Re: linux-next: build failure after merge of the nvdimm tree

On Mon, Apr 9, 2018 at 12:34 AM, Oliver [off-list ref] wrote:

On Mon, Apr 9, 2018 at 1:38 PM, Oliver [off-list ref] wrote:

quoted

On Mon, Apr 9, 2018 at 1:16 PM, Stephen Rothwell [off-list ref] wrote:

quoted

Hi Dan,

After merging the nvdimm tree, today's linux-next build (x86_64
allmodconfig) failed like this:

ERROR: "of_node_to_nid" [drivers/nvdimm/of_pmem.ko] undefined!

Caused by commit

  717197608952 ("libnvdimm: Add device-tree based driver")

X86 seems to not have a version of of_node_to_nid() even though CONFIG_OF
and CONFIG_NUMA are both 'y' in this build.

It's a side effect of a driver selecting CONFIG_OF accidently. There's
a patch to fix this in the drm-misc-next tree:

https://lkml.org/lkml/2018/4/3/17

quoted

I have used the nvdimm tree from next-20180406 for today.

That works too.

Hmm, on closer inspection this is actually a bug in the of driver. The
patch above fixes the specific problem that we hit on ia64 due to
CONFIG_OF being selected by accident, but the underlying issue will
affect any platform that doesn't provide an implementation of
of_node_to_nid().

The fundamental problem is that the various actual implementations of
of_node_to_nid (ppc, sparc and the generic one in of_numa.c) export
the symbol. While the fallback implementation does not because it is
defined as a weak symbol. As a result we'll get this build failure iff
there's a call to of_node_to_nid() in a module.

The one-line fix is just to delete the call to of_node_to_nid() in
of_pmem.c. I have a patch that adds a Kconfig options and removes the
weak symbol games. That needs Acks from the ppc, sparc and DT
maintainers though so it'll take longer to organise.

How about just marking OF_PMEM as bool for the time being until all of
these other reworks land upstream?