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Re: framebuffer overlay

I have another question.

Has there been any discussion on any type of generic framebuffer v4l2 device (output device), like a gstreamer sink (like the soc_camera)?

From this perspective, when the frame buffer registers itself, it could just *add* the capabilities, and allow the fb.c to handle many of the logistics.

I am developing for a system where we do not use X and use the framebuffer directly (E17). It would be nice to fit any of the framebuffers into a *neat* v4l2 package for any app to use (gstreamer, mplayer).

And with our camera, gstreamer, etc. could just be a command line away from live streaming :)


Dongsoo, Nathaniel Kim wrote:
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:

I am trying to write a driver for a camera using the new soc_camera in
mainline kernel the output is the overlay framebuffer (pxa270) and i
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.


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 :-)




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
needs a v4l2 device. Is this in the right ballpark?


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