[libcamera-devel] [RFC PATCH 08/10] libcamera: v4l2_videodevice: Create color-format planes in CreateBuffer()

[Nicolas Dufresne]

Le jeudi 26 août 2021 à 14:08 +0300, Laurent Pinchart a écrit :
> > We'll probably have to carry a downstream patch to handle them
> > initially... Would it be possible to at least make it easy to do that
> > until proper V4L2 support gets merged?
> > 
> > (v4l2_ext API is being worked on, but last time I checked it was stuck
> > in review, without any comments...)
> 
> If there's significant progress with this development we can carry a
> downstream patch to avoid waiting for the API to be merged upstream, but
> it indeed seems stuck. What would be your use case for such a downstream
> patch though ? We would need drivers using the API to make it useful in
> libcamera.

I've come across a potential usage of this, but that was too much work to fix
back then. The thingy was a very low power camera viewer (in a grid). We wanted
to get all the requested frames into the same DMABuf, for that we could have had
to be able to import that DMABuf with customized offsets and strides, so that
the camera (if capable) would write the frame at the appropriate location in the
frame. With 100% of the v4l2 driver not accepting custom strides, and this
import limitation, we gave up, and simply reduced the grid size due to memory
limitation.

Nicolas