[PATCH] libnvdimm: Fix nvdimm_probe error on NVDIMM-N

[Toshi Kani <toshi.kani@hpe.com>]

'ndctl list --buses --dimms' does not list any NVDIMM-Ns since
they are considered as idle.  ndctl checks if any driver is
attached to nmem device.  nvdimm_probe() always fails in
nvdimm_init_nsarea() since NVDIMM-Ns do not implement optinal
ND_CMD_GET_CONFIG_DATA command.

Change nvdimm_probe() to accept the case that the CONFIG_DATA
command is not implemented for NVDIMM-Ns.  The driver attaches
without ndd, which keeps it no-op to the device.

Reported-by: Brian Boylston <brian.boylston@hpe.com>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Dan Williams <dan.j.williams@intel.com>
---
 drivers/nvdimm/dimm.c      |   10 ++++++++++
 drivers/nvdimm/dimm_devs.c |   27 ++++++++++++++++-----------
 drivers/nvdimm/nd.h        |    1 +
 3 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/nvdimm/dimm.c b/drivers/nvdimm/dimm.c
index 71d12bb..07e09c2 100644
--- a/drivers/nvdimm/dimm.c
+++ b/drivers/nvdimm/dimm.c
@@ -26,6 +26,13 @@ static int nvdimm_probe(struct device *dev)
 	struct nvdimm_drvdata *ndd;
 	int rc;
 
+	rc = nvdimm_check_config_data(dev);
+	if (rc == -ENOENT)
+		/* not required for non-aliased nvdimm, ex. NVDIMM-N */
+		return 0;
+	else
+		return rc;
+
 	ndd = kzalloc(sizeof(*ndd), GFP_KERNEL);
 	if (!ndd)
 		return -ENOMEM;
@@ -72,6 +79,9 @@ static int nvdimm_remove(struct device *dev)
 {
 	struct nvdimm_drvdata *ndd = dev_get_drvdata(dev);
 
+	if (!ndd)
+		return 0;
+
 	nvdimm_bus_lock(dev);
 	dev_set_drvdata(dev, NULL);
 	nvdimm_bus_unlock(dev);
diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index d9bba5e..fee82d3 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -28,28 +28,33 @@ static DEFINE_IDA(dimm_ida);
  * Retrieve bus and dimm handle and return if this bus supports
  * get_config_data commands
  */
-static int __validate_dimm(struct nvdimm_drvdata *ndd)
+int nvdimm_check_config_data(struct device *dev)
 {
-	struct nvdimm *nvdimm;
-
-	if (!ndd)
-		return -EINVAL;
-
-	nvdimm = to_nvdimm(ndd->dev);
+	struct nvdimm *nvdimm = to_nvdimm(dev);
 
 	if (!nvdimm->cmd_mask)
-		return -ENXIO;
+		goto err;
 	if (!test_bit(ND_CMD_GET_CONFIG_DATA, &nvdimm->cmd_mask))
-		return -ENXIO;
+		goto err;
 
 	return 0;
+
+ err:
+	if (nvdimm->flags & NDD_ALIASING)
+		return -ENXIO;
+	else
+		return -ENOENT;
 }
 
 static int validate_dimm(struct nvdimm_drvdata *ndd)
 {
-	int rc = __validate_dimm(ndd);
+	int rc;
 
-	if (rc && ndd)
+	if (!ndd)
+		return -EINVAL;
+
+	rc = nvdimm_check_config_data(ndd->dev);
+	if (rc)
 		dev_dbg(ndd->dev, "%pf: %s error: %d\n",
 				__builtin_return_address(0), __func__, rc);
 	return rc;
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 8024a0e..38d6f03 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -191,6 +191,7 @@ void nvdimm_exit(void);
 void nd_region_exit(void);
 struct nvdimm;
 struct nvdimm_drvdata *to_ndd(struct nd_mapping *nd_mapping);
+int nvdimm_check_config_data(struct device *dev);
 int nvdimm_init_nsarea(struct nvdimm_drvdata *ndd);
 int nvdimm_init_config_data(struct nvdimm_drvdata *ndd);
 int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,