Re: [PATCH] add PCI ROMs to sysfs

[Jon Smirl <jonsmirl@yahoo.com>]

--- Martin Mares <mj@ucw.cz> wrote:
> I was thinking again about the VGA ROM's and I tend to believe that
> even if you happen to guess correctly where is the ROM shadowed, it
> would be better to show the _original_ ROM image and deliver the
> shadow copy as a separate file. (If somebody decides to initialize 
> the VGA manually by running the code in the ROM, is the shadow copy
> any better?)

The shadowing logic is a must have for laptops. BenH and I discovered
this the hard way. Some laptops take the system and video ROM images,
combine them and then compress them into a ROM. At boot time these ROM
images are decompressed into RAM at C0000 and F0000. For these system
the only place to get the ROM data for things like video timings is
from the shadow area. Putting the shadow logic into the shared ROM code
lets up remove it from all of the video drivers. This lets us write
video drivers that don't care if the card is primary or secondary.

Video cards that are using the shadow copy don't need to be initially
reset. Since they are your boot display the system BIOS must have
already initialized them. Instead the you need the shadow image since
it may contain the timing data needed to change modes on a laptop display.

=====
Jon Smirl
jonsmirl@yahoo.com


		
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