How to extend Kdirve/fbdev to support overlay

Yang JianJun supermaper at
Mon Nov 13 23:47:56 PST 2006

Hi All,

    Currently, I am working on Gtk+/X for embedded system, which runs on an
Intel PXA27x processor. The LCD driver supports three frame buffer layers:
base, overlay1 and overlay2. They are /dev/fb0, /dev/fb1 and /dev/fb2 in my
system. On Xserver there is kdrive server and fbdev driver. I would like the
windowing system to make use of three layers simultaneously.
    As for a Video Capture application, the common gtk window should be
placed on fb0, the live video should be on overlay2, while the text or icon
on video should be on overlay1 for the sake of transparent effect.
    That is to say, the Gtk application should be able to create windows on
a specified layer, either one of the three frame buffers. And kdrive should
be capable of rendering the window to the correct frame buffer.
    But the fbdev driver support only one frame buffer (the base, /dev/fb0)
by default in kdrive server. Also the depth of overlay1 is 19(RGB cover 18
bit, and a transparent bit). But fbdev does not support depth 19.
    Is there any solution for this issue?

Best Regards

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