[maemo-developers] DSP framebuffer access

[From: Simon Pickering]

> > The screen changes colour, though it appears that the 
> screen updates 
> > only happen from time to time so exactly what changes colour, which 
> > colour it turns, and when is a question of luck.  I'm not sure how 
> > one should force an update (And perhaps this will have to 
> be from the 
> > ARM side, I don't know). Any suggestions?
> 
> Well no real improvement, but perhaps I need to produce a window that 
> won't auto-refresh itself.

I've finally got back to looking at this. Lo and behold, a bit of tweaking
(and further reading the kernel source) and it works. This is for the 770
only, the N8x0 code is causing troubles (as it doesn't have a mapped
framebuffer by default and it doesn't like mapping one, yet...). I'm working
on this and will post my conclusions one way or the other.

The changes I've made are to create a blank X11 window to display the output
(code borrowed from the Maemo mplayer code, thanks Siarhei), and to use the
kfunc() call (properly) to force the changes to be made. This call takes as
one of its arguments a structure containing x,y,width,height and format of
the update region.

This code still contains some unused variables (from my previous testing),
I'll tidy these up later on, but other than emitting compiler messages they
don't have any effect.

http://people.bath.ac.uk/enpsgp/nokia770/dsp/framebuffer_demos/770/

Cheers,


Simon