[coreboot] [SeaBIOS] One ROM for multiple devices

Marc Jones marcj303 at gmail.com
Wed Jun 13 19:37:50 CEST 2012

On Wed, Jun 13, 2012 at 12:50 AM, Gerd Hoffmann <kraxel at redhat.com> wrote:
> On 06/13/12 01:06, Steve Goodrich wrote:
>> Please be aware that this is cross-posted to both the SeaBIOS and coreboot
>> mailing lists.  I know this is generally frowned upon, but I believe the
>> subject is valid for discussion in both forums.
>> I have a coreboot/SeaBIOS image containing an option ROM that works for
>> multiple graphics devices (seven or eight of them).  These graphics devices
>> come from the same vendor but each device has its own (unique) PCI Device
>> ID.  If I'm going to load the driver from SeaBIOS, I need to have a copy of
>> the option ROM file, each with the name of the target PCI device (e.g.
>> "pci1234,5678.rom").  Having seven or eight copies in the BIOS image file is
>> a waste of space.
>> Stefan R. submitted a solution to coreboot to enable mapping one ROM's
>> vendor/device ID to another and this solution has worked well for
>> coreboot-centric uses.
>> Unfortunately, this does not address the problem in SeaBIOS.  I have started
>> working on a solution that extends what Stefan has done, but moves the data
>> into a single "translate" file in CBFS.  This file contains simple data to
>> allow coreboot and/or SeaBIOS to take a PCI device's vendor/device info and
>> retrieve alternate vendor/device values.
>> Since both coreboot and SeaBIOS understand CBFS, the basic translation code
>> would be identical.
>> The data file consists of sets of four 16-bit binary values:
>>     u16 vendor1, device1; // translate FROM this PCI v/d
>>     u16 vendor2, device2; // translate TO this PCI v/d
> Another possible solution would be to add support for symbolic links to
> cbfs.
> How do you get around the limitation of a single pci id in the rom
> header?  Or does seabios skip the pci id verification for rom files
> loaded from cbfs?

This is why I think it should not be part of cbfs, The problem is not
a file handling issue. It is a function of the PCI ROM handling that
has a special case for onboard ROMs. The PCI rom routine needs to
understand that it is using a compatible ID and skip the ROM header
checking (Seabios doesn't check but coreboot does). VGA ROMs are the
most common case, but happens with ethernet and ahci/raid ROMs as



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