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Date:   Fri, 6 May 2022 14:16:56 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@orcam.me.uk>
To:     Arnd Bergmann <arnd@kernel.org>
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Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select
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On Fri, 6 May 2022, Arnd Bergmann wrote:

> >  So what happens if the instruction is given an I/O rather than memory BAR
> > as the relevant argument?  Is the address space indicator bit (bit #0)
> > simply ignored or what?
> 
> Not sure. My best guess is that it would actually work as you'd expect,
> but is deliberately left out of the architecture specification so they don't
> have to to validate the correctness.  Note that only a small number of
> PCIe cards are actually supported by IBM, and I think the firmware
> only passes devices to the OS if they are whitelisted.

 That makes sense, thanks!

  Maciej