[PATCH RFC] media: staging/imx: fix complete handler

[Steve Longerbeam]

On 10/01/2017 04:36 PM, Russell King - ARM Linux wrote:
> On Sun, Oct 01, 2017 at 01:16:53PM -0700, Steve Longerbeam wrote:
>> Right, imx_media_add_vdev_to_pa() has followed a link to an
>> entity that imx is not aware of.
>>
>> The only effect of this patch (besides allowing the driver to load
>> with smiapp cameras), is that no controls from the unknown entity
>> will be inherited to the capture device nodes. That's not a big deal
>> since the controls presumably can still be accessed from the subdev
>> node.
> smiapp is just one example I used to illustrate the problem.  The imx
> media implementation must not claim subdevs exclusively for itself if
> it's going to be useful, it has to cater for subdevs existing for
> other hardware attached to it.
>
> As you know, the camera that interests me is my IMX219 camera, and it's
> regressed with your driver because of your insistence that you have sole
> ownership over subdevs in the imx media stack

If by "sole ownership", you mean expecting async registration of subdevs
and setting up the media graph between them, imx-media will only do that
if those devices and the connections between them are described in the
device tree. If they are not, i.e. the subdevs and media pads and links are
created internally by the driver, then imx-media doesn't interfere with 
that.

But I agree your patch is a fix for a regression. It was created during some
final tweaks to the control inheritance code.


>   - I'm having to carry more
> and more hacks to workaround things that end up broken.  The imx-media
> stack needs to start playing better with the needs of others, which it
> can only do by allowing subdevs to be used by others.

Well, for example imx-media will chain s_stream until reaches your
IMX219 driver. It's then up to your driver to pass s_stream to the
subdevs that it owns.

>    One way to
> achieve that change that results in something that works is the patch
> that I've posted - and tested.

  Can you change the error message to be more descriptive, something
like "any controls for unknown subdev %s will not be inherited\n" and maybe
convert to a warn. After that I will ack it.

> The reason that the IMX219 driver users subdevs is because it's capable
> of image cropping and binning on the camera module - which helps greatly
> if you want to achieve higher FPS for high speed capture [*].
>
> It also results in all controls (which are spread over the IMX219's two
> subdevs) to be visible via the v4l2 video interface - I have all the
> controls attached to the pixel array subdev as well as the controls
> attached to the scaling subdev.
>
>> However, I still have some concerns about supporting smiapp cameras
>> in imx-media driver, and that is regarding pad indexes. The smiapp device
>> that exposes a source pad to the "outside world", which is either the binner
>> or the scaler entity, has a pad index of 1. But unless the device tree port
>> for the smiapp device is given a reg value of 1 for that port, imx-media
>> will assume it is pad 0, not 1.
> For IMX219, the source pad on the scaler (which is connected to the CSI
> input pad) is pad 0 - always has been.  So I guess this problem is hidden
> because of that choice.  Maybe that's a problem for someone who has a
> SMIAPP camera to address.

I'm working on a patch for smiapp.

Steve

>
> Right now, my patch stack to get the imx219 on v4.14-rc1 working is:
>
> media: staging/imx: fix complete handler
> [media] v4l: async: don't bomb out on ->complete failure
> media: imx-csi: fix burst size
> media: imx: debug power on
> ARM: dts: imx6qdl-hummingboard: add IMX219 camera
> media: i2c: imx219 camera driver
> media: imx: add frame intervals back in
> fix lp-11 timeout
>
> The frame interval patch is there because I just don't agree with the
> position of the v4l2 folk, and keeping it means I don't have to screw
> up my camera configuration scripts with special handling.  The
> "fix lp-11 timeout" changes the LP-11 timeout to be a warning rather
> than a failure - and contary to what FSL/NXP say, it works every time
> on the iMX6 devices without needing to go through their workaround.
>
>
> * - This is the whole reason I bought the IMX219, and have written the
> IMX219 driver.  I want to use it for high speed capture of an arrow
> leaving a recurve bow.  Why?  Everyone archer shoots subtly differently,
> and I want to see what's happening to the arrows that are leaving my
> bow.  However, for that to be achievable, I (a) need a working capture
> implementation for imx6, and (b) I need to be able to quickly convert
> bayer to an image, and (c) I need to either encode it on the fly, or
> write the raw images to SSD.
>
> (a) is thwarted by the breakage I keep stumbling over with the capture
> code.
>
> (b) I have using the GC320 GPU and a gstreamer plugin, trivially
> converting the bayer data to grayscale.
>
> (c) I've yet to achieve - encoding may be supported by the CODA v4l
> driver, but nothing in userspace appears to support it, there's no
> gstreamer v4l plugin for encoding, only one for decoding.  I also
> suspect at either the 16G I have free on the SSD will get eaten up
> rapidly without encoding, or the SSD may not keep up with the data
> rate.
>
> Right now, all my testing is around displaying on X:
>
> DISPLAY=:0 gst-launch-1.0 -v v4l2src device=/dev/video9 io-mode=4 ! bayer2rgbgc ! clockoverlay halignment=2 valignment=1 ! xvimagesink
>