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Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements explicit

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On Sat, Aug 29, 2015 at 08:25:05AM -0700, Christoph Hellwig wrote:
> On Fri, Aug 28, 2015 at 05:17:27PM -0700, Luis R. Rodriguez wrote:
> > From: "Luis R. Rodriguez" <mcgrof@suse.com>
> > 
> > The S390 architecture requires a custom pci_iomap() implementation
> > as the asm-generic implementation assumes there are disjunctions
> > between PCI BARs, and on S390 PCI BAR are not disjunctive, S390 requires
> > the bar parameter in order to find the corresponding device and create
> > the mapping cookie.
> > 
> > This clash with the asm-generic pci_iomap() implementation is implicit,
> > there are no current semantics to make this incompatability explicit.
> > Make the S390 PCI BAR non-disjunction incompatibility explicit, and
> > also pave the way for alternative incompatibilities to be defined.
> > 
> > While at it, as with the ioremap*() variants, since we have no clear
> > semantics yet well defined provide a solution for them that returns
> > NULL. This allows architectures to move forward by defining pci_ioremap*()
> > variants without requiring immediate changes to all architectures. Each
> > architecture then can implement their own solution as needed and
> > when they get to it.
> 
> Now that you have the config symbol available why not move the S390
> implementation to generic code based on that can kill of
> asm/pci_iomap.h?  Seems like we're really not dealing with something
> inherent to the architecture, but two possible implementations based
> on architecture constraints.

That would be the other approach to take too, but perhaps that can wait
until yet another architecture with similar requirement pops up.

 Luis
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[RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements explicit "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-29 02:20 +0200
  Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements  explicit Randy Dunlap <rdunlap@infradead.org> - 2015-08-29 04:20 +0200
  Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements  explicit Christoph Hellwig <hch@infradead.org> - 2015-08-29 17:30 +0200
    Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements  explicit "Luis R. Rodriguez" <mcgrof@suse.com> - 2015-09-03 03:50 +0200
  Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements explicit Arnd Bergmann <arnd@arndb.de> - 2015-08-30 21:40 +0200
    Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements  explicit "Luis R. Rodriguez" <mcgrof@suse.com> - 2015-09-03 03:50 +0200
      Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements explicit "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-09-03 03:50 +0200

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