Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935529AbdCLV7F (ORCPT ); Sun, 12 Mar 2017 17:59:05 -0400 Received: from ec2-52-27-115-49.us-west-2.compute.amazonaws.com ([52.27.115.49]:60516 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S935360AbdCLV7A (ORCPT ); Sun, 12 Mar 2017 17:59:00 -0400 Date: Sun, 12 Mar 2017 18:58:45 -0300 From: Mauro Carvalho Chehab To: Steve Longerbeam Cc: Russell King - ARM Linux , mark.rutland@arm.com, andrew-ct.chen@mediatek.com, minghsiu.tsai@mediatek.com, nick@shmanahar.org, songjun.wu@microchip.com, Hans Verkuil , pavel@ucw.cz, shuah@kernel.org, devel@driverdev.osuosl.org, markus.heiser@darmarIT.de, laurent.pinchart+renesas@ideasonboard.com, robert.jarzmik@free.fr, geert@linux-m68k.org, p.zabel@pengutronix.de, linux-media@vger.kernel.org, devicetree@vger.kernel.org, kernel@pengutronix.de, arnd@arndb.de, tiffany.lin@mediatek.com, bparrot@ti.com, robh+dt@kernel.org, horms+renesas@verge.net.au, mchehab@kernel.org, linux-arm-kernel@lists.infradead.org, niklas.soderlund+renesas@ragnatech.se, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Sakari Ailus , jean-christophe.trotin@st.com, sakari.ailus@linux.intel.com, fabio.estevam@nxp.com, shawnguo@kernel.org, sudipm.mukherjee@gmail.com Subject: Re: [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit controls from a pipeline Message-ID: <20170312185845.5c18ffd0@vento.lan> In-Reply-To: References: <20170310120902.1daebc7b@vento.lan> <5e1183f4-774f-413a-628a-96e0df321faf@xs4all.nl> <20170311101408.272a9187@vento.lan> <20170311153229.yrdjmggb3p2suhdw@ihha.localdomain> <20170311184551.GD21222@n2100.armlinux.org.uk> <1f1b350a-5523-34bc-07b7-f3cd2d1fd4c1@gmail.com> <20170311185959.GF21222@n2100.armlinux.org.uk> <4917d7fb-2f48-17cd-aa2f-d54b0f19ed6e@gmail.com> <20170312073745.GI21222@n2100.armlinux.org.uk> 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: 5066 Lines: 120 Em Sun, 12 Mar 2017 10:56:53 -0700 Steve Longerbeam escreveu: > On 03/11/2017 11:37 PM, Russell King - ARM Linux wrote: > > On Sat, Mar 11, 2017 at 07:31:18PM -0800, Steve Longerbeam wrote: > > Given what Mauro has said, I'm convinced that the media controller stuff > > is a complete failure for usability, and adding further drivers using it > > is a mistake. I never said that. The thing is that the V4L2 API was designed in 1999, when the video hardware were a way simpler: just one DMA engine on a PCI device, one video/audio input switch and a few video entries. On those days, setting up a pipeline on such devices is simple, and can be done via VIDIOC_*_INPUT ioctls. Nowadays hardware used on SoC devices are a way more complex. SoC devices comes with several DMA engines for buffer transfers, plus video transform blocks whose pipeline can be set dynamically. The MC API is a need to allow setting a complex pipeline, as VIDIOC_*_INPUT cannot work with such complexity. The subdev API solves a different issue. On a "traditional" device, we usually have a pipeline like: