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

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Date: Thu, 30 May 2024 11:07:53 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: "Limonciello, Mario" <mario.limonciello@....com>, Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>, 
	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, linux-input@...r.kernel.org
Subject: Re: [PATCH v2] drm/client: Detect when ACPI lid is closed during initialization

On Thu, 30 May 2024 at 07:41, Limonciello, Mario
<mario.limonciello@....com> wrote:
>
>
> >> 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?

It might be easier to handle this in the input subsystem. For example
by using a refcount-like variable which handles all the LIDs and
counts if all of them are closed. Or if any of the LIDs is closed.

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

There are non-ACPI laptops. For example Chromebooks. Or Lenovo X13s,
Lenovo Yoga C630, Lenovo Flex5G, etc. We are expecting more to come in
the next few months. And I don't see why they won't have the same
problem.


-- 
With best wishes
Dmitry