fs: make it possible to read the filesystem UUID

Some filesystems have a UUID stored in its superblock. To
allow using root=UUID=... for the kernel command line we
need a way to read-out the filesystem UUID.

changes rfc -> v1:
 - make the environment variable an option parameter. If not
   given, the UUID is printed out. If given, it is stored in the env
   variable.
 - corrected typos
 - return error codes

changes v1 -> v2:
 - fix return code of do_fs_uuid(..)
 - document do_fs_uuid(..)
 - implement fs_uuid_unsuported(..) be more consistent with the
   way other optional functionality works

changes v2 -> v3:
 - change ext4fs_uuid(..) to make use of #if .. #else .. #endif
   construct to get rid of unreachable code

Hit any key to stop autoboot:  0
=> fsuuid
fsuuid - Look up a filesystem UUID

Usage:
fsuuid <interface> <dev>:<part>
    - print filesystem UUID
fsuuid <interface> <dev>:<part> <varname>
    - set environment variable to filesystem UUID

=> fsuuid mmc 0:1
d9f9fc05-45ae-4a36-a616-fccce0e4f887
=> fsuuid mmc 0:2
eb3db83c-7b28-499f-95ce-9e0bb21cda81
=> fsuuid mmc 0:1 uuid1
=> fsuuid mmc 0:2 uuid2
=> printenv uuid1
uuid1=d9f9fc05-45ae-4a36-a616-fccce0e4f887
=> printenv uuid2
uuid2=eb3db83c-7b28-499f-95ce-9e0bb21cda81
=>

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Acked-by: Stephen Warren <swarren@nvidia.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/common/cmd_fs_uuid.c b/common/cmd_fs_uuid.c
new file mode 100644
index 0000000000..613f3a4f3d
--- /dev/null
+++ b/common/cmd_fs_uuid.c
@@ -0,0 +1,26 @@
+/*
+ * cmd_fs_uuid.c -- fsuuid command
+ *
+ * Copyright (C) 2014, Bachmann electronic GmbH
+ *
+ * SPDX-License-Identifier:    GPL-2.0+
+ */
+
+#include <common.h>
+#include <command.h>
+#include <fs.h>
+
+static int do_fs_uuid_wrapper(cmd_tbl_t *cmdtp, int flag,
+	int argc, char * const argv[])
+{
+	return do_fs_uuid(cmdtp, flag, argc, argv, FS_TYPE_ANY);
+}
+
+U_BOOT_CMD(
+	fsuuid, 4, 1, do_fs_uuid_wrapper,
+	"Look up a filesystem UUID",
+	"<interface> <dev>:<part>\n"
+	"    - print filesystem UUID\n"
+	"fsuuid <interface> <dev>:<part> <varname>\n"
+	"    - set environment variable to filesystem UUID\n"
+);