linux-kernel - Re: [RFC PATCH v2] media: Virtual camera driver

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Message-ID: <2bda02cb3da6cb6ca7dcf545a5b7af27fb7a6e37@intel.com>
Date: Tue, 03 Feb 2026 20:53:13 +0200
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: johannes.goede@....qualcomm.com, Jarkko Sakkinen <jarkko@...nel.org>,
 linux-media@...r.kernel.org
Cc: anisse@...ier.eu, oleksandr@...alenko.name,
 linux-integrity@...r.kernel.org, Mauro Carvalho Chehab
 <mchehab@...nel.org>, Hans Verkuil <hverkuil@...nel.org>, Laurent Pinchart
 <laurent.pinchart@...asonboard.com>, Sakari Ailus
 <sakari.ailus@...ux.intel.com>, Jacopo Mondi
 <jacopo.mondi@...asonboard.com>, Ricardo Ribalda <ribalda@...omium.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2] media: Virtual camera driver

On Tue, 03 Feb 2026, johannes.goede@....qualcomm.com wrote:
> OTHO evdi: https://github.com/DisplayLink/evdi has been kept out
> of the kernel for pretty much the same reasons by the drm/kms folks.
>
> At least AFAIK there still is no way to present virtual kms capable
> display outputs backed by userspace in the kernel.
>
> I completely understand where you're coming from wrt v4l2-loopback
> support (or something equivalent) but asking for this really is
> the same as asking for the evdi driver to get merged, which AFAIK
> has been blocked for the reason of avoiding proprietary userspace
> display output drivers (I guess there might be technical reasons too).

I'm not sure this is the same thing, though.

The DRM subsystem does require an open source userspace for new uAPI,
which is stricter than most subsystems [1]. Other than that, I don't
think anyone's actively keeping evdi out of the kernel. AFAIK there
hasn't been a serious attempt at upstreaming it either. Which is pretty
much because there's no open userspace. Nobody's cared enough to either
write one or open source the existing one for a decade [2].


BR,
Jani.


[1] https://docs.kernel.org/gpu/drm-uapi.html#open-source-userspace-requirements
[2] https://github.com/DisplayLink/evdi/issues/25

-- 
Jani Nikula, Intel