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Re: framebuffer overlay




Thanks for the reply!

Dongsoo, Nathaniel Kim wrote:
On Wed, Aug 12, 2009 at 5:25 PM, Ryan Raasch<ryan.raasch@xxxxxxxxx> wrote:
Hello,

I am trying to write a driver for a camera using the new soc_camera in the
mainline kernel the output is the overlay framebuffer (pxa270) and i would
like to use the overlay output feature of v4l2 framework, but the
framebuffer does not expose itself as a output device (not yet).

Hi Ryan,

As far as I know the framebuffer of PXA2 even PXA3 can't be
categorized in a overlay device.

The pxa2 and pxa3 both have 3 framebuffers (4 if hardware curser included). There is the main fb, and 2 overlay framebuffers.

The overlay 2 has hardware accelerated ycbcr decoding (which i use now with a camera using dma). And the overlay 1 can be used only with the various types of RGB.

We have a solution which uses dma to copy the captured video from the camera sensor (mmap'd), directly to the mmap'd memory of the overlay. All occuring without user intervention.


To be able to get used as overlay device by camera interface, I think
there should be a direct FIFO between camera and framebuffer which
means there is no need to copy memory from camera to fb. But
unfortunately PXA architecture is not supporting this kind of feature.

With the above there is no need for FIFO, the dma is directly copying the received camera data to the selected framebuffer.

Ryan

Cheers,



Nate

Are there any fb that i can use as an example for this?

From looking at the driver code, it seems like the generic code of fbmem.c
needs a v4l2 device. Is this in the right ballpark?

Thanks,
Ryan

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