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 0DA0D2C2ABF; Sun, 1 Feb 2026 20:35:11 +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=1769978112; cv=none; b=kONZtMnpZL+2w0hM0hps3qXbkWa+7W6/GjTFwwtggZzg2ZA78IvfOB1/X3wVg5VmFPvXUYG/Enh/z5ZPSTGUYZWru0AhfTxt4h+TQ44JC+ywaFaQ4gkwAIKOJabk7uESwNjKLEwmsRc/T7CkZpKvl/UF8pdig/M0Scp14dOC5OI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769978112; c=relaxed/simple; bh=9AZrhuP8bJLjru6u0kp/mk9SAFQNQD2+eLv5yuCJgaY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cQ6tKBaGsBnD6P6NH9XesTLDPqDZxhPgVd83UtIkx6JoXfcPfIo2jn7b+jcgTZj8AJKv5Glq7RCcC/L3lZN6rcP9/BG+J0iwaF9Ndq8V5NBne8HixYI6bp19O/ptM4Oez42AC4TfflkZ7gK34TbrPct51x1XNByvk4c3h7p+Mto= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GZijpDo7; 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="GZijpDo7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE560C4CEF7; Sun, 1 Feb 2026 20:35:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769978111; bh=9AZrhuP8bJLjru6u0kp/mk9SAFQNQD2+eLv5yuCJgaY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GZijpDo7Mtt/eY5gpTObZFgO9Gge1VW53ncaleQp/tra7TkvgpidQzz+mDnjNZNOF lAgr2+GLep96rAwPleBHW9FzrLU98erxIY70EXbgB4fywpTStvyG0BqnzWnB75edFG lz4MqWcDsti8Rmm4ceiKxPhYA9BLHnucXCnz54Yvdd1kfRNAmApJQliVg1ndhop4Vn rQ/iB1YI7U3GBQ2PbQtIorevHHbY/Sd5UOjLwdhyKvrdjADlXdVmLEK5A1npfBHaix ajynoRV5c1ei5k+g02oOF1YxcNPDxveZopArXd290yh1X5j4tGoGTEzUKDzkvYgBKr pJ3eRdEDJvf0g== Date: Sun, 1 Feb 2026 22:35:06 +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> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260201200649.GW3374091@killaraus> 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. > > > 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 BR, Jarkko