Via bios code on public ftp: ftp://ftp.via.com.tw/public/sw/
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Ron, Everything I can find tells me that we should let the video card initialize itself. It looks like we should scan C0000 through E0000 for the video cards signature and then call its code.. The problem is that I think we may have to do this in 16 bit mode. Can't we get a 16-bit mode C compiler (or even better, a 16-bit mode gnu assembler)? - James
The ROM BIOS, on a system startup, executes the POST (power-on self-test) routine which usually checks memory, establishes devices etc. The POST routine also fills in the BIOS memory area at 0000:0040h and sets up the real mode interrupt handlers (those connected to IRQ lines are set to dummy handlers which simply acknowledge the interrupt with the PIC and return, those assigned to BIOS services are set to the appropriate address, which may vary with the BIOS manufacturer and revision). The POST then checks for extensions ROMs at this point (for example the video card). Absolute addresses C0000h through E0000h are searched in 2KB increments for the signature 55h 0AAh. If the signature is found, the next byte is a length indicator for the ROM (in 512 byte blocks) and the next bytes contain a FAR CALLable address (it should be called as an empirical address, with the lowest possible offset value. For example, absolute address C0003h is called as C000:0003h). The extension BIOSes perform initialization and then return. On entry, SS:SP must be set up as a valid stack.
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Well, I still am going to be stubborn about this. X11 servers manage to drive the cards pretty extensively with no real trouble.
Besides, recall on most motherboards with built-in-video: the video bios is in the nvram I just over-wrote with Linux. We have to figure this out. OpenBIOS is going to have to figure it out too, for the same reason, unless Open BIOS wants to be 1/2-Open. So let's work it out.
ron
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Well, I still am going to be stubborn about this. X11 servers manage to drive the cards pretty extensively with no real trouble.
That is because the VGA BIOS has already been run during POST, before the kernel or the X11 server ever gets loaded into the machine.
Besides, recall on most motherboards with built-in-video: the video bios is in the nvram I just over-wrote with Linux. We have to figure this out. OpenBIOS is going to have to figure it out too, for the same reason, unless Open BIOS wants to be 1/2-Open. So let's work it out.
Talk to the XFree86 4.0 guys; they're tackling the problem right now because they want to handle multi-headed machines, and (except for certain double headed products from people like Matrox) only one card can occupy the legacy ISA address area so extra cards never have their VGA BIOS' run at all.
Todd Whitesel toddpw @ best.com - To unsubscribe: send mail to majordomo@freiburg.linux.de with 'unsubscribe openbios' in the body of the message
On Fri, 18 Feb 2000, Todd Whitesel wrote:
Talk to the XFree86 4.0 guys; they're tackling the problem right now because they want to handle multi-headed machines, and (except for certain double headed products from people like Matrox) only one card can occupy the legacy ISA address area so extra cards never have their VGA BIOS' run at all.
Thanks, that is a *great* idea.
The thing is, the chip on the L440GX is a cirrus, and cirrus has always been pretty good about open specs on their chips. If it were one of the other companies I would think about giving up :-) I think we can get this. We'll be talking to the xfree guys.
Also, in a pinch I can survive in the cluster with serial console until we get this.
ron
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"Ronald G. Minnich" wrote:
On Fri, 18 Feb 2000, Todd Whitesel wrote:
Talk to the XFree86 4.0 guys; they're tackling the problem right now because they want to handle multi-headed machines, and (except for certain double headed products from people like Matrox) only one card can occupy the legacy ISA address area so extra cards never have their VGA BIOS' run at all.
Thanks, that is a *great* idea.
The thing is, the chip on the L440GX is a cirrus, and cirrus has always been pretty good about open specs on their chips. If it were one of the other companies I would think about giving up :-) I think we can get this. We'll be talking to the xfree guys.
I am an "XFree86 guy"
The current plan is to use BIOS-initialized VGA for the primary head, and vm86 mode (BIOS and BIOS calls!) to initialize the video BIOS of all secondary heads. If vm86 mode is not possible, then an X86 emulator, x86emu, does the job.
So, you need to run the video BIOS of the first head.
That's solution number one.
Solution number two: use framebuffer devices inside Linux kernel for video. "fbdev" is designed mainly for machines where no text graphics mode (e.g. vgacon) exists, but it can be used for any platform.
the thing is, as long as you depend on vga bios support, you're never going to be openbios. One reason is that graphics are increasingly a chip on the motherboard, with the vga bios in the motherboard nvram. There isn't room for linux and that vga bios in the nvram. Second is, until you get all the secrets out, we're locked in to braindead bios'es.
