How to catch display blanking interval?

[Jeffrey Mulligan]

I am trying to synchronize the updating of a display on the SUN-4/110
console with the display refresh.  In cgfour(4S), the following sentence
appears in the discussion of the ioctl FBIOPUTCMAP:

	The driver uses color board vertical-retrace interrupts to
	load the color map.

I had hoped that this ioctl would cause the program to hang until the
retrace interval, but this does not seem to happen.  I assume that the
ioctl causes the color map change to be queued, and that the hardware gets
loaded by the interrupt handler.

I also turned up the following lines in /usr/include/sun/fbio.h :

/* Vertical retrace support. */
#define FBIOVERTICAL	_IOW(F, 9, int)

What the heck is this for???  I tried calling ioctl with this code, and
nothing happened (i.e., no delays, no data returned).

I remember a few months back there was a long posting on undocumented
features of the sun framebuffer from someone who was hacking their own
operating system.  I'm sure what I want to do can be done, but I'd like to
do it in the approved fashion if possible.

	Jeff Mulligan (jbm at aurora.arc.nasa.gov)
	NASA/Ames Research Ctr., Mail Stop 239-3, Moffet Field CA, 94035
	(415) 694-6290