Re: [RFC] I/O Access Abstractions

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> For example, one board I've got doesn't allow you to do a straight
> memory-mapped I/O access to your PCI device directly, but have to reposition a
> window in the CPU's memory space over part of the PCI memory space first, and
> then hold a spinlock whilst you do it.

What does this prove. PA-RISC has this problem in reverse for I/O cycle access
to PCI slots on hppa1.1 at least. Cookies work _fine_

And by the time you are taking a spinlock who cares about the add, you can do
that while the bus transactions for the atomic op are completing

On the other hand each call, each push of resource * pointers costs real clocks
on x86