On Wed, Oct 20, 1999 at 03:46:42PM -0700, Jon M. Taylor wrote:
> On Wed, 20 Oct 1999, [iso-8859-1] Rub�n wrote:
>
> > On 1999/Oct/20, Brian S. Julin wrote:
> >
> > > Basically there are two situations to worry about. One is trying
> > > to find the ray position from userspace when the process is running.
> > > The other is trying to get the scheduler to run the process
> > > promptly at a certain ray positions.
> >
> > I think there is an easy solution for the first thing. Why don't you
> > share a flag variable between the kernel and the process, that becomes 1 at
> > the vertical retrace and 0 when it finishes? It would be for programmers
> > even more efficient than reading from the IO port directly (which is
> > impossible under Linux, obviously). It could be managed in a similar way
> > than the graphics context, couldn't it?
>
> I think that putting this flag in the context map is the way to
> go. The flag can be quickly toggled by the interrupt handler, and nothing
> else is necessary. This doesn't get around the scheduling Hz problem, but
> that is a separate issue anyway, and needs to be fixed for a lot more than
> just GGI.
It'd be even better to increase a value every vblank so applications
can find out if it has missed any frames, and also to make sure
applications don't redraw more than once per frame.
--
Niklas
