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Date: Fri, 8 Mar 2024 17:15:48 +0100
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Subject: Re: [PATCH v5] platform/x86: add lenovo wmi camera button driver
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To: =?UTF-8?B?6Im+6LaF?= <aichao@kylinos.cn>, hdegoede <hdegoede@redhat.com>,
 "ilpo.jarvinen" <ilpo.jarvinen@linux.intel.com>,
 linux-kernel <linux-kernel@vger.kernel.org>,
 platform-driver-x86 <platform-driver-x86@vger.kernel.org>
References: <1vk29ojvhrf-1vk4tk6plf0@nsmail7.0.0--kylin--1>
From: Armin Wolf <W_Armin@gmx.de>
Cc: dmitry.torokhov@gmail.com, linux-input@vger.kernel.org
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Am 08.03.24 um 09:40 schrieb =E8=89=BE=E8=B6=85:

> Hi
>
> =C2=A0=C2=A0=C2=A0 thanks for your help.
>
> > Is there a way to determine the current state of the camera switch
> without having
> > to wait for an WMI event?
>
> There is no other way to detemine the current state of the camera
> switch without
>
> a WMI event.
>
>
> > If its not possible to determine the current state of the camera
> switch, then your
> > driver has to defer the initialization of the input device until it
> knows the current
> > state of the camera switch. Otherwise the initial switch state
> reported by the
> > input device might be wrong.
>
> > In this case, that means your driver must initialize the input
> device when receiving
> > a valid WMI event for the first time.
>
> > Basically when your driver receives a WMI event, it has to check if
> the input device
> > is already initialized. If this is not the case, then the input
> device is initialized.
> > Please protect this check and the input device initialization with a
> mutex, since WMI
> > event handling is multithreaded.
>
>
> This Camera is a UVC device, and the Carema device is already
> initialized before the WMI
>
> event .=C2=A0 Whether the camera switch is on or off, we can used lsusb =
to
> check the Camera.
>
> This wmi-camera driver only need to report the current state of the
> camera switch.
>
>
> Thanks.
>
> =C2=A0=C2=A0=C2=A0 Ai Chao
>
I see, so userspace will notice when the camera is disabled. Since the cam=
era disappears from
the USB bus when the switch is activated, i wonder if SW_CAMERA_LENS_COVER=
 is the right thing
to use in this case after all.

I CCed the maintainer of the input subsystem so that he can maybe provide =
some advise.
I for example would, taking the above information above the UVC device int=
o account, say that
KEY_CAMERA_ACCESS_ENABLE/KEY_CAMERA_ACCESS_DISABLE is more suitable. Then =
userspace has to
keep track of the camera state (through lsusb for example).

Maybe someone knowing the input subsystem can provide some advise on what =
to do in this case?

Thanks,
Armin Wolf