[PATCH 3/3] init: auto-create ubiblock device for non-UBIFS rootfs on UBI

[Daniel Golle <daniel@makrotopia.org>]

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 init/do_mounts.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 55 insertions(+), 7 deletions(-)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index dea5de9..485df12 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -28,6 +28,7 @@
 #include <linux/slab.h>
 #include <linux/ramfs.h>
 #include <linux/shmem_fs.h>
+#include <linux/mtd/ubi.h>
 
 #include <linux/nfs_fs.h>
 #include <linux/nfs_fs_sb.h>
@@ -179,6 +180,47 @@ done:
 }
 #endif
 
+#if defined(CONFIG_MTD_UBI_BLOCK) && !defined(CONFIG_MTD_UBI_MODULE)
+#define UBIFS_NODE_MAGIC  0x06101831
+static inline int ubi_vol_is_ubifs(struct ubi_volume_desc *desc)
+{
+	int ret;
+	uint32_t magic_of, magic;
+	ret = ubi_read(desc, 0, (char *)&magic_of, 0, 4);
+	if (ret)
+		return 0;
+	magic = le32_to_cpu(magic_of);
+	return magic == UBIFS_NODE_MAGIC;
+}
+
+static void ubiblock_create_rootdev(char *name)
+{
+	int ret, is_ubifs;
+	struct ubi_volume_desc *desc;
+	struct ubi_volume_info vi;
+	dev_t bdev;
+
+	desc = ubi_open_volume_str(name, UBI_READONLY);
+	if (IS_ERR(desc))
+		return;
+
+	ubi_get_volume_info(desc, &vi);
+
+	is_ubifs = ubi_vol_is_ubifs(desc);
+	ubi_close_volume(desc);
+
+	if (is_ubifs)
+		return;
+
+	ret = ubiblock_create_dev(&vi, &bdev);
+	if (!ret) {
+		pr_notice("ubiblock%u_%u: '%s' set to be root filesystem\n",
+			  vi.ubi_num, vi.vol_id, vi.name);
+		ROOT_DEV = bdev;
+	}
+}
+#endif
+
 /*
  *	Convert a name into device number.  We accept the following variants:
  *
@@ -569,14 +611,20 @@ void __init prepare_namespace(void)
 
 	if (saved_root_name[0]) {
 		root_device_name = saved_root_name;
-		if (!strncmp(root_device_name, "mtd", 3) ||
-		    !strncmp(root_device_name, "ubi", 3)) {
-			mount_block_root(root_device_name, root_mountflags);
-			goto out;
+#if defined(CONFIG_MTD_UBI_BLOCK) && !defined(CONFIG_MTD_UBI_MODULE)
+		if (!strncmp(root_device_name, "ubi", 3))
+			ubiblock_create_rootdev(root_device_name);
+#endif
+		if (ROOT_DEV == 0) {
+			if (!strncmp(root_device_name, "mtd", 3) ||
+			    !strncmp(root_device_name, "ubi", 3)) {
+				mount_block_root(root_device_name, root_mountflags);
+				goto out;
+			}
+			ROOT_DEV = name_to_dev_t(root_device_name);
+			if (strncmp(root_device_name, "/dev/", 5) == 0)
+				root_device_name += 5;
 		}
-		ROOT_DEV = name_to_dev_t(root_device_name);
-		if (strncmp(root_device_name, "/dev/", 5) == 0)
-			root_device_name += 5;
 	}
 
 	if (initrd_load())
-- 
2.9.3