linux-kernel - Re: [PATCH v2] drm/client: Detect when ACPI lid is closed during initialization

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Date: Wed, 29 May 2024 23:41:12 -0500
From: "Limonciello, Mario" <mario.limonciello@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 linux-kernel@...r.kernel.org, Chris Bainbridge <chris.bainbridge@...il.com>,
 hughsient@...il.com
Subject: Re: [PATCH v2] drm/client: Detect when ACPI lid is closed during
 initialization

>> Also a direct acpi_lid_open() call seems a bit iffy. But I guess if
>> someone needs this to work on non-ACPI system they get to figure out
>> how to abstract it better. acpi_lid_open() does seem to return != 0
>> when ACPI is not supported, so at least it would err on the side
>> of enabling everything.
> 
> Thanks. I was going to comment, but you got it first. I think a proper
> implementation should check for SW_LID input device instead of simply
> using acpi_lid_open(). This will handle the issue for other,
> non-ACPI-based laptops.
> 

Can you suggest how this would actually work?  AFAICT the only way to 
discover if input devices support SW_LID would be to iterate all the 
input devices in the kernel and look for whether ->swbit has SW_LID set.

This then turns into a dependency problem of whether any myriad of 
drivers have started to report SW_LID.  It's also a state machine 
problem because other drivers can be unloaded at will.

And then what do you if more than one sets SW_LID?

IOW - a lot of complexity for a non-ACPI system.  Does such a problem 
exist in non-ACPI systems?