From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lb1-smtp-cloud7.xs4all.net ([194.109.24.24]:59588 "EHLO lb1-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965954AbeF1MrN (ORCPT ); Thu, 28 Jun 2018 08:47:13 -0400 Subject: Re: [PATCH v2 2/2] v4l: Add support for STD ioctls on subdev nodes To: Mauro Carvalho Chehab , =?UTF-8?Q?Niklas_S=c3=b6derlund?= Cc: linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org References: <20180517143016.13501-1-niklas.soderlund+renesas@ragnatech.se> <20180517143016.13501-3-niklas.soderlund+renesas@ragnatech.se> <20180628083732.3679d730@coco.lan> From: Hans Verkuil Message-ID: <536a05bd-372e-a509-a6b6-0a3e916e48ae@xs4all.nl> Date: Thu, 28 Jun 2018 14:47:05 +0200 MIME-Version: 1.0 In-Reply-To: <20180628083732.3679d730@coco.lan> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-media-owner@vger.kernel.org List-ID: On 06/28/18 13:37, Mauro Carvalho Chehab wrote: > Em Thu, 17 May 2018 16:30:16 +0200 > Niklas Söderlund escreveu: > >> There is no way to control the standard of subdevices which are part of >> a media device. The ioctls which exists all target video devices >> explicitly and the idea is that the video device should talk to the >> subdevice. For subdevices part of a media graph this is not possible and >> the standard must be controlled on the subdev device directly. > > Why isn't it possible? A media pipeline should have at least a video > devnode where the standard ioctls will be issued. Not for an MC-centric device like the r-car or imx. It's why we have v4l-subdev ioctls for the DV_TIMINGS API, but the corresponding SDTV standards API is missing. And in a complex scenario there is nothing preventing you from having multiple SDTV inputs, some of which need PAL-BG, some SECAM, some NTSC (less likely) which are all composed together (think security cameras or something like that). You definitely cannot set the standard from a video device. If nothing else, it would be completely inconsistent with how HDMI inputs work. The whole point of MC centric devices is that you *don't* control subdevs from video nodes. Regards, Hans > So, I don't see why you would need to explicitly set the standard inside > a sub-device. > > The way I see, inside a given pipeline, all subdevs should be using the > same video standard (maybe except for a m2m device with would have some > coded that would be doing format conversion). > > Am I missing something? > > Thanks, > Mauro >