[v2 PATCH 1/2] drivers/nvdimm: Fix build failure when CONFIG_PERF_EVENTS is not set

[Kajol Jain <kjain@linux.ibm.com>]

The following build failure occurs when CONFIG_PERF_EVENTS is not set
as generic pmu functions are not visible in that scenario.

|-- s390-randconfig-r044-20220313
|   |-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_migrate_context
|   |-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_register
|   `-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_unregister

Similar build failure in nds32 architecture:
nd_perf.c:(.text+0x21e): undefined reference to `perf_pmu_migrate_context'
nd_perf.c:(.text+0x434): undefined reference to `perf_pmu_register'
nd_perf.c:(.text+0x57c): undefined reference to `perf_pmu_unregister'

Fix this issue by adding check for CONFIG_PERF_EVENTS config option
and disabling the nvdimm perf interface incase this config is not set.

Also remove function declaration of perf_pmu_migrate_context,
perf_pmu_register, perf_pmu_unregister functions from nd.h as these are
common pmu functions which are part of perf_event.h and since we
are disabling nvdimm perf interface incase CONFIG_PERF_EVENTS option
is not set, we not need to declare them in nd.h

Also move the platform_device header file addition part from nd.h to
nd_perf.c and add stub functions for register_nvdimm_pmu and
unregister_nvdimm_pmu functions to handle CONFIG_PERF_EVENTS=n
case.

Fixes: 0fab1ba6ad6b ("drivers/nvdimm: Add perf interface to expose
nvdimm performance stats") (Commit id based on libnvdimm-for-next tree)
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Link: https://lore.kernel.org/all/62317124.YBQFU33+s%2FwdvWGj%25lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
---
 drivers/nvdimm/Makefile  |  2 +-
 drivers/nvdimm/nd_perf.c |  1 +
 include/linux/nd.h       | 16 ++++++++++++----
 3 files changed, 14 insertions(+), 5 deletions(-)

---
Changelog:

v1 -> v2
- Rebase and tested the fix patch changes on top of libnvdimm-for-next branch

- Add stub functions for register_nvdimm_pmu and unregister_nvdimm_pmu
  functions to handle CONFIG_PERF_EVENTS=n case as suggested by Dan Williams

- Move the platform_device header file addition part from nd.h to
  nd_perf.c and just forward declare struct platform_device in nd.h
---

diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
index 3fb806748716..ba0296dca9db 100644
--- a/drivers/nvdimm/Makefile
+++ b/drivers/nvdimm/Makefile
@@ -15,7 +15,7 @@ nd_e820-y := e820.o
 libnvdimm-y := core.o
 libnvdimm-y += bus.o
 libnvdimm-y += dimm_devs.o
-libnvdimm-y += nd_perf.o
+libnvdimm-$(CONFIG_PERF_EVENTS) += nd_perf.o
 libnvdimm-y += dimm.o
 libnvdimm-y += region_devs.o
 libnvdimm-y += region.o
diff --git a/drivers/nvdimm/nd_perf.c b/drivers/nvdimm/nd_perf.c
index 314415894acf..433bbb68ae64 100644
--- a/drivers/nvdimm/nd_perf.c
+++ b/drivers/nvdimm/nd_perf.c
@@ -10,6 +10,7 @@
 #define pr_fmt(fmt) "nvdimm_pmu: " fmt
 
 #include <linux/nd.h>
+#include <linux/platform_device.h>
 
 #define EVENT(_name, _code)     enum{_name = _code}
 
diff --git a/include/linux/nd.h b/include/linux/nd.h
index 7b2ccbdc1cbc..f3e91c891cbc 100644
--- a/include/linux/nd.h
+++ b/include/linux/nd.h
@@ -9,7 +9,6 @@
 #include <linux/device.h>
 #include <linux/badblocks.h>
 #include <linux/perf_event.h>
-#include <linux/platform_device.h>
 
 enum nvdimm_event {
 	NVDIMM_REVALIDATE_POISON,
@@ -57,15 +56,24 @@ struct nvdimm_pmu {
 	struct cpumask arch_cpumask;
 };
 
+struct platform_device;
+
+#ifdef CONFIG_PERF_EVENTS
 extern ssize_t nvdimm_events_sysfs_show(struct device *dev,
 					struct device_attribute *attr,
 					char *page);
 
 int register_nvdimm_pmu(struct nvdimm_pmu *nvdimm, struct platform_device *pdev);
 void unregister_nvdimm_pmu(struct nvdimm_pmu *nd_pmu);
-void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu);
-int perf_pmu_register(struct pmu *pmu, const char *name, int type);
-void perf_pmu_unregister(struct pmu *pmu);
+
+#else
+static inline int register_nvdimm_pmu(struct nvdimm_pmu *nvdimm, struct platform_device *pdev)
+{
+	return -ENXIO;
+}
+
+static inline void unregister_nvdimm_pmu(struct nvdimm_pmu *nd_pmu) { }
+#endif
 
 struct nd_device_driver {
 	struct device_driver drv;
-- 
2.31.1