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

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Date:   Mon, 9 Apr 2018 20:02:47 -0500
From:   Rob Herring <robh@...nel.org>
To:     Dan Williams <dan.j.williams@...el.com>
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 4:05 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> 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.

You mean the stuff reviewed last week in the middle of the merge
window? Sounds like 4.18 material to me.

Rob