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, 43 insertions, 0 deletions

diff --git a/drivers/mtd/mtdbdi.c b/drivers/mtd/mtdbdi.c
new file mode 100644
index 000000000000..5ca5aed0b225
--- /dev/null
+++ b/drivers/mtd/mtdbdi.c
@@ -0,0 +1,43 @@
+/* MTD backing device capabilities
+ *
+ * Copyright © 2006 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/backing-dev.h>
+#include <linux/mtd/mtd.h>
+#include "internal.h"
+
+/*
+ * backing device capabilities for non-mappable devices (such as NAND flash)
+ * - permits private mappings, copies are taken of the data
+ */
+struct backing_dev_info mtd_bdi_unmappable = {
+        .capabilities   = BDI_CAP_MAP_COPY,
+};
+
+/*
+ * backing device capabilities for R/O mappable devices (such as ROM)
+ * - permits private mappings, copies are taken of the data
+ * - permits non-writable shared mappings
+ */
+struct backing_dev_info mtd_bdi_ro_mappable = {
+        .capabilities   = (BDI_CAP_MAP_COPY | BDI_CAP_MAP_DIRECT |
+                           BDI_CAP_EXEC_MAP | BDI_CAP_READ_MAP),
+};
+
+/*
+ * backing device capabilities for writable mappable devices (such as RAM)
+ * - permits private mappings, copies are taken of the data
+ * - permits non-writable shared mappings
+ */
+struct backing_dev_info mtd_bdi_rw_mappable = {
+        .capabilities   = (BDI_CAP_MAP_COPY | BDI_CAP_MAP_DIRECT |
+                           BDI_CAP_EXEC_MAP | BDI_CAP_READ_MAP |
+                           BDI_CAP_WRITE_MAP),
+};