On Sat, Feb 18, 2017 at 09:29:17AM -0800, Steve Longerbeam wrote: > 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." That sounds clear - but the TV tuner example seems odd - the frame rate is determined at transmission time, not reception time. Yes, it's possible to skip frames (which would be scaling) but you can't _control_ the frame rate per se. > >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). Sounds like something to tackle the media maintainers over - the documentation vs media-ctl seem to have different ideas on this point. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
