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, 14 insertions, 0 deletions

diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 3aa5d77c2cdb..0c079fd307a5 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -162,6 +162,20 @@ struct mtd_info {
         /* We probably shouldn't allow XIP if the unpoint isn't a NULL */
         void (*unpoint) (struct mtd_info *mtd, loff_t from, size_t len);
 
+        /* Allow NOMMU mmap() to directly map the device (if not NULL)
+         * - return the address to which the offset maps
+         * - return -ENOSYS to indicate refusal to do the mapping
+         */
+        unsigned long (*get_unmapped_area) (struct mtd_info *mtd,
+                                            unsigned long len,
+                                            unsigned long offset,
+                                            unsigned long flags);
+
+        /* Backing device capabilities for this device
+         * - provides mmap capabilities
+         */
+        struct backing_dev_info *backing_dev_info;
+
 
         int (*read) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
         int (*write) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf);