Re: arch/x86/Kconfig selects invalid HAVE_READQ, HAVE_WRITEQ vars

[Robert Hancock]

Roland Dreier wrote:
>  > Also, atomicity might not be possible to guarantee on the bus level: 
>  > say the device sits on a 32-bit PCI bus. (No matter what instruction 
>  > the CPU gets, a readq/writeq there has to be done as two 32-bit bus 
>  > accesses.)
>
> Well, the conventional PCI devices I know of with 64-bit registers were
> PCI-X cards, keyed so they would only fit into a 64-bit slot.  And of
> course there is no such thing as 32-bit PCI Express.

It's quite possible to use most 64-bit PCI-X cards in a 32-bit slot, 
with the 64-bit part of the card not plugged into anything. It's 
supposed to work (as long as the card can handle the voltage the slot uses).
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