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Re: framebuffer overlay

On Wed, Aug 12, 2009 at 5:56 PM, Ryan Raasch<ryan.raasch@xxxxxxxxx> wrote:
> 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

So, that means you need a SoC hardware based reference code right?
(because pxa is also a SoC)
I think there is not so many choices that you can put on the table.
In my experience, OMP3 camera interface is supporting overlay feature
through omap_vout I guess. I think it is not obvious in SoC H/W
platform about *what is overlay device* and *how to use* them.

And about omap3 camera interface driver, it is not in the mainline
kernel yet. For the camera interface code you need to look into
Sakari's gitorious repository and for omap_vout you need to look for
Hardik's repository or any repository he is working on..I guess.
I'm also trying to figure out the best way to use overlay feature on
samsung's new cpu named S5PC1XX.

The most complicated part of this job is the whole thing is happening
in a single piece of chip and need to figure out the standardized way
for compatibility. I wish you luck :-)


>> 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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DongSoo, Nathaniel Kim
Mobile S/W Platform Lab.
Digital Media & Communications R&D Centre
Samsung Electronics CO., LTD.
e-mail : dongsoo.kim@xxxxxxxxx

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