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To: Nate Williams <nate@mt.sri.com>
Cc: cvs-all@freebsd.org, cvs-sys@freebsd.org,
        yokota@zodiac.mech.utsunomiya-u.ac.jp
Subject: Re: cvs commit: src/sys/i386/isa syscons.c 
In-Reply-To: Your message of "Sat, 04 Apr 1998 10:33:41 MST."
             <199804041733.KAA27766@mt.sri.com> 
References: <199804041626.IAA06737@freefall.freebsd.org>  <199804041733.KAA27766@mt.sri.com> 
Date: Sun, 05 Apr 1998 09:55:41 +0900
From: Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
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>> yokota      1998/04/04 08:26:54 PST
>> 
>>   Modified files:
>>     sys/i386/isa         syscons.c 
>>   Log:
>...
>>   Video mode switch fixes:
>>   - Stop the screen saver when changing video modes.
>>   - Enclose the critical section with a pair of spltty()/splx().
>>   - A kludge to prevent scrn_update() from accessing video memory in less-
>>     critical sections in video mode change; artificially turn on the
>>     UNKNOWN_MODE flag.
>
>Is it possible that these fixes could cause the 'hang switching' bugs
>that occur when swapping virtual screens when X is starting up?

Um, I don't know. The above change affects video mode switch invoked
by ioctl. The X server tells syscons that it is entering graphics mode,
but actual mode switch is done by the X server rather than by syscons,
as you know.

>(BTW - SCO has *exactly* the same problem, so syscons is doing a better
>job of emulating it than most would expect, even the bugs. :)
>
>nate

The cause of vairous troubles with switching virtual consoles when X is
starting/exiting/resetting seems to be, in part, in syscons, but, in
other part, in the X server too.  There are cases that XFree86 servers
do not respond properly to the console switching API sequence.  At
least that was the conclusion which I and a -current user had reached
a few months ago after quite a few tests.  But, we don't know the
correct fix for the X server and syscons yet ;-<

Kazu