Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751309AbdH1N2D (ORCPT ); Mon, 28 Aug 2017 09:28:03 -0400 Received: from ec2-52-27-115-49.us-west-2.compute.amazonaws.com ([52.27.115.49]:58361 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751152AbdH1N2B (ORCPT ); Mon, 28 Aug 2017 09:28:01 -0400 Date: Mon, 28 Aug 2017 10:27:51 -0300 From: Mauro Carvalho Chehab To: Hans Verkuil Cc: Linux Doc Mailing List , Linux Media Mailing List , Mauro Carvalho Chehab , linux-kernel@vger.kernel.org, Hans Verkuil , Laurent Pinchart , Sakari Ailus Subject: V4L2 device node centric - Was: [PATCH v4 6/7] media: videodev2: add a flag for MC-centric devices Message-ID: <20170828102751.76f8b93f@vento.lan> In-Reply-To: <7c8a51f6-92b7-0262-9a41-7eb28234638f@xs4all.nl> References: <638ed268ca84c5e8ea810a2c27e397ab7e90585b.1503747774.git.mchehab@s-opensource.com> <7c8a51f6-92b7-0262-9a41-7eb28234638f@xs4all.nl> Organization: Samsung X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2567 Lines: 77 Em Mon, 28 Aug 2017 11:41:58 +0200 Hans Verkuil escreveu: > > + control, and thus can't be used by **v4l2-centric** applications. > > vdev-centric > > TBD: I still think I prefer V4L2-centric over vdev-centric. I'm splitting it on a separate thread, to make easier for us to discuss. For those that aren't tracking the patchset that are documenting those terms, when MC was added, we got a hole new series of V4L2 devices that are incompatible with standard V4L2 applications, as they require knowledge about the hardware sub-devices. We are referring to such devices as MC-centric. We need another term to refer to the V4L2 devices that can be used by a generic application, and are fully controlled via a V4L2 device (/dev/video*, /dev/radio*, /dev/swradio*, /dev/vbi*, /dev/v4l-touch*). The proposed documentation patch series solves this issue by adding a glossary (patch 1) that defines what a "V4L2 device node" as: V4L2 device node A device node that it is associated to a V4L2 main driver, as specified at :ref:`v4l2_device_naming`. And, at the device naming chapter, at the spec (patch 2), it explicitly lists all V4L2 device node names: .. _v4l2_device_naming: V4L2 Device Node Naming ======================= ... The existing V4L2 device node types are: ======================== ====================================================== Default device node name Usage ======================== ====================================================== ``/dev/videoX`` Video input/output devices ``/dev/vbiX`` Vertical blank data (i.e. closed captions, teletext) ``/dev/radioX`` Radio tuners and modulators ``/dev/swradioX`` Software Defined Radio tuners and modulators ``/dev/v4l-touchX`` Touch sensors ======================== ====================================================== So, the concept of "V4L2 Device Node" is now clear, and doesn't include V4L2 sub-device device nodes (/dev/v4l-subdev*). For devices controlled via media controller, everybody seems to be comfortable of calling them as MC-centric. There are currently two proposals to refer to the media hardware that is controlled via a V4L2 Device Node: - vdev-centric - V4L2-centric The last one sounds confusing to me, as subdev API is part of the V4L2 specification. "V4L2-centric" name sounds to include subdevs. That's why IMHO, vdev-centric is better. We could go to some other naming for them, that would also be an alias for "V4L2 Device Node": - VD-centric - VDN-centric Comments? Thanks, Mauro