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Re: [PATCH] New x86_64 EFI patch

From: Bean
Subject: Re: [PATCH] New x86_64 EFI patch
Date: Sat, 12 Jul 2008 23:48:18 +0800

On Sat, Jul 12, 2008 at 11:37 PM, Bean <address@hidden> wrote:
> On Sat, Jul 12, 2008 at 11:26 PM, Robert Millan <address@hidden> wrote:
>> On Sat, Jul 12, 2008 at 11:16:31PM +0800, Bean wrote:
>>> On Sat, Jul 12, 2008 at 10:41 PM, Robert Millan <address@hidden> wrote:
>>> > On Wed, Jul 09, 2008 at 12:31:53AM +0800, Bean wrote:
>>> >> > -- I tried passing video=intelfb to linux; it worked under grub2-pc but
>>> >> > didn't improve anything under efi.
>>> >>
>>> >> intelfb doesn't work. The only way to see console in efi is to use
>>> >> video=vesafb or video=efifb.
>>> >
>>> > How come?  I thought intelfb used the bare hardware.
>>> The video register in efi mode is not setup in the same way as bios.
>>> There are two sets of register. In EFI, set A is completely zero,
>>> while set B have non-zero value. But in bios mode, both set have
>>> non-zero value. I guess this is because bios have text and graphic
>>> mode, while efi only have graphic mode. (text mode in efi is emulated)
>> But isn't intelfb supposed to access the hardware without any support
>> from bios/vesa or efi?
> Intelfb uses the environment setup before, it doesn't try to
> reinitialize video registers.


I think the real problem of intelfb is that it uses agp, which
requires video hardware to be configure properly. But if we use vesafb
or efifb, it uses the frame buffer, so as long as we setup video
information properly in grub2, we can see console output.


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