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

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Message-ID: <aYJJWPLr4Qxkmn7z@kernel.org>
Date: Tue, 3 Feb 2026 21:15:36 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Jani Nikula <jani.nikula@...ux.intel.com>
Cc: johannes.goede@....qualcomm.com, linux-media@...r.kernel.org,
	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, Feb 03, 2026 at 09:07:41PM +0200, Jarkko Sakkinen wrote:
> On Tue, Feb 03, 2026 at 08:53:13PM +0200, Jani Nikula wrote:
> > 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].
> 
> This is unrelated of ACK/NACK and not saying this as a "selling point"
> but realistically speaking based on what I've read I have extremely hard
> time to believe that my driver would enable a market of proprietary
> camera drivers :-) Actually, after looking up mipi.org based on Hans
> response, I even more so believe that this is the case.

With my maintainer hat on, I'd get the nack better if the driver was
intrusive on changes to V4L2 subsystem itself. Then, it accumlates
weight to other maintainers, and as we all have limited amount of time
in our lives, I do get that. But since the driver would be compliance
aligning leaf driver with a MAINTAINER entry of its own, it should not
be a huge burden for V4L2 community and kernel maintainers.  And I do
have a track record of being long-term on maintaining stuff that I vomit
out.

That also does make difference as there are some guarantees that the
end product would not be left into rotten.

> 
> > BR,
> > Jani.
> 
> BR, Jarkko


BR, Jarkko