Re: [PATCH v4 29/36] media: imx: mipi-csi2: enable setting and getting of frame rates

[Steve Longerbeam]

On 02/20/2017 02:56 PM, Steve Longerbeam wrote:
> On 02/20/2017 02:04 PM, Sakari Ailus wrote:
> > Hi Steve,
> >
> > On Wed, Feb 15, 2017 at 06:19:31PM -0800, Steve Longerbeam wrote:
> > > From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
> > >
> > > Setting and getting frame rates is part of the negotiation mechanism
> > > between subdevs.  The lack of support means that a frame rate at the
> > > sensor can't be negotiated through the subdev path.
> >
> > Just wondering --- what do you need this for?
>
>
> Hi Sakari,
>
> i.MX does need the ability to negotiate the frame rates in the
> pipelines. The CSI has the ability to skip frames at the output,
> which is something Philipp added to the CSI subdev. That affects
> frame interval at the CSI output.
>
> But as Russell pointed out, the lack of [gs]_frame_interval op
> causes media-ctl to fail:
>
> media-ctl -v -d /dev/media1 --set-v4l2
> '"imx6-mipi-csi2":1[fmt:SGBRG8/512x512@1/30]'
>
> Opening media device /dev/media1
> Enumerating entities
> Found 29 entities
> Enumerating pads and links
> Setting up format SGBRG8 512x512 on pad imx6-mipi-csi2/1
> Format set: SGBRG8 512x512
> Setting up frame interval 1/30 on entity imx6-mipi-csi2
> Unable to set frame interval: Inappropriate ioctl for device (-25)Unable
> to setup formats: Inappropriate ioctl for device (25)
>
>
> So i.MX needs to implement this op in every subdev in the
> pipeline, otherwise it's not possible to configure the
> pipeline with media-ctl.


Hi Russell,

But Sakari brings up a good point. The mipi csi-2 receiver doesn't
have any control over frame rate, so why do you even need to
give it this information via media-ctl?

Steve