Dan Williams [off-list ref] writes:

On Tue, Mar 22, 2022 at 7:30 AM kajoljain [off-list ref] wrote:

quoted

On 3/22/22 03:09, Dan Williams wrote:

quoted

On Fri, Mar 18, 2022 at 4:42 AM Kajol Jain [off-list ref] wrote:

quoted

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

arch/powerpc/platforms/pseries/papr_scm.c:372:35: error: ‘struct perf_event’ has no member named ‘attr’
         p->nvdimm_events_map[event->attr.config],
                                   ^~
In file included from ./include/linux/list.h:5,
                 from ./include/linux/kobject.h:19,
                 from ./include/linux/of.h:17,
                 from arch/powerpc/platforms/pseries/papr_scm.c:5:
arch/powerpc/platforms/pseries/papr_scm.c: In function ‘papr_scm_pmu_event_init’:
arch/powerpc/platforms/pseries/papr_scm.c:389:49: error: ‘struct perf_event’ has no member named ‘pmu’
  struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
                                                 ^~
./include/linux/container_of.h:18:26: note: in definition of macro ‘container_of’
  void *__mptr = (void *)(ptr);     \
                          ^~~
arch/powerpc/platforms/pseries/papr_scm.c:389:30: note: in expansion of macro ‘to_nvdimm_pmu’
  struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
                              ^~~~~~~~~~~~~
In file included from ./include/linux/bits.h:22,
                 from ./include/linux/bitops.h:6,
                 from ./include/linux/of.h:15,
                 from arch/powerpc/platforms/pseries/papr_scm.c:5:

Fix the build issue by adding check for CONFIG_PERF_EVENTS config option
and disabling the papr_scm perf interface support incase this config
is not set

Fixes: 4c08d4bbc089 ("powerpc/papr_scm: Add perf interface support") (Commit id
based on linux-next tree)
Signed-off-by: Kajol Jain <redacted>
---
 arch/powerpc/platforms/pseries/papr_scm.c | 15 +++++++++++++++

This is a bit messier than I would have liked mainly because it dumps
a bunch of ifdefery into a C file contrary to coding style, "Wherever
possible, don't use preprocessor conditionals (#if, #ifdef) in .c
files". I would expect this all to move to an organization like:

Hi Dan,
      Thanks for reviewing the patches. Inorder to avoid the multiple
ifdefs checks, we can also add stub function for papr_scm_pmu_register.
With that change we will just have one ifdef check for
CONFIG_PERF_EVENTS config in both papr_scm.c and nd.h file. Hence we can
avoid adding new files specific for papr_scm perf interface.

Below is the code snippet for that change, let me know if looks fine to
you. I tested it
with set/unset PAPR_SCM config value and set/unset PERF_EVENTS config
value combinations.

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c

b/arch/powerpc/platforms/pseries/papr_scm.c
index 4dd513d7c029..38fabb44d3c3 100644

--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c

@@ -69,8 +69,6 @@
 #define PAPR_SCM_PERF_STATS_EYECATCHER __stringify(SCMSTATS)
 #define PAPR_SCM_PERF_STATS_VERSION 0x1

-#define to_nvdimm_pmu(_pmu)    container_of(_pmu, struct nvdimm_pmu, pmu)
-
 /* Struct holding a single performance metric */
 struct papr_scm_perf_stat {
        u8 stat_id[8];

@@ -346,6 +344,9 @@ static ssize_t drc_pmem_query_stats(struct

papr_scm_priv *p,
        return 0;
 }

+#ifdef CONFIG_PERF_EVENTS
+#define to_nvdimm_pmu(_pmu)    container_of(_pmu, struct nvdimm_pmu, pmu)
+
 static int papr_scm_pmu_get_value(struct perf_event *event, struct
device *dev, u64 *count)
 {
        struct papr_scm_perf_stat *stat;

@@ -558,6 +559,10 @@ static void papr_scm_pmu_register(struct

papr_scm_priv *p)
        dev_info(&p->pdev->dev, "nvdimm pmu didn't register rc=%d\n", rc);
 }

+#else
+static inline void papr_scm_pmu_register(struct papr_scm_priv *p) { }

Since this isn't in a header file, it does not need to be marked
"inline" the compiler will figure it out.

quoted

+#endif

It might be time to create:

arch/powerpc/platforms/pseries/papr_scm.h

...there is quite a bit of header material accrued in papr_scm.c and
once the ifdefs start landing in it then it becomes a nominal coding
style issue. That said, this is certainly more palatable than the
previous version. So if you don't want to create papr_scm.h yet for
this, at least make a note in the changelog that the first portion of
arch/powerpc/platforms/pseries/papr_scm.c is effectively papr_scm.h
content and may move there in the future, or something like that.

Great suggestion Dan and incidently we are already working on a patchset
to reconcile this by moving a bunch of these defines from papr_scm.c to a
header. That work is primarily done to towards remove the redundancy
between papr_scm and generic ndtest module that we have today. We will
post the patches in next few days.

-- 
Cheers
~ Vaibhav