Re: Getting started with OMAP3 ISP

[Gary Thomas <gary@mlbassoc.com>]

On 2011-08-29 04:49, Laurent Pinchart wrote:
> Hi Gary,
>
> On Thursday 25 August 2011 18:07:38 Gary Thomas wrote:
>> Background:  I have working video capture drivers based on the
>> TI PSP codebase from 2.6.32.  In particular, I managed to get
>> a driver for the TVP5150 (analogue BT656) working with that kernel.
>>
>> Now I need to update to Linux 3.0, so I'm trying to get a driver
>> working with the rewritten ISP code.  Sadly, I'm having a hard
>> time with this - probably just missing something basic.
>>
>> I've tried to clone the TVP514x driver which says that it works
>> with the OMAP3 ISP code.  I've updated it to use my decoder device,
>> but I can't even seem to get into that code from user land.
>>
>> Here are the problems I've had so far:
>>     * udev doesn't create any video devices although they have been
>>       registered.  I see a full set in /sys/class/video4linux
>>          # ls /sys/class/video4linux/
>>          v4l-subdev0  v4l-subdev3  v4l-subdev6  video1       video4
>>          v4l-subdev1  v4l-subdev4  v4l-subdev7  video2       video5
>>          v4l-subdev2  v4l-subdev5  video0       video3       video6
>
> It looks like a udev issue. I don't think that's related to the kernel
> drivers.
>
>>       Indeed, if I create /dev/videoX by hand, I can get somewhere, but
>>       I don't really understand how this is supposed to work.  e.g.
>>         # v4l2-dbg --info /dev/video3
>>         Driver info:
>>             Driver name   : ispvideo
>>             Card type     : OMAP3 ISP CCP2 input
>>             Bus info      : media
>>             Driver version: 1
>>             Capabilities  : 0x04000002
>>                     Video Output
>>                     Streaming
>>
>>     * If I try to grab video, the ISP layer gets a ton of warnings, but
>>       I never see it call down into my driver, e.g. to check the current
>>       format, etc.  I have some of my own code from before which fails
>>       miserably (not a big surprise given the hack level of those programs).
>>       I tried something off-the-shelf which also fails pretty bad:
>>         # ffmpeg -t 10 -f video4linux2 -s 720x480 -r 30 -i /dev/video2
>> junk.mp4
>>
>> I've read through Documentation/video4linux/omap3isp.txt without learning
>> much about what might be wrong.
>>
>> Can someone give me some ideas/guidance, please?
>
> In a nutshell, you will first have to configure the OMAP3 ISP pipeline, and
> then capture video.
>
> Configuring the pipeline is done through the media controller API and the V4L2
> subdev pad-level API. To experiment with those you can use the media-ctl
> command line application available at http://git.ideasonboard.org/?p=media-
> ctl.git;a=summary. You can run it with --print-dot and pipe the result to dot
> -Tps to get a postscript graphical view of your device.
>
> Here's a sample pipeline configuration to capture scaled-down YUV data from a
> sensor:
>
> ./media-ctl -r -l '"mt9t001 3-005d":0->"OMAP3 ISP CCDC":0[1], "OMAP3 ISP
> CCDC":2->"OMAP3 ISP preview":0[1], "OMAP3 ISP preview":1->"OMAP3 ISP
> resizer":0[1], "OMAP3 ISP resizer":1->"OMAP3 ISP resizer output":0[1]'
> ./media-ctl -f '"mt9t001 3-005d":0[SGRBG10 1024x768], "OMAP3 ISP
> CCDC":2[SGRBG10 1024x767], "OMAP3 ISP preview":1[YUYV 1006x759], "OMAP3 ISP
> resizer":1[YUYV 800x600]'
>
> After configuring your pipeline you will be able to capture video using the
> V4L2 API on the device node at the output of the pipeline.

Getting somewhere now, thanks.  When I use this full pipeline, I can get all
the way into my driver where it's trying to start the data.

What if I want to use less of the pipeline?  For example, I'd normally be
happy with just the CCDC output.  How would I do that?  What pixel format
would I use with ffmpeg?

n.b. I know most of these are pretty n00b questions - I'd look up the
answers for myself, but I've had precious little success finding any
documentation, especially on media-ctl and/or the OMAP3 ISP setups.

Thanks again

-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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