From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 340CE347DD; Mon, 2 Feb 2026 01:44:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769996672; cv=none; b=Gl7p9xaRUA5bAXPPPffbV7XVSFrIJjGG2anOppDRZa7tMkyyIwVt8/KO2N0Woh3G8tjMEfZz+lx8RlMH5QPWpchlxZVJQ29gmtiKK595eRCmDpNRmgtoBUGgbX06tNPYyNqTwbiADWuNuoKeEvT3YoASew7xobknhzqExcRK/mg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769996672; c=relaxed/simple; bh=fuhwN3cisTYdLDz37vq+hN2egM0+uS30hgOu5Kl3oCM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MMOPep/woIQe8q/mlLsPGTp1HNWryItIx5kYPJiDxPQhjcQ72c7iDDIZd3JSf0JOWptJ7rMgaqWekIzFhC7mneVuCa54wa1RK7KWkc95BfobRSLghNwCh6dOfPFNtoTxNke/X2umYxgbWu8MHrYi70B6kWwYtBi6iAilgyQ9U6U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=urHmwzCV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="urHmwzCV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44A55C4CEF7; Mon, 2 Feb 2026 01:44:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769996671; bh=fuhwN3cisTYdLDz37vq+hN2egM0+uS30hgOu5Kl3oCM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=urHmwzCVgkFbOZo7OGKugEkgBr3D5UWx8f76xM7KWkRZEcHUpiimse8UzbFdxw3ZN WUgg8C45ypBOY+aSbkpS8LRCsrCrrZ5JaqcGqUq8UdH/J3C/GScgojXOK+1ijdaKQ3 0mu6f4CGBus9RMGcFpEkVm/ecdGIIB4fJ1f4Au2V6boBDQKpW7rzIZtL/Fvijrhwuh qMSkq9VfrV/ITsLI4lfnnQUGxvgWAt9tZDw0Ak/VlwQjbnR5Mv1dQrMqGbd6kOH3Y4 ALbwG6QtFARDRQx3zKHC7EV+3xPUjYmq9SEa0ULiaQoX75PwCJhrRLZPHr9lq93tEA MoiyzNCJWKUmg== Date: Mon, 2 Feb 2026 03:44:27 +0200 From: Jarkko Sakkinen To: Laurent Pinchart 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: References: <20260201133342.335680-1-jarkko@kernel.org> <20260201182011.GV3374091@killaraus> <20260201200649.GW3374091@killaraus> <20260201210952.GA3374091@killaraus> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260201210952.GA3374091@killaraus> On Sun, Feb 01, 2026 at 11:09:52PM +0200, Laurent Pinchart wrote: > On Sun, Feb 01, 2026 at 10:54:34PM +0200, Jarkko Sakkinen wrote: > > On Sun, Feb 01, 2026 at 10:35:12PM +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. > > > > > > Not saying that this weight more but it is important to remark this > > > fact. > > > > It's widely packaged for different distributions and even embedded build > > systems forming across the board tained ecosystem. And this has been > > ongoing for years. Suggesting PipeWire as "a fix" for all possible > > situations is not "a solution". > > PipeWire may not solve all of the world's problems, but it's part of a > clean solution for this particular issue. The fact that everybody relied > on an out-of-tree kernel module instead of designing a better stack is > not a reason to merge v4l2loopback upstream now that we have a better > option that is actively developed. Nobody (at least not in this thread) requested to merge v4l2-loopback upstream. Let's use correct terminology in order not convolute the discussion further, thank you. > > -- > Regards, > > Laurent Pinchart BR, Jarkko