RE: [OpenBIOS] Video

[Wallace I. Kroeker]

There has been great discussion on video here so I decided to see how the
video was handled in the linux kernel.  Sure enough they use "int 0x10" to
handle the video setup etc.  The code does detection of the video type (e.g.
looks for EGA/VGA) and sets things up appropriately and then continues to
use the "int 0x10" calls to actually output some of the fine linux boot
messages.

As for the use of the full 256K region I suspect we will run into a lot of
other conflicts with cards other than video cards.  The bios that is built
into these cards (video, m-systems disk on a chip) expect that they will
live in the C0000 to C8000 region (from what I've read).
Someone can correct me if I'm wrong but we have to avoid using this area if
we want things to work with these different cards.

As for PCI initialization stuff you may want to check out the Ralf Brown
page.  He has a very nice piece of software that finds all your PCI devices
with lots of information on the devices.
http://www.cs.cmu.edu/afs/cs.cmu.edu/user/ralf/pub/WWW/files.html
This has his interrupt list AND "RBpciv1.19 - PCI device info program".

We should be able to use some parts of this code to enumerate the PCI for
setting up the information on the attached devices.

Also, the following book is very good and worth purchasing:
PCI Hardware and Software, 4th Ed.
by Edward Solari and George Willse
ISBN  0-929392-59-0
http://www.annabooks.com/fx020064.htm

I am starting to look into the System Management Bus to determine memory
size.  If anyone has any code that is doing this already that would be
appreciated.

My status:
I have my the OpenBIOS booting the 440BX with a set amount of memory but
haven't got a small enough linux payload which would fit in the legal BIOS
area of my machine.  The video and serial is working to allow me to interact
with the basic openbios.  I am looking at implementing enough of the BIOS
floppy to at least do a load from floppy for the time being.  I have tried
this in a minimal system but am waiting for another flash chip so that I can
do some live testing.  I compared my memory setup with the code that Ron
provided and they are basically identical although I haven't confirmed this
with total boot from a flashed bios (later this week hopefully).

Wallace
> -----Original Message-----
> From:	Ronald G. Minnich [SMTP:[e-mail]]
> Sent:	Monday, February 21, 2000 11:13 AM
> To:	[e-mail]
> Subject:	Re: [OpenBIOS] Video
>
> the second device on the bridge is in essence a dedicated pci bus for the
> graphics hardware.
>
> ron
>
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Video

[Ronald G. Minnich]

On Mon, 21 Feb 2000, Wallace I. Kroeker wrote:
> There has been great discussion on video here so I decided to see how the
> video was handled in the linux kernel.  Sure enough they use "int 0x10" to
> handle the video setup etc.  The code does detection of the video type (e.g.
> looks for EGA/VGA) and sets things up appropriately and then continues to
> use the "int 0x10" calls to actually output some of the fine linux boot
> messages.

Yes, but very early in the real kernel they stop using int10. In fact, 
after they switch to protected mode int10 is gone.
> As for the use of the full 256K region I suspect we will run into a lot of
> other conflicts with cards other than video cards.  The bios that is built
> into these cards (video, m-systems disk on a chip) expect that they will
> live in the C0000 to C8000 region (from what I've read).
> Someone can correct me if I'm wrong but we have to avoid using this area if
> we want things to work with these different cards.

You can use it all if you're in protected mode. That's why I'd like to see
openbios move to protected mode much earlier. Then you have a 2M window
(1M curently in use) from 0xfff00000 -> 0xffffffff
> As for PCI initialization stuff you may want to check out the Ralf Brown
> page.  He has a very nice piece of software that finds all your PCI devices
> with lots of information on the devices.

Linux can do this now, but I'll look anyway -- thanks
> We should be able to use some parts of this code to enumerate the PCI for
> setting up the information on the attached devices.

Absolutely.
> I have my the OpenBIOS booting the 440BX with a set amount of memory but
> haven't got a small enough linux payload which would fit in the legal BIOS
> area of my machine.

Wallace, take a good look at the high-memory bios support. I'm loading
into the 1M flash and gunzipping from it. YOu just want to get to
protected mode.

I just broke SDRAM again so I won't post my code just yet :-)

ron

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