[coreboot] VGA and Graphics

[ron minnich]

Igor, if you are going to say things like "AFAIK there is no public
description of these tables' layout and contents, only Intel knows how to
build and parse them.", it's really a good idea to back it up with a
primary source, especially since you also use phrases like "I assume" and
"I guess". I am pretty sure you're wrong in this case. The V in VBT, as I
understand it, means VESA, and VESA has been a standard for about 30 years.

Please, everyone, if you're going to move this conversation forward, you
need to cite primary sources at least, such as this one:
http://www.petesqbsite.com/sections/tutorials/tuts/vbe3.pdf.


thanks

ron

On Tue, Apr 4, 2017 at 10:19 AM Igor Skochinsky via coreboot <
coreboot at coreboot.org> wrote:

> Hello Zoran,
>
>
> Monday, April 3, 2017, 8:58:43 PM, you wrote:
>
>
>
> VBT should fulfill this VBE standard, as my best understanding is, or not?!
>
> VBE only describes the int 10h BIOS interface extensions, VBT are tables
> used by Intel to provide info about how to control the GPU (I assume).
> AFAIK there is no public description of these tables' layout and contents,
> only Intel knows how to build and parse them.
> Both VBE(code) and VBT (data) may be present in the video card's option
> ROM, I guess that's the only common part.
>
>
>
>
> Zoran
>
> On Mon, Apr 3, 2017 at 7:36 PM, Igor Skochinsky via coreboot <
> coreboot at coreboot.org> wrote:
> Hello Zoran,
>
> Monday, April 3, 2017, 9:24:41 AM, you wrote:
>
>
> > *VBT is not code, it's a table* -- that's what the T is -- and you can
> create it any way you want.
>
> Not going to say more, anyway. Just to point to the standard:
> https://en.wikipedia.org/wiki/
> <https://en.wikipedia.org/wiki/VESA_BIOS_Extensions>VESA_BIOS_Extensions
> <https://en.wikipedia.org/wiki/VESA_BIOS_Extensions>
>
>
> Not sure why you posted this link. VBE is not VBT, it's a completely
> separate and different thing.
>
>
>
>
>
> To clever enough! ;-)
>
> Zoran
>
> On Mon, Apr 3, 2017 at 2:38 AM, ron minnich <rminnich at gmail.com> wrote:
> As for graphics startup, here's what I learned when I was doing this in
> 2012/2013: the kernel could start sandy and ivy with no vbios needed.
> However, I have been told that the veil of secrecy has started to draw a
> bit closer in subsequent chipsets, and that something like a VGA BIOS/GOP
> has to run or graphics will not work. I really don't know, I have not
> looked at this in over 3 years.
>
> Todd, just to make sure we're on the same page, VBT is not code, it's a
> table -- that's what the T is -- and you can create it any way you want.
>
> Also, as for numbers: the fastest graphics startup, by far, was when we
> had coreboot- based startup with configuration specialized to the chromeos
> laptop. How fast? At one point we had a pixel booting to chromeos prompt in
> 2.7 seconds, reduced from 7.7 seconds when linux did the graphics init.
> We've seen that the linux graphics init is highly concurrent and
> generalized, and that tends to mean slow. Of course this was all far faster
> than the 8086-mode vga BIOS supplied by "the vendor". But we were a bit
> surprised to see how much faster coreboot was than the linux kernel.
>
> I doubt this speed difference matters any more, since boot time only needs
> to be "fast enough" nowadays and 10 seconds seems to do it for most people
> -- plus, any 5-second advantage in boot time vanishes as soon as you go to
> your first web page.
>
> ron
>
>
>
> On Sun, Apr 2, 2017 at 5:31 PM ron minnich <rminnich at gmail.com> wrote:
> So, I'll mention go userland one last time, for a simple reason: I have it
> on good authority that at some places, saying you have a go userland
> instead of a c userland checks a check box on a security checklist. I think
> that's a sensible decision, having watched all the awful ways that C
> programs tend to go wrong :-)
>
> ron
>
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> *--  WBR,  Igor *--
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