Hi,
I'm starting to look at writing a gfxdriver for the PXA27x platform (ARM
Xscale). I don't see any guides at direct.org for writing a new
gfxdriver though, is there any such documentation? Maybe a skeleton
driver to start from?
The PXA27x supports 3 layers, a base layer and 2 overlays. The 2nd
overlay supports YUV-->RGB color conversion. Alpha blending of the
layers is also supported. But I don't see any info in the PXA27x
developer's manual about h/w blitting support, such as a
screen-to-screen copy. So doesn't look like h/w blitting is available,
atleast through the graphics controller. There is a DMA engine that can
do memory-to-memory transfers with strides, but it's not part of the
graphics controller, ie. the registers are not part of the graphics
controller register block. It's possible to add custom ioctl's to the
linux fb driver to make use of the DMA engine to do blitting, and the
gfxdriver could call those ioctl's, but that would involve a system call
per blit, which probably negates most of the cpu savings of h/w blitting.
There is a linux framebuffer driver for the PXA27x. It supports the
overlays by registering a framebuffer device for each overlay, ie.
/dev/fb/0, /dev/fb/1, /dev/fb/2. How would DirectFB deal with this,
would it detect overlays because it sees multiple framebuffer devices?
Also, the linux fb driver is not using the alpha blending support.
Given all that, do you think it's still worth-while to write a gfxdriver
for the PXA27x?
Thanks,
Steve
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