Date: Thu, 04 Nov 1999 22:08:56 +0900 From: Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp> To: Amancio Hasty <hasty@rah.star-gate.com> Cc: current@freebsd.org, yokota@zodiac.mech.utsunomiya-u.ac.jp Subject: Re: vga driver and signal Message-ID: <199911041308.WAA16201@zodiac.mech.utsunomiya-u.ac.jp> In-Reply-To: Your message of "Wed, 03 Nov 1999 14:23:15 PST." <199911032223.OAA39942@rah.star-gate.com> References: <199911032223.OAA39942@rah.star-gate.com>
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AFAIK, not all video cards generate the vertical retrace interrupt. Even worse, some BIOSes have a configuration option which instract the BIOS NOT to assign an IRQ to the PCI video card. I fully agree that the vertical retrace interrupt will be of great value, but I wonder if it is really worth the trouble, because it might be available in only few cards and systems at the end of the day... Well, I may be wrong :-) Kazu >Say is there anyone that can add signal delivery to the /sys/dev/fb/vga.c? >(For now any quick hack to the driver for delivering the signal will do ) > >The context is from a posting to the xfree86 mailing list: > > >keithp@suse.com said: >> You need to fit one event in per retrace. If you knew >> the phase of the sampling clock with respect to the retrace >> you could do that by skipping one sample then two then one, etc... >> But we don't know the phase and if you do that with >> arbitrary phase you end up sending two events in one retrace >> and then skipping the next and it looks worse. >> If we had a signal delivered at vertical retrace time, we could easily >> sync the mouse rate with the video rate -- run the mouse events >> through a simple filter and estimate mouse position at the vertical >> retrace interval using some forward estimation. > >> Additionally, the vertical retrace signal could be used for the double >> buffering extension to avoid tearing, and for the sync extension which >> kinda wants this. And for many video cards which can't update >> colormaps or cursor positions at other times without visible artifacts >> on the screen. > >> It would take some kernel work though; the results might well be worth >> the effort. > >> -keith > >I am too busy nowdays working :( To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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