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 BC46F280CC9; Tue, 3 Feb 2026 21:18:21 +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=1770153503; cv=none; b=P+zCHizV5xjO9/flTHpEanBjcWC2LpvtWIW2WHmWpXtprPYkRE8Z0t4ss7StHvQ4hF9dICDR/R7FtK8u1KBtB3URL8nYtp5kZD3r87mZC4n2bHQALnhivXMts9Xddv/wJLSRrgP1vPt0gT7bIb+n80U+Zo35B2YPIJZGgwIADZs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770153503; c=relaxed/simple; bh=wKQ/vCSI4Fs56NbgbfPSvJ7FqZ6PZSVVyAUx3n2PNKQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=U8V2GfBO0eAP4in1t3pLwtuSd6c+v9X+KQxOCax737pkV22asR+2R7qtME9FHuQxNQXHoN6T2vHqEgZdHZdzhJlyFS3bOTjt/xTsk1R0gGqgkb9bMTH4m9LpwdxJTSymA9r236lZwg/oNe/RKUhMbXnYAWCII+cUGx43SLJUvUo= 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=R8cnpdEp; 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="R8cnpdEp" 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 5485B673; Tue, 3 Feb 2026 22:17:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1770153458; bh=wKQ/vCSI4Fs56NbgbfPSvJ7FqZ6PZSVVyAUx3n2PNKQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=R8cnpdEpedhk7rrBVZPF47OVSJrftKrUCeMmvjWHpmDaAmPm39uOmnon1wm6xiP/0 anwJvFFov3svYt+JC4XNJuSGab+mOdrrE42ALC1p7cQvS7Mk3Rw3ffPjcGI1hE6cXv Ngz3j8ySR7SqN8NNJ33qS7PX34ougN3oOLT7R3qs= Date: Tue, 3 Feb 2026 23:18:18 +0200 From: Laurent Pinchart To: johannes.goede@oss.qualcomm.com Cc: Jani Nikula , Jarkko Sakkinen , linux-media@vger.kernel.org, anisse@astier.eu, oleksandr@natalenko.name, linux-integrity@vger.kernel.org, Mauro Carvalho Chehab , Hans Verkuil , Sakari Ailus , Jacopo Mondi , Ricardo Ribalda , open list Subject: Re: [RFC PATCH v2] media: Virtual camera driver Message-ID: <20260203211818.GD11369@killaraus> References: <20260202204425.2614054-1-jarkko@kernel.org> <6b192c71-c389-4a6e-b7c3-ddcd5cc4aa34@oss.qualcomm.com> <37a0d91c2e78c97f3d956444c4f7a2a2fca9ae06@intel.com> 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 03:19:13PM +0100, johannes.goede@oss.qualcomm.com wrote: > On 3-Feb-26 14:20, Jani Nikula wrote: > > On Tue, 03 Feb 2026, johannes.goede@oss.qualcomm.com wrote: > >> The problem is that what you're suggesting is basically a much > >> improved (using dma-buf is way better) v4l2-loopback driver and > >> v4l2-loopback has been blocked from getting merged into the kernel > >> because besides the mobile-phone camera use, the other main use-case > >> is to allow running proprietary camera stacks like Intel's proprietary > >> camerastack and then presenting that to userspace as a standard v4l2 > >> cam so that userspace apps will just work. > > > > ... > > > >> The community concensus is that the solution here is for apps to > >> access cameras through pipewire. Together with the shift of laptops > >> cameras from UVC to "raw" MIPI cameras there also is a shift to > >> running applications sandboxed as flatpacks because of the changing > >> "cyber" security landscape. This is why pipewire was chosen because > >> it also solves the accessing cameras from a sandbox issue. > > > > Why is v4l2-loopback problematic from the perspective of facilitating > > running proprietary camera stacks, but pipewire isn't? > > Once pipewire mostly works everywhere for camera access then indeed > this will allow proprietary stacks to present themselves as a pipewire src. > For now though most proprietary stacks seem to prefer v4l2loopback because > pipewire is not supported as camera source yet by a lot of apps. I agree, that's a perfectly valid assessment of the situation. > As I indicated in my original email personally I'm a bit divided on > whether a virtual camera driver should be kept out of the kernel > to not promote proprietary userspace stacks, but this is not my call. Even disregarding that argument, the camera ecosystem is moving towards implementing those use cases entirely in userspace with PipeWire. I believe that merging a new kernel driver for this purpose, especially one that exposes a custom API on its sink side and would therefore require developing support in all source applications, goes against the direction we're taking overall. > 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). -- Regards, Laurent Pinchart