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List:       linuxbios
Subject:    Re: [coreboot] APM and VESA
From:       Marc Jones <marcj303 () gmail ! com>
Date:       2011-05-31 16:50:15
Message-ID: BANLkTik_k8=2vXekKpYU=UzVeagfA=eLEA () mail ! gmail ! com
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On Sun, May 29, 2011 at 1:55 PM,  <cinap_lenrek@gmx.de> wrote:
> Hi,
>
> working on a bootloader, we added apm initialization code to the bootloader
> so the kernel doesnt have to switch to realmode and can just do 32 protected
> mode calls.
>
> the bootloader does the following things in realmode before starting the kernel:
>
> 1) do apm installation check (INT 0x15, AX=0x5300)
> 2) do apm disconnect (INT 0x15, AX=0x5304)
> 3) do apm connect to 32bit protected mode interface (INT 0x15, AX=0x5303, BX=0)
> 4) save and pass the register contents after the connect call in some form to the kernel
>
> but doing this seems to disable VESA bios functionality on some machines (via epia
> and p3-sbc) (INT 0x10, AX=0x4F00 doesnt return any modes)
>
> i dont have the machines where this happens and i dont know the exact return
> conditions of the vbe calls yet, but i plan to debug this using our realmode emulator
> but it might take us some time...
>
> my question is are we on the right track? is it possible that doing these APM
> calls disables VBE?
>
> --
> cinap
>

Hi cinap,

It sounds like you may have an interrupt vector chaining problem or
register corruption problem in you interrupt installation.

Marc


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