How to write an X driver..?

[Florian Echtler]

> > I think that this is generally done by having the framebuffer driver
> > allocate the screen to be as large as possible.  Then in the xserver
> > you know that offscreen memory address is simply from the end of the
> > visible screen.
> But does the device support any form of acceleration ? If not, I'd go
> with a shadowfb approach instead (which can be pretty efficient these
> days).
I guess that depends on how you define acceleration, but it doesn't do
much in any case. What it can do is internal copying of memory blocks,
and run-length encoding of pixel data (so you could say that it supports
accelerated drawing of horizontal lines :-).

But can you explain "shadowfb approach" in more detail? I've seen the
phrase in the fbdrv manual already; does that mean that the X driver
maintains a copy of the framebuffer content in memory and only tries to
transmit changed regions? Could you still take advantage of the internal
block copying with that approach?

Florian
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