[coreboot] CBFS transition plan

Kevin O'Connor kevin at koconnor.net
Wed May 6 02:44:59 CEST 2009

On Tue, May 05, 2009 at 09:13:32AM -0600, Myles Watson wrote:
> 3. PCI ROM optimization.  There should be some optimization for ROMs.
>     a. Possibilities:
>         1. Traverse ROM once and set a flag in devices which have ROMs
>         2. Traverse ROM and keep a list of ROMs
>         3. ....

Are you referring to the email I sent on the time SeaBIOS spent
traversing CBFS to find option roms?

I did modify SeaBIOS so that option roms scans are much faster.  (The
cost is now negligible.)  I accomplished this by ending the file scan
if a signature of zeros is found.

I don't think caching the list of files in the flash will work well -
even one brute force scan will take too much time on large flash
chips.  Instead, I think CBFS needs to have an orderly layout of files
which doesn't require users to do a brute force scan.

I think there's a simple way to accomplish this - have cbfstool create
"null" files that contain all the empty space.  Then the users of cbfs
(eg, coreboot, seabios) wouldn't need any special code - they would
skip them just like they skip over any other file.


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