So we'll figure it out :-)
ron
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"Ronald G. Minnich" wrote:
the thing is, as long as you depend on vga bios support, you're never going to be openbios. One reason is that graphics are increasingly a chip on the motherboard, with the vga bios in the motherboard nvram. There isn't room for linux and that vga bios in the nvram. Second is, until you get all the secrets out, we're locked in to braindead bios'es.
I agree with you! :)
So we'll figure it out :-)
VGA is the standard, that is why it is popular. Linux text mode console works because VGA works on most PCs. Executing video BIOS is an absolute requirement to supporting VGA in a generic fashion.
WARNING: You are opening a huge can of worms if you ditch VGA and video BIOS. I think it is a good idea, but it is difficult to implement. I know, I've written graphics drivers.
If you do NOT want to support VGA in a generic fashion, then you MUST include specific support for each graphics chipset your users may have. Those are the only two options.
Some video cards include Open Firmware ROMs. This is the platform-independent way of initializing the video card. Open Firmware ROM code is somewhat like forth, from what I've heard.
For video cards without Open Firmware support, you need to get the video card datasheet and figure out how to initialize the card. You must do this for each model of each card. Sometimes initializing to text mode is easy, sometimes not.
This task is further complicated by the fact that _many_ video cards invest a lot of tech in their video BIOS's. BIOS stores critical undocumented RAM timing information and similar board details which differ from board to board, but not chip to chip. Usually you can get away with 100% conservative video settings, but this is not failsafe.
Once you have code to initialize popular video cards to a sane state, you can start using linuxbios on different computers...
As i said, ditching VGA and video BIOS is a very good thing. But it is also difficult to get right, and requires lots of additional code over the simply-support-VGA-the-old-way solution.
Choose well, grasshopper. :)
ah, such fun. Jeff, can you tell me more.
On Fri, 18 Feb 2000, Jeff Garzik wrote:
VGA is the standard, that is why it is popular. Linux text mode console works because VGA works on most PCs. Executing video BIOS is an absolute requirement to supporting VGA in a generic fashion.
Let's take the L440GX (please! :-). I want video on it to act like VGA.
On this board you've got to set some things in PCI config registers to enable 'VGA mode'. These are for such things are mapping of 0xa0000 space, MDA space, which out/in instructions go to the card, and so on.
My question to you: if I enable the address/IO bits to enable 'VGA', and then I do VGA-style commands to the card, will the card initialize or sit there and do nothing?
Is there really no way short of calling the video bios to init the card?
If it's true there's no other way, well, I'm not completely screwed for cluster use, but it's still bad for everyone else.
Next question then: what's the offset in video bios of the init routine, or how do you find it, and what's it expect? working stack? return address in bx? Does it walk the PCI bus to find itself, and then init itself? what should I expect?
If I can't init video from open source I'll put this one on the back burner for now and do it later. But we've got to deal with this at some point.
Also recall that there used to be similar arguments about things like disk and ethernet controllers. The decision in the open source community is to support what you can, and not try to do everything. People who really want you to support their card will come around eventually. Intel once made me sign a five-year NDA on the pro-100a network card; five months later they were giving the docs away to anyone willing to write a driver for *bsd or linux. They learned.
ron
p.s. true story: someone at a famous research lab once wrote a 386 simulator, just so he could figure out how to init a graphics card. He booted dos on his simulator and waited for the graphics card init to run, at which point he stopped worrying about his simulator :-) Took about a day or two, but he said it was worth it :-)
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"Ronald G. Minnich" wrote:
My question to you: if I enable the address/IO bits to enable 'VGA', and then I do VGA-style commands to the card, will the card initialize or sit there and do nothing?
Is there really no way short of calling the video bios to init the card?
Each video card has a _lot_ of knowledge stored in the video BIOS.
When a card is made, an OEM takes a video chip and sticks it on their board. The only way for the chip to know how to correctly access board memory, and other crucial details, are stored in the video BIOS.
The rule is: if you do not init video BIOS, then you must init the video on a per-chipset basis (ie. no generic VGA)
Next question then: what's the offset in video bios of the init routine, or how do you find it, and what's it expect? working stack? return address in bx? Does it walk the PCI bus to find itself, and then init itself? what should I expect?
Read the PCI spec on ROMs. Basically it can be an x86 code image, Open Firmware code image, or something else.
You will always have the problem of having to deal with x86 code images in expansion ROMs. Video BIOS is only one example.
why dont you have a look at the bocus ibm pc emulator, that boots an image of the elpin vga bios, see how bocus does it.
