Re: [RFC] asm-generic/pci_iomap.h: make custom PCI BAR requirements explicit
From: Luis R. Rodriguez
Date: Wed Sep 02 2015 - 21:45:16 EST
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@xxxxxxxx>
> > 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.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/