drivers/edac: add edac_mc_find API

This simple patch adds an important CORE API for EDAC that EDAC drivers can
use to find their edac_mc control structure by passing a mem_ctl_info
'instance' value

Needed for subsequent patches
Signed-off-by: Douglas Thompson <dougthompson@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/edac/edac_mc.c

@@ -1456,6 +1456,34 @@ static void del_mc_from_global_list(struct mem_ctl_info *mci)
 	wait_for_completion(&mci->complete);
 }
 
+/**
+ * edac_mc_find: Search for a mem_ctl_info structure whose index is 'idx'.
+ *
+ * If found, return a pointer to the structure.
+ * Else return NULL.
+ *
+ * Caller must hold mem_ctls_mutex.
+ */
+struct mem_ctl_info * edac_mc_find(int idx)
+{
+	struct list_head *item;
+	struct mem_ctl_info *mci;
+
+	list_for_each(item, &mc_devices) {
+		mci = list_entry(item, struct mem_ctl_info, link);
+
+		if (mci->mc_idx >= idx) {
+			if (mci->mc_idx == idx)
+				return mci;
+
+			break;
+		}
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL(edac_mc_find);
+
 /**
  * edac_mc_add_mc: Insert the 'mci' structure into the mci global list and
  *                 create sysfs entries associated with mci structure

drivers/edac/edac_mc.h

@@ -430,6 +430,7 @@ void edac_mc_dump_mci(struct mem_ctl_info *mci);
 void edac_mc_dump_csrow(struct csrow_info *csrow);
 #endif  /* CONFIG_EDAC_DEBUG */
 
+extern struct mem_ctl_info * edac_mc_find(int idx);
 extern int edac_mc_add_mc(struct mem_ctl_info *mci,int mc_idx);
 extern struct mem_ctl_info * edac_mc_del_mc(struct device *dev);
 extern int edac_mc_find_csrow_by_page(struct mem_ctl_info *mci,