[PATCH v10 4/6] powerpc/papr_scm: Improve error logging and handling papr_scm_ndctl()

[Vaibhav Jain]

Since papr_scm_ndctl() can be called from outside papr_scm, its
exposed to the possibility of receiving NULL as value of 'cmd_rc'
argument. This patch updates papr_scm_ndctl() to protect against such
possibility by assigning it pointer to a local variable in case cmd_rc
== NULL.

Finally the patch also updates the 'default' clause of the switch-case
block removing a 'return' statement thereby ensuring that value of
'cmd_rc' is always logged when papr_scm_ndctl() returns.

Cc: "Aneesh Kumar K . V" <aneesh.kumar at linux.ibm.com>
Cc: Dan Williams <dan.j.williams at intel.com>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Ira Weiny <ira.weiny at intel.com>
Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
Changelog:

v9..v10
* New patch in the series
---
 arch/powerpc/platforms/pseries/papr_scm.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 0c091622b15e..6512fe6a2874 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -355,11 +355,16 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
 {
 	struct nd_cmd_get_config_size *get_size_hdr;
 	struct papr_scm_priv *p;
+	int rc;
 
 	/* Only dimm-specific calls are supported atm */
 	if (!nvdimm)
 		return -EINVAL;
 
+	/* Use a local variable in case cmd_rc pointer is NULL */
+	if (!cmd_rc)
+		cmd_rc = &rc;
+
 	p = nvdimm_provider_data(nvdimm);
 
 	switch (cmd) {
@@ -381,12 +386,13 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
 		break;
 
 	default:
-		return -EINVAL;
+		dev_dbg(&p->pdev->dev, "Unknown command = %d\n", cmd);
+		*cmd_rc = -EINVAL;
 	}
 
 	dev_dbg(&p->pdev->dev, "returned with cmd_rc = %d\n", *cmd_rc);
 
-	return 0;
+	return *cmd_rc;
 }
 
 static ssize_t flags_show(struct device *dev,
-- 
2.26.2