From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751882AbdJESjv (ORCPT ); Thu, 5 Oct 2017 14:39:51 -0400 Received: from osg.samsung.com ([64.30.133.232]:47727 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751421AbdJESjt (ORCPT ); Thu, 5 Oct 2017 14:39:49 -0400 Date: Thu, 5 Oct 2017 15:39:29 -0300 From: Mauro Carvalho Chehab To: Sakari Ailus Cc: Linux Doc Mailing List , Linux Media Mailing List , Mauro Carvalho Chehab , linux-kernel@vger.kernel.org, Jonathan Corbet , Hans Verkuil , Ricardo Ribalda Delgado , laurent.pinchart@ideasonboard.com Subject: Re: [PATCH v5 1/7] media: add glossary.rst with a glossary of terms used at V4L2 spec Message-ID: <20171005153929.0433df38@recife.lan> In-Reply-To: <20171005082107.i76vntyg5ku5hqr7@valkosipuli.retiisi.org.uk> References: <65af989db9cc5479b863657add04940ae6de9d5c.1503924361.git.mchehab@s-opensource.com> <20170829074748.yldwq2gktgefzuaa@valkosipuli.retiisi.org.uk> <20170829100750.6852b64f@recife.lan> <20171005082107.i76vntyg5ku5hqr7@valkosipuli.retiisi.org.uk> Organization: Samsung X-Mailer: Claws Mail 3.15.1-dirty (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 Em Thu, 5 Oct 2017 11:21:07 +0300 Sakari Ailus escreveu: > Hi Mauro, > > My apologies for the late reply. > > On Tue, Aug 29, 2017 at 10:07:50AM -0300, Mauro Carvalho Chehab wrote: > > Em Tue, 29 Aug 2017 10:47:48 +0300 > > Sakari Ailus escreveu: > > > > > Hi Mauro, > > > > > > Thanks for the update. A few comments below. > > > > > > On Mon, Aug 28, 2017 at 09:53:55AM -0300, Mauro Carvalho Chehab wrote: > > > > Add a glossary of terms for V4L2, as several concepts are complex > > > > enough to cause misunderstandings. > > > > > > > > Signed-off-by: Mauro Carvalho Chehab > > > > --- > > > > Documentation/media/uapi/v4l/glossary.rst | 147 ++++++++++++++++++++++++++++++ > > > > Documentation/media/uapi/v4l/v4l2.rst | 1 + > > > > 2 files changed, 148 insertions(+) > > > > create mode 100644 Documentation/media/uapi/v4l/glossary.rst > > > > > > > > diff --git a/Documentation/media/uapi/v4l/glossary.rst b/Documentation/media/uapi/v4l/glossary.rst > > > > new file mode 100644 > > > > index 000000000000..0b6ab5adec81 > > > > --- /dev/null > > > > +++ b/Documentation/media/uapi/v4l/glossary.rst > > > > @@ -0,0 +1,147 @@ > > > > +======== > > > > +Glossary > > > > +======== > > > > + > > > > +.. note:: > > > > + > > > > + This goal of section is to standardize the terms used within the V4L2 > > > > + documentation. It is written incrementally as they are standardized in > > > > + the V4L2 documentation. So, it is a Work In Progress. > > > > > > I'd leave the WiP part out. > > > > IMO, it is important to mention it, as the glossary, right now, covers > > only what's used on the first two sections of the API book. There are > > a lot more to be covered. > > Works for me. > > > > > > > > > > + > > > > +.. Please keep the glossary entries in alphabetical order > > > > + > > > > +.. glossary:: > > > > + > > > > + Bridge driver > > > > + The same as V4L2 main driver. > > > > > > I've understood bridges being essentially a bus receiver + DMA. Most ISPs > > > contain both but have more than that. How about: > > > > > > A driver for a bus (e.g. parallel, CSI-2) receiver and DMA. Bridge drivers > > > typically act as V4L2 main drivers. > > > > No, only on some drivers the bridge driver has DMA. A vast amount of > > drivers (USB ones) don't implement any DMA inside the driver, as it is > > up to the USB host driver to implement support for DMA. > > > > There are even some USB host drivers that don't always use DMA for I/O > > transfers, using direct I/O if the message is smaller than a threshold > > or not multiple of the bus word. This is pretty common on SoC USB host > > drivers. > > > > In any case, for the effect of this spec, and for all discussions we > > ever had about it, bridge driver == V4L2 main driver. I don't > > see any reason why to distinguish between them. > > I think you should precisely define what a bridge driver means. Generally > ISP drivers aren't referred to as bridge drivers albeit they, too, function > as V4L2 main drivers. Btw, this is already defined, currently, at v4l2-subdev.h: * Sub-devices are devices that are connected somehow to the main bridge * device. These devices are usually audio/video muxers/encoders/decoders or * sensors and webcam controllers. * * Usually these devices are controlled through an i2c bus, but other busses * may also be used. Please notice that there it says: "main bridge" :-) Such definition was added since the beginning of the subdev concept, back in 2008 and was reviewed by several V4L core developers: commit 2a1fcdf08230522bd5024f91da24aaa6e8d81f59 Author: Hans Verkuil Date: Sat Nov 29 21:36:58 2008 -0300 V4L/DVB (9820): v4l2: add v4l2_device and v4l2_subdev structs to the v4l2 framework. Start implementing a proper v4l2 framework as discussed during the Linux Plumbers Conference 2008. Introduces v4l2_device (for device instances) and v4l2_subdev (representing sub-device instances). Signed-off-by: Hans Verkuil Reviewed-by: Laurent Pinchart Reviewed-by: Guennadi Liakhovetski Reviewed-by: Andy Walls Reviewed-by: David Brownell Signed-off-by: Mauro Carvalho Chehab Thanks, Mauro