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    SubjectRe: [PATCH] iio: adc: Specify IOMEM dependency for adi-axi-adc driver
    On Wed, 1 Jul 2020 11:04:42 +0800
    David Gow <davidgow@google.com> wrote:

    > On Tue, Jun 30, 2020 at 6:07 PM Jonathan Cameron
    > <Jonathan.Cameron@huawei.com> wrote:
    > >
    > > On Tue, 30 Jun 2020 00:05:52 -0700
    > > David Gow <davidgow@google.com> wrote:
    > >
    > > > The Analog Devices AXI ADC driver uses the devm_ioremap_resource
    > > > function, but does not specify a dependency on IOMEM in Kconfig. This
    > > > causes a build failure on architectures without IOMEM, for example, UML
    > > > (notably with make allyesconfig).
    > > >
    > > > Fix this by making CONFIG_ADI_AXI_ADC depend on CONFIG_IOMEM.
    > > >
    > > > Signed-off-by: David Gow <davidgow@google.com>
    > > Hi David,
    > >
    > > Could you confirm what the build error is? I thought the stubs added in
    > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1bcbfbfdeb
    > > were meant to allow us to avoid having lots of depends on IOMEM lines for the
    > > few architectures who don't support it.
    >
    > No worries:
    > /usr/bin/ld: drivers/iio/adc/adi-axi-adc.o: in function `adi_axi_adc_probe':
    > torvalds-linux/drivers/iio/adc/adi-axi-adc.c:415: undefined reference
    > to `devm_platform_ioremap_resource'
    >
    > Alas, the devm_platform_ioremap_resource function isn't handled by the
    > UML stubs: it all seems to be in drivers/base/platform.c and
    > lib/devres.c, behind #ifdef HAS_IOMEM.
    >
    > In any case, improving IOMEM support for UML (at least for the KUnit
    > test case, which is my use case) is something I'd like to do. There
    > are only three drivers[1,2] upstream at the moment which fail to build
    > as-is, though, so it seemed worth trying to fix them in the meantime.
    > That being said, I tried just getting rid of the few #ifdef HAS_IOMEMs
    > around the various devm_*_ioremap functions, and everything seems to
    > be working... So maybe that's a false dependency given the various
    > stubs (at least on UML). I used this (hideously hacky) patch:
    >
    > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
    > index c0d0a5490ac6..b6f08c88e2b6 100644
    > --- a/drivers/base/platform.c
    > +++ b/drivers/base/platform.c
    > @@ -61,7 +61,7 @@ struct resource *platform_get_resource(struct
    > platform_device *dev,
    > }
    > EXPORT_SYMBOL_GPL(platform_get_resource);
    >
    > -#ifdef CONFIG_HAS_IOMEM
    > +#if 1//def CONFIG_HAS_IOMEM
    > /**
    > * devm_platform_get_and_ioremap_resource - call devm_ioremap_resource() for a
    > * platform device and get resource
    > diff --git a/lib/Makefile b/lib/Makefile
    > index b1c42c10073b..35c21af33b93 100644
    > --- a/lib/Makefile
    > +++ b/lib/Makefile
    > @@ -115,7 +115,7 @@ obj-y += math/ crypto/
    >
    > obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
    > obj-$(CONFIG_GENERIC_PCI_IOMAP) += pci_iomap.o
    > -obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o
    > +obj-y += iomap_copy.o devres.o
    > obj-$(CONFIG_CHECK_SIGNATURE) += check_signature.o
    > obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
    >
    > ---
    >
    > If this seems to work more broadly, I may try to clean it up and post
    > it for broader review.

    Looks like a good approach to me!

    Jonathan

    >
    > Cheers,
    > -- David


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