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From:   Brendan Higgins <brendanhiggins@google.com>
Date:   Tue, 21 Jul 2020 16:55:06 -0700
Message-ID: <CAFd5g46ughJzQCH_mh897NYovVuryvM1_Xi-9YfP6nsUHZsT4g@mail.gmail.com>
Subject: Re: [RFC PATCH] platform: ioremap: Build iomap functions even without HAS_IOMEM
To:     David Gow <davidgow@google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jeff Dike <jdike@addtoit.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Logan Gunthorpe <logang@deltatee.com>,
        Richard Weinberger <richard@nod.at>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        KUnit Development <kunit-dev@googlegroups.com>,
        linux-um <linux-um@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, Jul 20, 2020 at 10:45 PM David Gow <davidgow@google.com> wrote:
>
> A number of drivers use devm_platform_ioremap_resource(), but do not (or
> did not) explicitly depend on IOMEM[1,2]. Given that the only platform
> without HAS_IOMEM seems to be UML, and it has sufficient stubs for
> devm_platform_ioremap_resource() and its dependencies to build, we can
> remove the HAS_IOMEM requirement here, rather than playing whack-a-mole
> with different drivers which don't try to build against ARCH=um.
>
> The reason this works at the moment is that stub ioremap and iounmap
> functions were added to UML to support this sort-of thing[3]. This
> particular change doesn't require adding any additional stubs, but there
> is possibly room in the future to stub out the remaining iomem functions
> (or to provide mock implementations for testing), and get rid of
> HAS_IOMEM entirely.
>
> [1]: https://lkml.org/lkml/2020/6/30/176
> [2]:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1e7468bd9d30a21e059af477106dc5588ae52dff
> [3]:
> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1405627.html
>
> Signed-off-by: David Gow <davidgow@google.com>

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>