From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A6E872DF6F6; Tue, 3 Feb 2026 21:21:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770153675; cv=none; b=iljtzB+M8tctIE8PTfcBrMJ5OvEGnItDr6K7esKclNov9c6RBrC98eSXyyXKnoRRPA8trK1t0B5IITjPCoHSmC/mjCP9Mu9GttEVfinxX8p/sbb2NdHAbe/+nkO2nvVMWv1r/tfKq6jBwvfOzzLwtC++iHGDzCCMIAyfWOeCSkg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770153675; c=relaxed/simple; bh=z1EHnPmuKMdWMT+IPlFg3F7DzJ5bhjGiWyCV84R0Hwk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HH0cb/m9QZoU41o0T11ru8c4NTbXUDJcqtwfK7VrSuQRJMfhXsxbq0a99A7D3Xr01EPkTT46mfdchI1UZMCZAj8YkF4KxEbp8shKWUnrySjCqBWDR8bm6ZsPSVqITyoak9IVN2IGGgLf8Cdjb+jITtYpkr/WCZcX0Afl6DFpr9I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=Et3PqK/c; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="Et3PqK/c" Received: from killaraus.ideasonboard.com (2001-14ba-703d-e500--2a1.rev.dnainternet.fi [IPv6:2001:14ba:703d:e500::2a1]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 51BA3673; Tue, 3 Feb 2026 22:20:30 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1770153630; bh=z1EHnPmuKMdWMT+IPlFg3F7DzJ5bhjGiWyCV84R0Hwk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Et3PqK/ceUJ1+RKqUNnGDUCEaJeUf6g8pOkMly3n0iixQbSZaeeVcfvnw2ewqqDYp ADcajVscGanWac7nh9xzolesvypOfkwdkv1rjaSRc0KiapoXMNHOK6z6znAlYmlC7d UPWFAI/lxkrk/ek2o0uHtK4FG9LLIVa7fjin+Uis= Date: Tue, 3 Feb 2026 23:21:10 +0200 From: Laurent Pinchart To: Jarkko Sakkinen Cc: Sakari Ailus , linux-media@vger.kernel.org, jani.nikula@linux.intel.com, anisse@astier.eu, oleksandr@natalenko.name, linux-integrity@vger.kernel.org, Mauro Carvalho Chehab , Hans Verkuil , Jacopo Mondi , Ricardo Ribalda , open list Subject: Re: [RFC PATCH v2] media: Virtual camera driver Message-ID: <20260203212110.GE11369@killaraus> References: <20260202204425.2614054-1-jarkko@kernel.org> <20260203205742.GB11369@killaraus> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Tue, Feb 03, 2026 at 11:11:19PM +0200, Jarkko Sakkinen wrote: > On Tue, Feb 03, 2026 at 10:57:42PM +0200, Laurent Pinchart wrote: > > On Tue, Feb 03, 2026 at 03:36:59AM +0200, Jarkko Sakkinen wrote: > > > On Tue, Feb 03, 2026 at 02:10:15AM +0200, Jarkko Sakkinen wrote: > > > > On Tue, Feb 03, 2026 at 12:50:06AM +0200, Sakari Ailus wrote: > > > > > On Mon, Feb 02, 2026 at 10:44:21PM +0200, Jarkko Sakkinen wrote: > > > > > > Already a quick Google survey backs strongly that OOT drivers (e.g., > > > > > > v4l2loopback) are the defacto solution for streaming phone cameras in > > > > > > video conference calls, which puts confidential discussions at risk. > > > > > > > > > > As I think it was pointed out in review comments for v1, the reason behind > > > > > using v4l2loopback is the use of a downstream driver, which itself is a > > > > > source of a security risk. If I understand correctly, supporting this > > > > > (proprietary/downstream vendor drivers) would be the main use case this > > > > > driver serves? Should this downstream driver be upstreamed to alleviate the > > > > > security risks, the need for v4l2loopback or similar drivers presumably > > > > > disappears. > > > > > > > > My goal is not to proactively support proprietary drivers, and I don't > > > > know how to measure such incentive or risk, when it comes to video > > > > drivers. > > > > > > > > And besides there is e.g. FUSE. > > > > > > > > > Another of the downsides of such proprietary/downstream solutions is they > > > > > can never be properly integrated into the Linux ecosystem so functionality > > > > > will remain spotty (limited to specific systems and specific releases of > > > > > specific distributions) at best. > > > > > > > > > > In other words, this driver appears to be orthogonal to solving either of > > > > > the above two problems the proprietary/downstream solutions have. > > > > > > > > > > From the Open Source libcamera based camera software stack point of view > > > > > there doesn't seem to be a need for v4l2loopback or another similar driver. > > > > > The two main reasons for this is that (1) there's no need for glueing > > > > > something separate together like this and (2) V4L2 isn't a great > > > > > application interface for cameras -- use libcamera or Pipewire instead. > > > > > > > > While I get this argument isolated, it does not match the observed > > > > reality, and does not provide tools to address the core issue. I > > > > will be in my grave before I've fixed the world like you are > > > > suggesting :-) > > > > I really hope we'll provide a solution much faster than that :-) > > > > > > Like, first off, where would I use libcamera or Pipewire? There's > > > > no well-defined target other than kernel in this problem. > > > > PipeWire is becoming the de facto media server on desktop systems, for > > both audio and video. It has been shipped by distributions for a while > > for audio, and is the core component that allows screen capture (and > > therefore screen sharing in video conferencing) on Wayland-based > > systems. For video, PipeWire support has most notably been integrated in > > WebRTC, used by both Firefox and Chrome. The number of applications > > using PipeWire is growing, OBS has recently received support for > > PipeWire sources for instance. If you need to use it in an application > > that requires a V4L2 capture device, the pw-v4l2 script emulates the > > V4L2 API to provide a quick stopgap measure until applications get > > native PipeWire support. > > > > libcamera solves an orthogonal problem, which is control of raw camera > > sensors and ISPs typically found in mobile and embedded devices, and now > > increasingly in laptops as well (Intel IPU3, IPU4, IPU6 and IPU7). > > Applications typically don't use libcamera directly, but interface it > > with GStreamer (libcamerasrc element) or PipeWire (which has native > > libcamera support). > > > > While I understand that libcamera and PipeWire may be quite new for a > > large number of users, the ecosystem is moving in that direction, and > > both projects are very active. > > Thanks for the information and I take this into account when/if considering > any updates. The response is so informative that I need to purge this a > bit (thank you for that) :-) This does not disregard your response but > personally I'm not have huge a fan of LD_PRELOAD style compatibility > wrappers. I'm not either as it can only provide best-effort compatibility, but it has proven to be useful. For instance, we successfully tested the libcamera LD_PRELOAD v4l2-compat.so with Firefox before support for PipeWire was ready in WebRTC, providing a way to use ISPs in video conferencing as a stopgap measure. It's all about helping the ecosystem with the transition, and not intended as a long-term solution. -- Regards, Laurent Pinchart