Groups > linux.kernel > #1672043

Re: [PATCH v2] um: add dummy ioremap and iounmap functions

From	Logan Gunthorpe <logang@deltatee.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] um: add dummy ioremap and iounmap functions
Date	2017-06-21 23:30 +0200
Message-ID	<tUVmi-3od-13@gated-at.bofh.it> (permalink)
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Poke.

On 08/06/17 01:17 PM, Richard Weinberger wrote:
> Am 08.06.2017 um 20:53 schrieb Logan Gunthorpe:
> IMHO an ifdef in scatterlist code does not hurt.
> It is equally ugly than mocking ioremap for UML.

I disagree. Having ifdefs scattered around all call sites of a function
is *much* worse than having an extra mock function tucked away in a
header file somewhere.

It's a very common pattern in the kernel for providers of functions that
depend on a configuration option to provide mock functions when the
configuration option is not selected. This prevents needing every caller
of said function to put #ifdefs around the call. For a few examples:

include/linux/blkdev.h:1952
include/linux/dax.h:24
include/linux/pci.h:1329

And, frankly, it's _exactly_ what Linus Torvalds himself was arguing
against in the link I sent up-thread [1].

> So, I'm puzzled.
> Arnd, what do you think?
> Shall !HAS_IOMEM archs just mock these functions?

So, once again, 'um' is now the only architecture that has this problem
since tile and s390 accepted my patches (and without a fuss too). So can
you please consider merging this patch or proposing something that will
also fix the problem?

Thanks,

Logan

[1] http://yarchive.net/comp/linux/ifdefs.html

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Re: [PATCH v2] um: add dummy ioremap and iounmap functions Logan Gunthorpe <logang@deltatee.com> - 2017-06-21 23:30 +0200
  Re: [PATCH v2] um: add dummy ioremap and iounmap functions Arnd Bergmann <arnd@arndb.de> - 2017-06-21 23:40 +0200
  Re: [PATCH v2] um: add dummy ioremap and iounmap functions Logan Gunthorpe <logang@deltatee.com> - 2017-06-21 23:40 +0200
  Re: [PATCH v2] um: add dummy ioremap and iounmap functions Richard Weinberger <richard@nod.at> - 2017-06-21 23:40 +0200

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