Date: Sat, 4 Feb 1995 04:54:49 -0500 From: starkhome!gene@sbstark.cs.sunysb.edu (Gene Stark) To: Mark Tinguely <plains.nodak.edu!tinguely@sbstark.cs.sunysb.edu> Cc: hackers@FreeBSD.org Subject: longjump in kernel Message-ID: <199502040954.EAA04655@starkhome.cs.sunysb.edu> In-Reply-To: Mark Tinguely's message of Fri, 3 Feb 1995 20:24:58 -0600
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> stupid question time. I have a video board that requires the camera to > supply vertical sync, and I need to wait for starts/stops of the vertical > syncs in the driver. if the camera is turned off and someone reads from the > camera, then my driver will hang forever (I guess this could be said for a > disk drive, but more users will shut their camera off when they would not > shut off their disk drive). > > am I correct in think there is nothing that can be done in this situation? > (a user process can set a timer and long jump out, but I can imagine this > is leagal in a device driver). Have a look at /sys/i386/isa/tw.c, which syncs to zero crossings of the AC power line. You should be able to use similar techniques to solve your problem. - Gene Stark
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