Extern or forward variable declaration at include/linux/libnvdimm.h, line 143 References: arch/powerpc/platforms/pseries/papr_scm.c, line 897 drivers/acpi/nfit/core.c, line 3630 drivers/md/dm-writecache.c, line 2523 drivers/nvdimm/bus.c, line 54 drivers/nvdimm/bus.c, line 60 drivers/nvdimm/bus.c, line 83 drivers/nvdimm/bus.c, line 114 drivers/nvdimm/bus.c, line 607 drivers/nvdimm/virtio_pmem.c, line 69 include/linux/libnvdimm.h, line 82 include/linux/libnvdimm.h, line 82 include/linux/libnvdimm.h, line 143 tools/testing/nvdimm/test/nfit.c, line 2929 tools/testing/nvdimm/test/nfit.c, line 3218