
>>>
>>> Add a quirk infrastructure with which the valid backlight ranges can be
>>> maintained as part of the kernel.
>>>
>>
>> So I was just talking to some folks in the Linux handheld gaming community (added to CC) about an issue they have where they need to know the correct panel orientation.  Due to reuse of panels across vendors the orientation on one might not be appropriate on another.  The trick is then to detect the combo of both the panel and the DMI data.
>>
>> It's the same "kind" of problem where something advertised in the firmware should be ignored but only on a panel + SMBIOS combination.
>>
>> So I am wondering if what you're proposing here could be more generalized.  IE "drm_panel_quirks.c" instead?
>>
>> Thoughts?
> 
> Note we already have a quirk mechanism for non upright mounted lcd-panels:
> 
> drivers/gpu/drm/drm_panel_orientation_quirks.c
> 
> note that the info here is shared with the simpledrm and
> efifb drivers, so if the chose is made to extend this then
> that needs to be taken into account.
> 
> Regards,
> 
> Hans

Thanks for sharing.  Totally agree this is this the better way to go for 
what I raised.