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SubjectRe: [PATCH 0/4] PCI legacy I/O port free driver (take4)
On Thu, Mar 02, 2006 at 10:24:36AM -0700, Grant Grundler wrote:
> On Thu, Mar 02, 2006 at 03:50:57PM +0000, Russell King wrote:
> > I've been wondering whether this "no_ioport" flag is the correct approach,
> > or whether it's adding to complexity when it isn't really required.
> I think it's the simplest solution to allowing a driver
> to indicate which resources it wants to use. It solves
> the problem of I/O Port resource allocation sufficiently
> well.

I have another question (brought up by someone working on a series of
ARM machines which make heavy use of MMIO.)

Why isn't pci_enable_device_bars() sufficient - why do we have to
have another interface to say "we don't want BARs XXX" ?

Let's say that we have a device driver which does this sequence (with,
of course, error checking):

pci_enable_device_bars(dev, 1<<1);

(a) should PCI remember that only BAR 1 has been requested to be enabled,
and as such shouldn't pci_request_regions() ignore BAR 0?

(b) should the PCI driver pass into pci_request_regions() (or even
pci_request_regions_bars()) a bitmask of the BARs it wants to have
requested, and similarly for pci_release_regions().

Basically, if BAR0 hasn't been enabled, has pci_request_regions() got
any business requesting it from the resource tree?

Russell King
Linux kernel 2.6 ARM Linux -
maintainer of: 2.6 Serial core
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