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/drivers/mtd/devices/mtdram.c b/drivers/mtd/devices/mtdram.c
index 3aaca88847d3..fce5ff7589aa 100644
--- a/drivers/mtd/devices/mtdram.c
+++ b/drivers/mtd/devices/mtdram.c
@@ -65,6 +65,19 @@ static void ram_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
+ */
+static unsigned long ram_get_unmapped_area(struct mtd_info *mtd,
+                                           unsigned long len,
+                                           unsigned long offset,
+                                           unsigned long flags)
+{
+        return (unsigned long) mtd->priv + offset;
+}
+
 static int ram_read(struct mtd_info *mtd, loff_t from, size_t len,
                 size_t *retlen, u_char *buf)
 {
@@ -116,6 +129,7 @@ int mtdram_init_device(struct mtd_info *mtd, void *mapped_address,
         mtd->erase = ram_erase;
         mtd->point = ram_point;
         mtd->unpoint = ram_unpoint;
+        mtd->get_unmapped_area = ram_get_unmapped_area;
         mtd->read = ram_read;
         mtd->write = ram_write;