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 006F928314B; Sun, 1 Feb 2026 21:01:47 +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=1769979709; cv=none; b=DHPC54/iupXTb2aXAAOz6cyWEDAsWHcj5TXOyFKatBTaAIzLm2V5ej4vXRXgQY00hj2DFvVEjpK+Cpg5XYEP/PZ3Qm1iHMh/35N9UOIIaEfuGLLLPHsJ1XFD71wITk33yYrBjW4prqCpXdTwnBNbdcIPIF6zRTWpMLudM+wPZqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769979709; c=relaxed/simple; bh=vjhiCNXVEl4JwTm9FOMfP9G8iIONK7YsIk6rcyN+OQQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LasZECmhaVx6ikm4zpUfpbNCljgB4LABYRhWoBTyqnDI7Dn6ARSZ152hs7oL60M77iCmK1xQqK8BmoWtIQDIrT2DFXLBReANrbvIyoLayc10Inb+mceR+rSfFFUn2GaazseVkqu8Hqv1Pt6xEJhzoWj/yT71rSEmZLZIRnA5rwU= 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=HhFat/aj; 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="HhFat/aj" 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 AE9244E1; Sun, 1 Feb 2026 22:01:05 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1769979665; bh=vjhiCNXVEl4JwTm9FOMfP9G8iIONK7YsIk6rcyN+OQQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HhFat/ajvZxz+CrymkcVyhI0lTtklLAo5Zbge4n4Tquh5Pycb+vSglK0rPJLTtSou kvm+Rpzp954bGsYGYcVmywLr4+FXbPTgle82J9J9te4MKKOgZvPzqWupYCOHOV+ZPG UIfVj0XBe7sueWDejBiToEWgsTmbPzCvPTXtxV/o= Date: Sun, 1 Feb 2026 23:01:44 +0200 From: Laurent Pinchart To: Jarkko Sakkinen Cc: linux-media@vger.kernel.org, jani.nikula@linux.intel.com, anisse@astier.eu, oleksandr@natalenko.name, Mauro Carvalho Chehab , Hans Verkuil , Sakari Ailus , Jacopo Mondi , Ricardo Ribalda , open list Subject: Re: [RFC PATCH] media: Virtual camera driver Message-ID: <20260201210144.GZ3374091@killaraus> References: <20260201133342.335680-1-jarkko@kernel.org> <20260201182011.GV3374091@killaraus> <20260201200649.GW3374091@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 Sun, Feb 01, 2026 at 10:35:06PM +0200, Jarkko Sakkinen wrote: > On Sun, Feb 01, 2026 at 10:06:49PM +0200, Laurent Pinchart wrote: > > On Sun, Feb 01, 2026 at 09:04:00PM +0200, Jarkko Sakkinen wrote: > > > On Sun, Feb 01, 2026 at 08:20:11PM +0200, Laurent Pinchart wrote: > > > > On Sun, Feb 01, 2026 at 03:33:38PM +0200, Jarkko Sakkinen wrote: > > > > > vcam is a DMA-BUF backed virtual camera driver capable of creating video > > > > > capture devices to which data can be streamed through /dev/vcam after > > > > > calling VCAM_IOC_CREATE. Frames are pushed with VCAM_IOC_QUEUE and recycled > > > > > with VCAM_IOC_DEQUEUE. > > > > > > > > > > Zero-copy semantics are supported for shared DMA-BUF between capture and > > > > > output. > > > > > > > > > > Signed-off-by: Jarkko Sakkinen > > > > > --- > > > > > Early feedback e.g., is this completely in wrong direction? V4L2 world > > > > > is relatively alien world, and thus I need a sanity check ;-) > > > > > > > > We already have multiple virtual drivers, including vivid and vimc. > > > > Could you please explain the rationale for yet another one, and why the > > > > new features it provides (if any) can't be added to existing drivers ? > > > > > > There is a notable user base for v4l2-loopback. It is the defacto choice > > > for streaming phone cams. > > > > This will then likely face the same hurdles as v4l2-loopback, the main > > one being that camera support should be upstreamed with proper drivers > > instead of a closed-source userspace daemon. > > > > For phone cameras, the way forward upstream is libcamera. Until kernel > > drivers for ISPs are available, the soft ISP is a stop-gap solution. It > > recently gained GPU acceleration support (with work to improve image > > quality with additional algorithms ongoing). > > That might have some weight as a pro but the unarguable con is that at > the same time this policy retains a base of tainted kernels in the wild. Do you mean tainted by the out-of-tree v4l2loopback module ? Won't those systems be equally tainted by out-of-tree camera drivers then ? With libcamera and the soft ISP you can run a 100% mainline stack. > Not saying that this weight more but it is important to remark this > fact. > > > > The motivation here is to provide a service optimized for that use and > > > purpose. It's virtual but non-generic i.e. not aimed for testing/emulation. > > > > > > > > .../driver-api/media/drivers/index.rst | 1 + > > > > > .../driver-api/media/drivers/vcam.rst | 16 + > > > > > MAINTAINERS | 8 + > > > > > drivers/media/Kconfig | 13 + > > > > > drivers/media/Makefile | 1 + > > > > > drivers/media/vcam.c | 1700 +++++++++++++++++ > > > > > include/uapi/linux/vcam.h | 124 ++ > > > > > 7 files changed, 1863 insertions(+) > > > > > create mode 100644 Documentation/driver-api/media/drivers/vcam.rst > > > > > create mode 100644 drivers/media/vcam.c > > > > > create mode 100644 include/uapi/linux/vcam.h > > > > [snip] -- Regards, Laurent Pinchart