----- Original Message ----- From: Jeff Garzik jgarzik@mandrakesoft.com To: openbios@elvis.informatik.uni-freiburg.de Sent: Friday, February 18, 2000 1:39 PM Subject: Re: [OpenBIOS] Video
"Ronald G. Minnich" wrote:
My question to you: if I enable the address/IO bits to enable 'VGA', and then I do VGA-style commands to the card, will the card initialize or
sit
there and do nothing?
Is there really no way short of calling the video bios to init the card?
Each video card has a _lot_ of knowledge stored in the video BIOS.
When a card is made, an OEM takes a video chip and sticks it on their board. The only way for the chip to know how to correctly access board memory, and other crucial details, are stored in the video BIOS.
The rule is: if you do not init video BIOS, then you must init the video on a per-chipset basis (ie. no generic VGA)
Next question then: what's the offset in video bios of the init routine, or how do you find it, and what's it expect? working stack? return
address
in bx? Does it walk the PCI bus to find itself, and then init itself?
what
should I expect?
Read the PCI spec on ROMs. Basically it can be an x86 code image, Open Firmware code image, or something else.
You will always have the problem of having to deal with x86 code images in expansion ROMs. Video BIOS is only one example.
-- Jeff Garzik | The ultimate Windows 98 keyboard: Building 1024 | Ctrl, Alt + Del on one big key! MandrakeSoft, Inc. | - another cute fortune
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Edwin Rhodes wrote:
why dont you have a look at the bocus ibm pc emulator, that boots an image of the elpin vga bios, see how bocus does it.
As mentioned in a previous message, the XFree86 team uses 'x86emu' to boot a video BIOS on any system. Coder should look at that, it is being actively maintained across multiple platforms AFAIK.
hi is it posible to replace a 1 meg ibm pc flash bios chip with lets say a 2 meg or 4 meg or even 8 meg flash rom? or are we completely limited to 1 meg? edwin
----- Original Message ----- From: Ronald G. Minnich rminnich@lanl.gov To: openbios@elvis.informatik.uni-freiburg.de Sent: Friday, February 18, 2000 9:33 AM Subject: Re: [OpenBIOS] Video
the thing is, as long as you depend on vga bios support, you're never going to be openbios. One reason is that graphics are increasingly a chip on the motherboard, with the vga bios in the motherboard nvram. There isn't room for linux and that vga bios in the nvram. Second is, until you get all the secrets out, we're locked in to braindead bios'es.
So we'll figure it out :-)
ron
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On Fri, 18 Feb 2000, Edwin Rhodes wrote:
hi is it posible to replace a 1 meg ibm pc flash bios chip with lets say a 2 meg or 4 meg or even 8 meg flash rom? or are we completely limited to 1 meg? edwin
I think it is not practical. The flash is a surface-mount device, and there are not even the traces on the motherboard to connect higher density devices. We're stuck.
ron
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I know of a flash that can go in the unused ISA slot, the one shared with a PCI and taken. I think you can go upto Gigas. And it can even be changed on the fly ... ----- Original Message ----- From: "Ronald G. Minnich" rminnich@lanl.gov To: openbios@elvis.informatik.uni-freiburg.de Sent: Saturday, February 19, 00 2:06 AM Subject: Re: [OpenBIOS] Video
On Fri, 18 Feb 2000, Edwin Rhodes wrote:
hi is it posible to replace a 1 meg ibm pc flash bios chip with lets say
a 2
meg or 4 meg or even 8 meg flash rom? or are we completely limited to 1 meg? edwin
I think it is not practical. The flash is a surface-mount device, and there are not even the traces on the motherboard to connect higher density devices. We're stuck.
ron
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If we are going to be using a BIOS which is compatible with IEEE-1275 then we do not need to worry about VGA BIOS troubles, as the VGA BIOS will be machine independent FCode.
But it is not likely that Open Firmware video cards (and others for that matter) will appear over night.
-graham - To unsubscribe: send mail to majordomo@freiburg.linux.de with 'unsubscribe openbios' in the body of the message
Bob Dobbs wrote:
If we are going to be using a BIOS which is compatible with IEEE-1275 then we do not need to worry about VGA BIOS troubles, as the VGA BIOS will be machine independent FCode.
90% of all video BIOS are extremely ugly 16-bit and 32-bit-in-16-bit-mode hacks.
The other 10% are the above but include Open Firmware (for PPC mainly), or FCode as you describe.
not familiar with this, but does the integrated graphics chip appear as another PCI device?
On Fri, 18 Feb 2000, Ronald G. Minnich wrote:
the thing is, as long as you depend on vga bios support, you're never going to be openbios. One reason is that graphics are increasingly a chip on the motherboard, with the vga bios in the motherboard nvram. There isn't room for linux and that vga bios in the nvram. Second is, until you get all the secrets out, we're locked in to braindead bios'es.
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