[PATCH] New frame buffer detection algorithm and loadrom command for efi platform

[Bean]

Hi,

This patch improves the frame buffer detection algorithm. It uses pci
to find the video memory base, then scan it for frame buffer.

It also add a loadrom command which can be used to enable accel
graphic driver. The idea is that you can grab the video bios dump, and
optionally the IVT from pc mode, then load them in efi.

To grab bios dump:
sudo dd if=/dev/mem of=bios.bin bs=65536 skip=12 count=1

You can also include the system bios by changing the count to 4.

To grab IVT dump:
sudo dd if=/dev/mem of=ivt.bin bs=1024 count=1

Then, to load them in grub-efi (ivt.bin is optionally):
loadrom /bios.bin /ivt.bin

Here are some of the findings concerning different video cards:

Old 32-bit efi model, intel card:
Works with intel driver, no need to load vbios or ivt.

New 64-bit efi model, intel card:
Works with intel driver, needs to load vbios.

New 64-bit efi model, nvidia card:
Works with nvidia driver, no needs to load vbios or ivt. However, the
backlight value is set too low so desktop is barely visible. You need
to use a small tool to adjust backlight. The nv driver doesn't work.

New 64-bit efi model, ati radeon card:
Works with fglrx driver, needs to load vbios and ivt. The radeonhd
driver doesn't work.

-- 
Bean

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