edac: add edac_device_alloc_index()

Add edac_device_alloc_index(), because for MAPLE platform there may
exist several EDAC driver modules that could make use of
edac_device_ctl_info structure at the same time. The index allocation
for these structures should be taken care of by EDAC core.

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Harry Ciao <qingtao.cao@windriver.com>
Cc: Doug Thompson <norsk5@yahoo.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Kumar Gala <galak@gate.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/edac/edac_device.c b/drivers/edac/edac_device.c
index a7d2c71..b02a6a6 100644
--- a/drivers/edac/edac_device.c
+++ b/drivers/edac/edac_device.c
@@ -490,6 +490,20 @@
 	mutex_unlock(&device_ctls_mutex);
 }
 
+/*
+ * edac_device_alloc_index: Allocate a unique device index number
+ *
+ * Return:
+ *	allocated index number
+ */
+int edac_device_alloc_index(void)
+{
+	static atomic_t device_indexes = ATOMIC_INIT(0);
+
+	return atomic_inc_return(&device_indexes) - 1;
+}
+EXPORT_SYMBOL_GPL(edac_device_alloc_index);
+
 /**
  * edac_device_add_device: Insert the 'edac_dev' structure into the
  * edac_device global list and create sysfs entries associated with