My Xserver (kdrive, Xfbdev) driver loops too quickly

Adam Jackson ajax at
Mon Jun 26 08:18:39 PDT 2006

On Sunday 25 June 2006 19:39, Orkie wrote:
> I do have a theory as to why this may be the case. Xserver as far as I can
> tell, is designed to sit and wait for mouse data (since most mice only send
> data when there is something to send) from the device file. However, since
> GPIO (the device file you read GP2X control data from) always has data, it
> keeps looping too quickly when normally, it would be waiting for data,
> casuing the server to take over the CPU (it runs at 99% CPU usage when
> nothing else is doing anything, but can only get down to around 40% even if
> other programs need the processor time more). I could be completely wrong
> about the cause of the problem of course.

No, I think you're right.  If there's no way to get an interrupt out of the 
hardware when the buttons are pressed, then you'll probably want to change 
your driver to just poll periodically.  Check out the timer code in 
os/WaitFor.c, and pick a polling frequency that you can live with.

- ajax
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