On Thursday 17 March 2005 23:31, Timothy Miller wrote: > On Thu, 17 Mar 2005 23:16:13 -0500, Daniel Phillips <[EMAIL PROTECTED]> wrote: > > > Updating cursor glyph in interrupt context while DMA is going on. > > > Note that the latency for that could be evil. > > > > It is also a dodgy/evil thing to do. How do you know you're not > > interrupting another cursor glyph update? I would strongly suggest > > that if an interrupt routine wants to update the cursor, it should > > use interprocess communication to have a foreground task do it, or > > use a work queue. We are talking about microscopic latency here. > > I had mentioned earlier that updating the cursor glyph might be > something we would do ONLY in interrupt context.
Sorry, I missed that. Why? > I wasn't clear. When I say that the GPU "polls the write pointer", I > mean, "the GPU does a DMA read of a word in host memory that contains > the write pointer". This would be the mode where the write pointer > is not updated in the GPU by a PIO but rather where the GPU reads the > write pointer only at the most convenient and necessary times. I don't see any issue with just having the write pointer be a PIO. This is simple and effective, and the driver can worry about not poking it more often than necessary. Regards, Daniel _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
