From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753828AbdBRR30 (ORCPT ); Sat, 18 Feb 2017 12:29:26 -0500 Received: from mail-pg0-f65.google.com ([74.125.83.65]:36324 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753742AbdBRR3V (ORCPT ); Sat, 18 Feb 2017 12:29:21 -0500 Subject: Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and getting of frame rates To: Russell King - ARM Linux References: <1487211578-11360-1-git-send-email-steve_longerbeam@mentor.com> <1487211578-11360-30-git-send-email-steve_longerbeam@mentor.com> <24d42948-a77d-445f-e3e9-ab595b0cfc3e@gmail.com> <20170218092335.GI21222@n2100.armlinux.org.uk> Cc: robh+dt@kernel.org, mark.rutland@arm.com, shawnguo@kernel.org, kernel@pengutronix.de, fabio.estevam@nxp.com, mchehab@kernel.org, hverkuil@xs4all.nl, nick@shmanahar.org, markus.heiser@darmarIT.de, p.zabel@pengutronix.de, laurent.pinchart+renesas@ideasonboard.com, bparrot@ti.com, geert@linux-m68k.org, arnd@arndb.de, sudipm.mukherjee@gmail.com, minghsiu.tsai@mediatek.com, tiffany.lin@mediatek.com, jean-christophe.trotin@st.com, horms+renesas@verge.net.au, niklas.soderlund+renesas@ragnatech.se, robert.jarzmik@free.fr, songjun.wu@microchip.com, andrew-ct.chen@mediatek.com, gregkh@linuxfoundation.org, shuah@kernel.org, sakari.ailus@linux.intel.com, pavel@ucw.cz, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, devel@driverdev.osuosl.org From: Steve Longerbeam Message-ID: Date: Sat, 18 Feb 2017 09:29:17 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170218092335.GI21222@n2100.armlinux.org.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/18/2017 01:23 AM, Russell King - ARM Linux wrote: > On Fri, Feb 17, 2017 at 05:12:44PM -0800, Steve Longerbeam wrote: >> Hi Russell, >> >> I signed-off on this but after more review I'm not sure this is right. >> >> The CSI-2 receiver really has no control over frame rate. It's output >> frame rate is the same as the rate that is delivered to it. >> >> So this subdev should either not implement these ops, or it should >> refer them to the attached source subdev. > > Where in the V4L2 documentation does it say that is permissible? > https://www.linuxtv.org/downloads/v4l-dvb-apis-old/vidioc-subdev-g-frame-interval.html "The frame interval only makes sense for sub-devices that can control the frame period on their own. This includes, for instance, image sensors and TV tuners. Sub-devices that don't support frame intervals must not implement these ioctls." > If you don't implement these, media-ctl fails to propagate _anything_ > to the next sink pad if you specify a frame rate, because media-ctl > throws an error and exits immediately. > But I agree with you here. I think our only option is to ignore that quoted requirement above and propagate [gs]_frame_interval all the way to the CSI (which can control the frame rate via frame skipping). Steve