Date: Wed, 20 Aug 1997 12:41:17 +0200 (MEST) From: Søren Schmidt <sos@sos.freebsd.dk> To: j_mini@efn.org Cc: hackers@FreeBSD.ORG Subject: Re: MDA and VGA memory overlaps. Message-ID: <199708201041.MAA17982@sos.freebsd.dk> In-Reply-To: <19970820024553.03988@micron.efn.org> from Jonathan Mini at "Aug 20, 97 02:45:53 am"
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In reply to Jonathan Mini who wrote:
> I am writing a set of drivers that replaces the syscons driver and manages
> the console via two devices (and a psuedo device) where basically one device is
> the display, (write only) the other is the keyboard (read only) and then the
> psuedo device is a tty the can bind to one of each (display+keyboard pair) and
> possible more (such as a mouse) to implement a tty. Oh, I should mention that
> it would also be possible to have a tty which didn't bind a device, in that
> case it simply would never diplay anything (with no display) or never get input
> (with no keytboard), etc, etc.
Hmm, why do you need this ??, or are you trying to resolve the "great
unificated console" that was kind of designed a couble of years ago,
but never implemented ??
> Well, my problem is this : The MDA memory mapping lies INSIDE the VGA memory
> mapping. VGA uses 0xa0000-0xaffff (for graphics) and 0xb8000-0xbffff, (for
> text) and the MDA uses 0xb0000-0xb0fff. One of the goals of this is to allow a
> system to be able to have both the mda and vga devices configured, and both
> successfully probe/attach within the system.
> My question is : What do I do for memory mapping within the device
> configuration? As I see it I have three chocies :
> a) dont' trakc memory mappings within the config, as syscons does.
> b) don't track memory LENGTH, and give the vga the base of 0xa0000,
> and assume it's base+0x18000 for the position of the text buffer,
> c) make two devices for the vga.. one to handle text and one to handle
> video. I don't even want to think about device contention, although
> the solution is feasable. :(
>
> Right now I am using solution b, since it is simplest to implement.
Solution c is the only that will work, if you have a monochrome VGA
solution b breaks...
How are you going to handle the communication thats needed between the
keyboard, mouse and the video driver ??
(hints: keyboard layouts, virtual consoles, mouse support, misc ioctl's)
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Søren Schmidt (sos@FreeBSD.org) FreeBSD Core Team
Even more code to hack -- will it ever end
..
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