[PATCH v8 1/7] libcxl: Add debugfs path to CXL context

[Ben Cheatham <Benjamin.Cheatham@amd.com>]

Find the CXL debugfs mount point and add it to the CXL library context.
This will be used by poison and procotol error library functions to
access the information presented by the filesystem.

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
---
 cxl/lib/libcxl.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
index 32728de..6b7e92c 100644
--- a/cxl/lib/libcxl.c
+++ b/cxl/lib/libcxl.c
@@ -8,6 +8,8 @@
 #include <stdlib.h>
 #include <dirent.h>
 #include <unistd.h>
+#include <mntent.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -54,6 +56,7 @@ struct cxl_ctx {
 	struct kmod_ctx *kmod_ctx;
 	struct daxctl_ctx *daxctl_ctx;
 	void *private_data;
+	char *cxl_debugfs;
 };
 
 static void free_pmem(struct cxl_pmem *pmem)
@@ -240,6 +243,38 @@ CXL_EXPORT void *cxl_get_private_data(struct cxl_ctx *ctx)
 	return ctx->private_data;
 }
 
+static char* get_cxl_debugfs_dir(void)
+{
+	char *debugfs_dir = NULL;
+	struct mntent *ent;
+	FILE *mntf;
+
+	mntf = setmntent("/proc/mounts", "r");
+	if (!mntf)
+		return NULL;
+
+	while ((ent = getmntent(mntf)) != NULL) {
+		if (!strcmp(ent->mnt_type, "debugfs")) {
+			/* Magic '5' here is length of "/cxl" + NULL terminator */
+			debugfs_dir = calloc(strlen(ent->mnt_dir) + 5, 1);
+			if (!debugfs_dir)
+				return NULL;
+
+			strcpy(debugfs_dir, ent->mnt_dir);
+			strcat(debugfs_dir, "/cxl");
+			if (access(debugfs_dir, F_OK) != 0) {
+				free(debugfs_dir);
+				debugfs_dir = NULL;
+			}
+
+			break;
+		}
+	}
+
+	endmntent(mntf);
+	return debugfs_dir;
+}
+
 /**
  * cxl_new - instantiate a new library context
  * @ctx: context to establish
@@ -295,6 +330,7 @@ CXL_EXPORT int cxl_new(struct cxl_ctx **ctx)
 	c->udev = udev;
 	c->udev_queue = udev_queue;
 	c->timeout = 5000;
+	c->cxl_debugfs = get_cxl_debugfs_dir();
 
 	return 0;
 
@@ -350,6 +386,7 @@ CXL_EXPORT void cxl_unref(struct cxl_ctx *ctx)
 	kmod_unref(ctx->kmod_ctx);
 	daxctl_unref(ctx->daxctl_ctx);
 	info(ctx, "context %p released\n", ctx);
+	free((void *)ctx->cxl_debugfs);
 	free(ctx);
 }
 
-- 
2.52.0