PMode and VESA

[gedeon]

Hello
I started programming my OS few month ago.
And i have now a lot of documentation.
But one question still have no answer
How to programming VESA mode in protected Mode ?
I know how to do that in real mode (int 10 ...), but i have no found documentation for the pmode.
Does anibody have an answer ? or documentation ?

[Jeroen Jacobs]

well... there are two possible solutions :

- Switch to VM86 mode for each vesa-call (not good)
- VESA 2.0 has a 32 bit interface (I think it uses far calls). Search Google for VESA 2.0 . It's very well documented.

Jeroen Jacobs

[gedeon]

Thank you JJ

It's already done
easiest than google
www.vesa.org
good documentation

Ps : 1st solution, agree with you , very very bad solution beurk!

[Pype.Clicker]

now, VBE 3.0 is out and supports a full 32 bits API (even for modes enumerating, switching, etc. which had to be done with VM86 with older VBEs)

Oh, by the way, i'm looking for a C implementation of this for my kernel, so if you don't already have a kernel but are already working on the video driver in PMODE, you're my friend

[gedeon]

Thank you i have VBE 3 .0 Documentation.
Sorry but I have a kernel , and for the moment working with VBE mode is not possible with Bochs (maybe it's wrong with 1.4 version), so my OS is in VGA 16 mode.
I work on a website with documentation for my OS and soon it will be online ( i hope), and when my VBE mode driver will be ready , email me and get the source with some explanations.

[K.J.]

Is VBE 3 supported by many graphics cards?

K.J.

[Chris Giese]

The protected mode functions supported by VESA 2.x don't
seem very useful. Example: protected-mode bank-switch.
If VESA 2.x has a linear framebuffer, why do you need this?

I could be mistaken, but I thought the VESA 3.x functions
run in 16-bit protected mode.

[Pype.Clicker]

I could be mistaken, but I thought the VESA 3.x functions
run in 16-bit protected mode.

As far as i remember, yes: you have to jump to a 16-bits code segment, but this is still pmode working, and thus it's really cheaper to implement than if it was in realmode ... It's just a trick bios developers found so that the very same code can be run in both real & protected mode by just changing what differs: segments value (usually, 0xc000 is hardcoded, now you can select 0x28 instead

Actually, i've found VBE 3.0 is present on my GeForce 2, so i guess you can expect it on - say - all video card from Y2K ...