[RFC PATCH] mtd: allow mmap for ram devices in memory address space.

[Philippe De Muyter]

Implement mmap for mtd-ram, by using mtd->_get_unmapped_area, as asked by
an ancient comment, to get the physical address (if any) in memory of the
mtd device.

Therefore, mapram_unmapped_area had to be changed to return the physical
address, not the virtual one, For the NOMMU case, that makes no difference,
but for the MMU case, this is needed by mapram_unmapped_area to implement mmap.

Signed-off-by: Philippe De Muyter <phdm at macqel.be>
Cc: David Howells <dhowells at redhat.com>
Cc: Markus Niebel <list-09 at tqsc.de>
---
 drivers/mtd/chips/map_ram.c |    2 +-
 drivers/mtd/mtdchar.c       |   12 +++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/chips/map_ram.c b/drivers/mtd/chips/map_ram.c
index 991c2a1..e93d147 100644
--- a/drivers/mtd/chips/map_ram.c
+++ b/drivers/mtd/chips/map_ram.c
@@ -92,7 +92,7 @@ static unsigned long mapram_unmapped_area(struct mtd_info *mtd,
 					  unsigned long flags)
 {
 	struct map_info *map = mtd->priv;
-	return (unsigned long) map->virt + offset;
+	return (unsigned long) map->phys + offset;
 }
 
 static int mapram_read (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 2147e73..00eac7a 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -1112,13 +1112,23 @@ static int mtdchar_mmap(struct file *file, struct vm_area_struct *vma)
 #ifdef CONFIG_MMU
 	struct mtd_file_info *mfi = file->private_data;
 	struct mtd_info *mtd = mfi->mtd;
-	struct map_info *map = mtd->priv;
+	loff_t offset = vma->vm_pgoff << PAGE_SHIFT;
+	loff_t len = vma->vm_end - vma->vm_start;
 
+	if (offset > mtd->size - len)
+		return (unsigned long) -EINVAL;
+	if (mtd->_get_unmapped_area) {
+		phys_addr_t start;
+
+		start = mtd->_get_unmapped_area(mtd, len, offset, vma->vm_flags);
+		return vm_iomap_memory(vma, start, len);
+	}
         /* This is broken because it assumes the MTD device is map-based
 	   and that mtd->priv is a valid struct map_info.  It should be
 	   replaced with something that uses the mtd_get_unmapped_area()
 	   operation properly. */
 	if (0 /*mtd->type == MTD_RAM || mtd->type == MTD_ROM*/) {
+		struct map_info *map = mtd->priv;
 #ifdef pgprot_noncached
 		if (file->f_flags & O_DSYNC || map->phys >= __pa(high_memory))
 			vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
-- 
1.7.5.3