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Date:   Fri, 22 Jul 2022 23:41:54 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@orcam.me.uk>
To:     Rob Herring <robh@kernel.org>
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Subject: Re: [PATCH v3 2/2] asm-generic: Add new pci.h and use it
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On Fri, 22 Jul 2022, Rob Herring wrote:

> P.S. I really wish I/O space would disappear completely.

 Some systems make it happen already, such as the POWER9 platform and its 
PHB4 host bridge (which doesn't handle PCIe TLP I/O read or write commands 
at all), however some PCI/e devices do require I/O space, such as IEEE 
1284 parallel port adapters.  Some PCI devices dating back as far as to 
1990s provide dual mapping of their resources via an I/O and a memory BAR 
both at a time, so we can choose which to use depending on circumstances.

 FWIW,

  Maciej