[PATCH v7 1/6] pci: Introduce pci_register_io_range() helper function.

Bjorn Helgaas
2014-04-08T16:54:01Z

On Tue, Apr 8, 2014 at 4:22 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 08 April 2014 10:50:39 Liviu Dudau wrote:
>> On Mon, Apr 07, 2014 at 06:58:24PM +0100, Bjorn Helgaas wrote:
>> > On Mon, Apr 7, 2014 at 5:36 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>> >
>> > > I think migrating other architectures to use the same code should be
>> > > a separate effort from adding a generic implementation that can be
>> > > used by arm64. It's probably a good idea to have patches to convert
>> > > arm32 and/or microblaze.
>> >
>> > Let me reiterate that I am 100% in favor of replacing arch-specific
>> > code with more generic implementations.
>> >
>> > However, I am not 100% in favor of doing it as separate efforts
>> > (although maybe I could be convinced). The reasons I hesitate are
>> > that (1) if only one architecture uses a new "generic" implementation,
>> > we really don't know whether it is generic enough, (2) until I see the
>> > patches to convert other architectures, I have to assume that I'm the
>> > one who will write them, and (3) as soon as we add the code to
>> > drivers/pci, it becomes partly my headache to maintain it, even if
>> > only one arch benefits from it.
>
> Fair enough.
>
> My approach to the asm-generic infrastruction has mostly been to ensure
> that whoever adds a new architecture has to make things easier for the
> next person.

That's a good rule. But if we add a generic implementation used only
by one architecture, the overall complexity has increased (we added
new unshared code), so the next person has to look at N+1 existing
implementations. If we even convert one existing arch, that seems
like an improvement: we have N implementations with one being used by
at least two arches.

Bjorn