Michel Dänzer <[EMAIL PROTECTED]> writes:
> On Fre, 2002-11-01 at 21:10, [EMAIL PROTECTED] wrote:
> > Yes, XSYNC has the right things to allow applications to synchronize
> > on arbitrary things (including vertical sync).
> >
> > If the fbdev and/or DRI folks are willing to support and export an interface,
> > it should be possible to get the plumbing hooked up.
> >
> > Just make it a file descriptor we (and/or other things) can select against,
> > and it should be something that can be pretty cross platform without much
> > trouble: them's that don't implement it on a given platform won't get
> > support...
>
> The interface we've implemented in the DRM is an ioctl which basically
> blocks for a requested number of vertical blanks (it's more flexible in
> fact). Maybe a daemon or something could provide a file descriptor to
> select against?
Both select and a blocking ioctl are really the wrong interface
here.
select() or poll() are problematical because select() waits for a
condition, not an event. That is, these function calls are designed
things like "tell me when there is more data to read".
The blocking ioctl is a pain because it means you have to devote a
thread to waiting for the VBI; but it at least is well defined.
Unix signals are another possibility - a real pain to program,
but at least they were designed for things like this. "Tell me
when the next VBI occurs" has very similar semantics to
alarm(2).
Regards,
Owen
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