On 5/24/06, Matthew Garrett <[email protected]> wrote:
On Tue, May 23, 2006 at 07:38:40PM -0400, Jon Smirl wrote:
> 2) The ROM support in the kernel knows about the shadow RAM copy at
> C000::0. When you request the ROM from a laptop video system it
> returns a map to the shadow RAM copy, not to a physical ROM. You need
> access to the shadow RAM copy to get to things the BIOS left there
> when it ran.
My experience is that, on some laptops, the code at c000:0003 may jump
into some other address block that isn't necessarily shadowed. There's
no reason to assume that POSTing an ancilliary ROM will work after the
system has left the BIOS. Further, my laptop doesn't appear to have a
rom entry in sysfs, which makes getting at stuff that way rather more
awkward...
As outlined in the previous mail, you don't repost a primary adapter
that has already been posted. Adapters should only get posted once.
Laptop adapters are always primary. However, you may need access to
the shadow ROM copy to get info out of it and to run non-post
functions.
A missing sysfs ROM entry is probably a bug. There is a quirk in
arch/i386 that detects shadow video ROMs and tracks the primary video
adapter. It probably needs some special case code added for your
chipset. You're the first report of it being missing. Since I don't
have your laptop you'll need to debug this yourself. It shouldn't be
hard, it is a tiny piece of code.
The ROM attribute feature is not well tested on all platforms since
not much of the user space code that should be using it hasn't been
changed yet.
--
Jon Smirl
[email protected]
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