media: i2c: mt9p031: HFLIP/VFLIP changes format

media: i2c: mt9p031: HFLIP/VFLIP changes format

[Florian Neuhaus]

Hi Laurent

In the mt9p031 driver, the picture can be flipped either horizontally
or vertically by using the according V4L2 controls. This can be done
at runtime.
I have noticed, that flipping the picture will change the bayer-pattern.
So if I flip horizontally and vertically to get a 180 degree rotation
the bayer pattern changes from
V4L2_MBUS_FMT_SGRBG12_1X12
to
V4L2_MBUS_FMT_SGBRG12_1X12
I'm not sure how the patch should look like...
The format code could be adapted accordingly to the flipping, but
how does the userspace notices this change? The user could issue
another get_format. But what about the omap3isp-pipe?
Concrete:
What should I do to configure a streaming pipe with a flipped image?
Flip the image on the v4l-subdev and then build the pipe?
Is there a chance to propagate the format change through the pipe
during streaming?

Thanks for your clarification!

Regards,
Florian

Re: media: i2c: mt9p031: HFLIP/VFLIP changes format

[Laurent Pinchart]

Hi Florian,

On Friday 21 June 2013 15:48:25 Florian Neuhaus wrote:
> Hi Laurent
> 
> In the mt9p031 driver, the picture can be flipped either horizontally or
> vertically by using the according V4L2 controls. This can be done at
> runtime.
> I have noticed, that flipping the picture will change the bayer-pattern.
> So if I flip horizontally and vertically to get a 180 degree rotation
> the bayer pattern changes from
> V4L2_MBUS_FMT_SGRBG12_1X12
> to
> V4L2_MBUS_FMT_SGBRG12_1X12
> I'm not sure how the patch should look like...
> The format code could be adapted accordingly to the flipping, but
> how does the userspace notices this change? The user could issue
> another get_format. But what about the omap3isp-pipe?
> Concrete:
> What should I do to configure a streaming pipe with a flipped image?
> Flip the image on the v4l-subdev and then build the pipe?
> Is there a chance to propagate the format change through the pipe
> during streaming?

There are two ways to handle this situation. You could modify the output 
format, which would then bring format propagation issues, or you could offset 
the sensor crop rectangle by one pixel. The second option is probably easier 
to implement as it's local to the sensor, without any need to propagate format 
changes.

-- 
Regards,

Laurent Pinchart