NOMMU: Present backing device capabilities for MTD chardevs

Present backing device capabilities for MTD character device files to allow
NOMMU mmap to do direct mapping where possible.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Bernd Schmidt <bernd.schmidt@analog.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 76fe0a1e7a5e..65a7f3703881 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -19,6 +19,7 @@
 #include <linux/proc_fs.h>
 
 #include <linux/mtd/mtd.h>
+#include "internal.h"
 
 #include "mtdcore.h"
 
@@ -46,6 +47,20 @@ int add_mtd_device(struct mtd_info *mtd)
 {
         int i;
 
+        if (!mtd->backing_dev_info) {
+                switch (mtd->type) {
+                case MTD_RAM:
+                        mtd->backing_dev_info = &mtd_bdi_rw_mappable;
+                        break;
+                case MTD_ROM:
+                        mtd->backing_dev_info = &mtd_bdi_ro_mappable;
+                        break;
+                default:
+                        mtd->backing_dev_info = &mtd_bdi_unmappable;
+                        break;
+                }
+        }
+
         BUG_ON(mtd->writesize == 0);
         mutex_lock(&mtd_table_mutex);