[PATCH v2 6/7] EDAC: add edac_check_mc_owner() to check MC owner

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

Only a single edac driver can be enabled for EDAC MC.  When ghes_edac
is enabled, a regular edac driver for the CPU type / platform still
attempts to register itself and fails in edac_mc_add_mc().

Add edac_check_mc_owner() so that regular edac drivers can check
the owner of EDAC MC at the beginning of initialization.

Also change the owner check to string comparison from address check.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
---
 drivers/edac/edac_mc.c |   15 ++++++++++++++-
 drivers/edac/edac_mc.h |   12 ++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 4800721..52d8d5e 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -701,6 +701,19 @@ struct mem_ctl_info *edac_mc_find(int idx)
 }
 EXPORT_SYMBOL(edac_mc_find);
 
+/*
+ * Returns:
+ *	1 when EDAC MC is free or owned by the module name
+ *	0 when EDAC MC is owned by other module
+ */
+int edac_check_mc_owner(const char *mod_name)
+{
+	if (edac_mc_owner && strcmp(edac_mc_owner, mod_name))
+		return 0;
+
+	return 1;
+}
+EXPORT_SYMBOL(edac_check_mc_owner);
 
 /* FIXME - should a warning be printed if no error detection? correction? */
 int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
@@ -742,7 +755,7 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
 #endif
 	mutex_lock(&mem_ctls_mutex);
 
-	if (edac_mc_owner && edac_mc_owner != mci->mod_name) {
+	if (!edac_check_mc_owner(mci->mod_name)) {
 		ret = -EPERM;
 		goto fail0;
 	}
diff --git a/drivers/edac/edac_mc.h b/drivers/edac/edac_mc.h
index 5357800..0e95eba 100644
--- a/drivers/edac/edac_mc.h
+++ b/drivers/edac/edac_mc.h
@@ -128,6 +128,18 @@ struct mem_ctl_info *edac_mc_alloc(unsigned mc_num,
 				   unsigned sz_pvt);
 
 /**
+ *
+ * edac_check_mc_owner - Check the owner of EDAC MC
+ *
+ * @mod_name: pointer to the module name
+ *
+ * Returns:
+ *	1 when EDAC MC is free or owned by the module name
+ *	0 when EDAC MC is owned by other module
+ */
+extern int edac_check_mc_owner(const char *mod_name);
+
+/*
  * edac_mc_add_mc_with_groups() - Insert the @mci structure into the mci
  *	global list and create sysfs entries associated with @mci structure.
  *