linux-kernel - Re: [PATCH 4/4] media: uvcvideo: Introduce allow_privacy

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Message-ID: <CANiDSCuv8UG6TMx6pK348okK+NYzAorPEgPYzoRCEZiBDgPP=A@mail.gmail.com>
Date: Tue, 18 Nov 2025 19:28:22 +0100
From: Ricardo Ribalda <ribalda@...omium.org>
To: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, Hans de Goede <hansg@...nel.org>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 4/4] media: uvcvideo: Introduce allow_privacy_override

Hi Mauro

On Tue, 18 Nov 2025 at 15:09, Mauro Carvalho Chehab
<mchehab+huawei@...nel.org> wrote:
>
> On Tue, Nov 18, 2025 at 06:14:09AM -0500, Greg Kroah-Hartman wrote:
> > On Mon, Nov 17, 2025 at 08:14:19PM +0000, Ricardo Ribalda wrote:
> > > Some camera modules have XU controls that can configure the behaviour of
> > > the privacy LED.
> > >
> > > Block mapping of those controls, unless the module is configured with
> > > a new parameter: allow_privacy_override.
> >
> > This is not the 1990's, please do not add new module parameters, they do
> > not scale, nor work properly at all for modern hardware where you can
> > have multiple devices in the same system.
> >
> > This isn't an agreement that we should do this feature at all, just that
> > if you do, it should NOT be a module parameter.
>
> I agree with Greg: modprobe makes things harder, especially on usb.

If the argument is that with parameters you cannot have a different
parameter for each USB camera, I would say that I see this option as a
system-wide policy, not as a per-device option. But yeah, the less
parameters that we have, the better.

>
> Also, in the specific case of privacy leds, IMO it should never be
> possible to directly disable it, not even root via a modprobe or
> runtime parameter.

+1

>
> Ok, as it might be some case where someone really wants to disable for his
> special pet toy. If such cases are relevant, a Kconfig parameter could
> be added (maybe depending on BROKEN), having privacy LED enabled by default.
>
> This way, any sane distro-generated Kernel should always have the privacy
> LED on when camera is in use.
>
> On other words, if someone has secure boot enabled, he can be more confident
> that a distro-vendor signed Kernel will honour the privacy LED, and not
> even the root can tamper with - as BIOS access to disable secure boot would
> be needed to change it - plus, booting a non-signed kernel.

If most of the people agree that the final goal is to block all the
LED privacy access from userspace we could have a mixed approach.

1. We introduce the allow_privacy_override parameter with default off.
If the user sets allow_privacy_override, they are welcomed with a message like:

uvcvideo: [DEPRECATION]: Access to the privacy controls will be
eventually blocked.

2. In one year, if nobody screams at us we remove the parameter and
call it a day.

3. If someone depends on this feature, we will move it into a kernel
configuration behind BROKEN.

What do you think?

>
> Regards,
> Mauro



-- 
Ricardo Ribalda