[ndctl PATCH 3/8] libncdtl: Add initial support for NVDIMM_FAMILY_PAPR_SCM dimm family

[Vaibhav Jain <vaibhav@linux.ibm.com>]

The patch-set adds necessary scaffolding in libndctl for dimms that
support papr_scm specification[1]. Since there can be platforms that
support Open-Firmware[2] but not the papr_scm specification, hence the
changes proposed first add support for probing if the dimm bus
supports Open-Firmware. This is done via querying for sysfs attribute
'of_node' in dimm device sysfs directory. If available newly
introduced member 'struct ndctl_bus.has_of_node' is set.

During the probe of the dimm and execution of add_dimm(), the newly
introduced add_of_pmem_dimm() is called if dimm bus reports supports
Open-Firmware.

Function add_of_pmem_dimm() queries the 'compatible' device tree
attribute and based on its value assign NVDIMM_FAMILY_PAPR_SCM to the
dimm command family. In future based on the contents of 'compatible'
attribute more of_pmem dimm families can be queried.

Presently the dimm-ops implementation for NVDIMM_FAMILY_PAPR_SCM is
available in global variable 'papr_scm_dimm_ops' which is a NULL
pointer. Subsequent patches will provide a working dimm-ops
implementation pointed to by 'papr_scm_dimm_ops'.

References:
[1] : https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id=58b278f568f0509497e2df7310bfd719156a60d1
[2] : https://en.wikipedia.org/wiki/Open_Firmware

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
 ndctl/lib/libndctl.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 ndctl/lib/private.h  |  2 ++
 ndctl/libndctl.h     |  1 +
 ndctl/ndctl.h        |  1 +
 4 files changed, 46 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index a5f5fdac9f48..650406d27512 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -858,6 +858,12 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
 		bus->revision = strtoul(buf, NULL, 0);
 	}
 
+	sprintf(path, "%s/device/of_node/compatible", ctl_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		bus->has_of_node = 0;
+	else
+		bus->has_of_node = 1;
+
 	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
 		bus->nfit_dsm_mask = 0;
@@ -966,6 +972,10 @@ NDCTL_EXPORT int ndctl_bus_has_nfit(struct ndctl_bus *bus)
 	return bus->has_nfit;
 }
 
+NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
+{
+	return bus->has_of_node;
+}
 /**
  * ndctl_bus_get_major - nd bus character device major number
  * @bus: ndctl_bus instance returned from ndctl_bus_get_{first|next}
@@ -1405,6 +1415,34 @@ static int ndctl_bind(struct ndctl_ctx *ctx, struct kmod_module *module,
 static int ndctl_unbind(struct ndctl_ctx *ctx, const char *devpath);
 static struct kmod_module *to_module(struct ndctl_ctx *ctx, const char *alias);
 
+static int add_of_pmem_dimm(struct ndctl_dimm *dimm, const char *dimm_base)
+{
+	int rc = -ENODEV;
+	char buf[SYSFS_ATTR_SIZE];
+	struct ndctl_ctx *ctx = dimm->bus->ctx;
+	char *path = calloc(1, strlen(dimm_base) + 100);
+
+	dbg(ctx, "Probing of_pmem dimm %d at %s\n", dimm->id, dimm_base);
+
+	if (!path)
+		return -ENOMEM;
+
+	sprintf(path, "%s/../of_node/compatible", dimm_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		goto out;
+
+
+	dbg(ctx, "Compatible of_pmem dimm %d at %s\n", dimm->id, buf);
+	if (strcmp(buf, "ibm,pmemory") == 0) {
+		dimm->cmd_family = NVDIMM_FAMILY_PAPR_SCM;
+		rc = 0;
+		goto out;
+	}
+out:
+	free(path);
+	return rc;
+}
+
 static int add_nfit_dimm(struct ndctl_dimm *dimm, const char *dimm_base)
 {
 	int i, rc = -1;
@@ -1583,6 +1621,8 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
 	if (ndctl_bus_has_nfit(bus)) {
 		dimm->formats = formats;
 		rc = add_nfit_dimm(dimm, dimm_base);
+	} else if (ndctl_bus_has_of_node(bus)) {
+		rc = add_of_pmem_dimm(dimm, dimm_base);
 	}
 
 	if (rc == -ENODEV) {
@@ -1600,6 +1640,8 @@ static void *add_dimm(void *parent, int id, const char *dimm_base)
 		dimm->ops = msft_dimm_ops;
 	if (dimm->cmd_family == NVDIMM_FAMILY_HYPERV)
 		dimm->ops = hyperv_dimm_ops;
+	if (dimm->cmd_family == NVDIMM_FAMILY_PAPR_SCM)
+		dimm->ops = papr_scm_dimm_ops;
 
 	/* Call the dimm initialization function if needed */
 	if (!rc && dimm->ops && dimm->ops->dimm_init)
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index fb7fa47f1f37..16754eda7634 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -167,6 +167,7 @@ struct ndctl_bus {
 	int dimms_init;
 	int regions_init;
 	int has_nfit;
+	int has_of_node;
 	char *bus_path;
 	char *bus_buf;
 	size_t buf_len;
@@ -351,6 +352,7 @@ struct ndctl_dimm_ops * const intel_dimm_ops;
 struct ndctl_dimm_ops * const hpe1_dimm_ops;
 struct ndctl_dimm_ops * const msft_dimm_ops;
 struct ndctl_dimm_ops * const hyperv_dimm_ops;
+struct ndctl_dimm_ops * const papr_scm_dimm_ops;
 
 static inline struct ndctl_bus *cmd_to_bus(struct ndctl_cmd *cmd)
 {
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index 9a53049e7f61..32202654885a 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -119,6 +119,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
              bus = ndctl_bus_get_next(bus))
 struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
 int ndctl_bus_has_nfit(struct ndctl_bus *bus);
+int ndctl_bus_has_of_node(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);
 const char *ndctl_bus_get_devname(struct ndctl_bus *bus);
diff --git a/ndctl/ndctl.h b/ndctl/ndctl.h
index 008f81cdeb9f..426708e1fd9b 100644
--- a/ndctl/ndctl.h
+++ b/ndctl/ndctl.h
@@ -263,6 +263,7 @@ struct nd_cmd_pkg {
 #define NVDIMM_FAMILY_HPE2 2
 #define NVDIMM_FAMILY_MSFT 3
 #define NVDIMM_FAMILY_HYPERV 4
+#define NVDIMM_FAMILY_PAPR_SCM 5
 
 #define ND_IOCTL_CALL			_IOWR(ND_IOCTL, ND_CMD_CALL,\
 					struct nd_cmd_pkg)
-- 
2.24.1
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