From mboxrd@z Thu Jan 1 00:00:00 1970 From: slongerbeam@gmail.com (Steve Longerbeam) Date: Sat, 18 Feb 2017 09:29:17 -0800 Subject: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and getting of frame rates In-Reply-To: <20170218092335.GI21222@n2100.armlinux.org.uk> 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> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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