linux-kernel - Re: [PATCH v8 3/9] pci: Introduce pci_register_io

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Date:	Wed, 9 Jul 2014 09:21:17 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Liviu Dudau <Liviu.Dudau@....com>,
	linux-pci <linux-pci@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 3/9] pci: Introduce pci_register_io_range() helper function.

On Wed, Jul 9, 2014 at 12:20 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Tuesday 08 July 2014, Bjorn Helgaas wrote:

>> I think my confusion is because your pci_register_io_range() and
>> pci_addess_to_pci() implementations assume that every io_range starts at
>> I/O port 0 on PCI (correct me if I'm wrong).  I suspect that's why you
>> don't save the I/O port number in struct io_range.
>
> I think you are just misreading the code, but I agree it's hard to
> understand and I made the same mistake in my initial reply to the
> first version.
>
> pci_register_io_range and pci_address_to_pci only worry about the mapping
> between CPU physical and Linux I/O address, they do not care which PCI
> port numbers are behind that. The mapping between PCI port numbers and
> Linux port numbers is done correctly in patch 8/9 in the
> pci_host_bridge_of_get_ranges() function.

Ah, I see now.  Thanks for explaining this again (I see you explained
it earlier; I just didn't understand it).  Now that I see it, it *is*
very slick to handle both MMIO and PIO spaces the same way.

Bjorn
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