[ndctl PATCH v4 1/4] ndctl: add CXL bus detection

[Dave Jiang <dave.jiang@intel.com>]

Add a CXL bus type, and detect whether a 'dimm' is backed by the CXL
subsystem.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

---
v4:
- Remove libgen.h include
v3:
- Simplify detecting cxl subsystem. (Dan)
v2:
- Improve commit log. (Vishal)
---
 ndctl/lib/libndctl.c   |   29 +++++++++++++++++++++++++++++
 ndctl/lib/libndctl.sym |    1 +
 ndctl/lib/private.h    |    1 +
 ndctl/libndctl.h       |    1 +
 4 files changed, 32 insertions(+)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index ad54f0626510..2b06dc8be81a 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -876,6 +876,24 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
 	return NDCTL_FWA_METHOD_RESET;
 }
 
+static int is_subsys_cxl(const char *subsys)
+{
+	char *path;
+	int rc;
+
+	path = realpath(subsys, NULL);
+	if (!path)
+		return -errno;
+
+	if (!strcmp(subsys, "/sys/bus/cxl"))
+		rc = 1;
+	else
+		rc = 0;
+
+	free(path);
+	return rc;
+}
+
 static void *add_bus(void *parent, int id, const char *ctl_base)
 {
 	char buf[SYSFS_ATTR_SIZE];
@@ -919,6 +937,12 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
 	else
 		bus->has_of_node = 1;
 
+	sprintf(path, "%s/device/../subsys", ctl_base);
+	if (is_subsys_cxl(path))
+		bus->has_cxl = 1;
+	else
+		bus->has_cxl = 0;
+
 	sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
 		bus->nfit_dsm_mask = 0;
@@ -1050,6 +1074,11 @@ NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
 	return bus->has_of_node;
 }
 
+NDCTL_EXPORT int ndctl_bus_has_cxl(struct ndctl_bus *bus)
+{
+	return bus->has_cxl;
+}
+
 NDCTL_EXPORT int ndctl_bus_is_papr_scm(struct ndctl_bus *bus)
 {
 	char buf[SYSFS_ATTR_SIZE];
diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
index 75c32b9d4967..2892544d1985 100644
--- a/ndctl/lib/libndctl.sym
+++ b/ndctl/lib/libndctl.sym
@@ -464,4 +464,5 @@ LIBNDCTL_27 {
 } LIBNDCTL_26;
 LIBNDCTL_28 {
 	ndctl_dimm_disable_master_passphrase;
+	ndctl_bus_has_cxl;
 } LIBNDCTL_27;
diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
index e5c56295556d..46bc8908bd90 100644
--- a/ndctl/lib/private.h
+++ b/ndctl/lib/private.h
@@ -163,6 +163,7 @@ struct ndctl_bus {
 	int regions_init;
 	int has_nfit;
 	int has_of_node;
+	int has_cxl;
 	char *bus_path;
 	char *bus_buf;
 	size_t buf_len;
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index c52e82a6f826..91ef0f42f654 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -133,6 +133,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *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);
+int ndctl_bus_has_cxl(struct ndctl_bus *bus);
 int ndctl_bus_is_papr_scm(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
 unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);