linux-kernel - Re: [PATCH] drivers/of: Introduce ARCH_HAS_OWN_OF

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Date:   Mon, 9 Apr 2018 14:05:20 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Rob Herring <robh@...nel.org>
Cc:     "Oliver O'Halloran" <oohall@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Device Tree <devicetree@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        sparclinux@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] drivers/of: Introduce ARCH_HAS_OWN_OF_NUMA

On Mon, Apr 9, 2018 at 1:52 PM, Rob Herring <robh@...nel.org> wrote:
> On Mon, Apr 9, 2018 at 2:46 AM, Oliver O'Halloran <oohall@...il.com> wrote:
>> Some OF platforms (pseries and some SPARC systems) has their own
>> implementations of NUMA affinity detection rather than using the generic
>> OF_NUMA driver, which mainly exists for arm64. For other platforms one
>> of two fallbacks provided by the base OF driver are used depending on
>> CONFIG_NUMA.
>>
>> In the CONFIG_NUMA=n case the fallback is an inline function in of.h.
>> In the =y case the fallback is a real function which is defined as a
>> weak symbol so that it may be overwritten by the architecture if desired.
>>
>> The problem with this arrangement is that the real implementations all
>> export of_node_to_nid(). Unfortunately it's not possible to export the
>> fallback since it would clash with the non-weak version. As a result
>> we get build failures when:
>>
>> a) CONFIG_NUMA=y && CONFIG_OF=y, and
>> b) The platform doesn't implement of_node_to_nid(), and
>> c) A module uses of_node_to_nid()
>>
>> Given b) will be true for most platforms this is fairly easy to hit
>> and has been observed on ia64 and x86.
>
> How specifically do we hit this? The only module I see using
> of_node_to_nid in mainline is Cell EDAC driver.

The of_pmem driver is using it currently pending for a 4.17 pull
request. Stephen hit the compile failure in -next.