MFC of r180753: ABI problems?

[John Baldwin]

On Saturday 23 August 2008 02:42:09 am M. Warner Losh wrote:
> In message: <200808212351.13464.max at love2party.net>
>
>             Max Laier <max at love2party.net> writes:
> : Hi,
> :
> : I'm wondering how to merge r180753 to stable/7 as luoqi@ has indicated
> : that he doesn't have time to take care of it right now.
> :
> : It seems that changing the size of pcicfgregs (aka struct pcicfg) which
> : is part of struct pci_devinfo is out of the question, right?  Ideas where
> : to store the HT related state or how to avoid storing the state are
> : welcome.
> :
> : The merge result is attached for reference.  This fix is essential for
> : many nforce based boards from ASUS which are rather common, I'm afraid. 
> : So it would be good to have this in 7.1/6.4, I think.
>
> I think this is OK.
>
> pcicfgregs is an internal to pci implementation detail.  You've added
> it at the end, so any leakage of the offsets won't matter.  All
> subclasses of pci would be affected.  Internal to the kernel isn't all
> that interesting, since they are all compiled at the same time.  This
> would only matter for modules.  Cardbus and acpi would be the only
> modules affected.  That would mean you couldn't boot a 7.0 kernel with
> a 7.1 set of modules or vice versa.  I'm not sure that is actually
> going to work anyway...

ACPI (and OFW's) PCI bus code isn't going to care, and I doubt cardbus is 
either.  Hmm, actually, cardbus doesn't, but ACPI actually does (acpi_pci 
uses its own extended ivars for PCI devices to cache ACPI handles).  That 
said, this particular ABI was actually broken earlier by MSI (though I didn't 
realize it at the time. :( ).

-- 
John Baldwin