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Hi,
I have Similar questions as below, Have anybody done this ,or
give me some advices
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?
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