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>

2 files changed, 34 insertions, 0 deletions

diff --git a/drivers/mtd/chips/map_ram.c b/drivers/mtd/chips/map_ram.c
index 072dd8abf33..6bdc50c727e 100644
--- a/drivers/mtd/chips/map_ram.c
+++ b/drivers/mtd/chips/map_ram.c
@@ -21,6 +21,8 @@ static int mapram_write (struct mtd_info *, loff_t, size_t, size_t *, const u_ch
 static int mapram_erase (struct mtd_info *, struct erase_info *);
 static void mapram_nop (struct mtd_info *);
 static struct mtd_info *map_ram_probe(struct map_info *map);
+static unsigned long mapram_unmapped_area(struct mtd_info *, unsigned long,
+                                          unsigned long, unsigned long);
 
 
 static struct mtd_chip_driver mapram_chipdrv = {
@@ -64,6 +66,7 @@ static struct mtd_info *map_ram_probe(struct map_info *map)
         mtd->type = MTD_RAM;
         mtd->size = map->size;
         mtd->erase = mapram_erase;
+        mtd->get_unmapped_area = mapram_unmapped_area;
         mtd->read = mapram_read;
         mtd->write = mapram_write;
         mtd->sync = mapram_nop;
@@ -79,6 +82,20 @@ static struct mtd_info *map_ram_probe(struct map_info *map)
 }
 
 
+/*
+ * 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 mapram_unmapped_area(struct mtd_info *mtd,
+                                          unsigned long len,
+                                          unsigned long offset,
+                                          unsigned long flags)
+{
+        struct map_info *map = mtd->priv;
+        return (unsigned long) map->virt + offset;
+}
+
 static int mapram_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
 {
         struct map_info *map = mtd->priv;
diff --git a/drivers/mtd/chips/map_rom.c b/drivers/mtd/chips/map_rom.c
index c76d6e5f47e..076090a67b9 100644
--- a/drivers/mtd/chips/map_rom.c
+++ b/drivers/mtd/chips/map_rom.c
@@ -20,6 +20,8 @@ static int maprom_write (struct mtd_info *, loff_t, size_t, size_t *, const u_ch
 static void maprom_nop (struct mtd_info *);
 static struct mtd_info *map_rom_probe(struct map_info *map);
 static int maprom_erase (struct mtd_info *mtd, struct erase_info *info);
+static unsigned long maprom_unmapped_area(struct mtd_info *, unsigned long,
+                                          unsigned long, unsigned long);
 
 static struct mtd_chip_driver maprom_chipdrv = {
         .probe  = map_rom_probe,
@@ -40,6 +42,7 @@ static struct mtd_info *map_rom_probe(struct map_info *map)
         mtd->name = map->name;
         mtd->type = MTD_ROM;
         mtd->size = map->size;
+        mtd->get_unmapped_area = maprom_unmapped_area;
         mtd->read = maprom_read;
         mtd->write = maprom_write;
         mtd->sync = maprom_nop;
@@ -53,6 +56,20 @@ static struct mtd_info *map_rom_probe(struct map_info *map)
 }
 
 
+/*
+ * 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 maprom_unmapped_area(struct mtd_info *mtd,
+                                          unsigned long len,
+                                          unsigned long offset,
+                                          unsigned long flags)
+{
+        struct map_info *map = mtd->priv;
+        return (unsigned long) map->virt + offset;
+}
+
 static int maprom_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
 {
         struct map_info *map = mtd->priv;