[RFC] ubi: updatevol: Support volume to volume update

[Ezequiel Garcia]

This commit adds the support for ubiupdatevol to recieve a UBI volume
as the second parameter. This could be useful to update a UBI volume,
from another UBI volume present in the system, for instance when
a redundant scheme is used.

Not-yet-signed-off-by: Ezequiel Garcia <ezequiel at vanguardiasur.com.ar>
---
Hello,

I'm submitting this patch, to discuss about its inclusion.

If the idea is acceptable we should fix the parameter documentation,
and maybe cleanup the implementation a bit.

One thing to consider, is that this volume to volume update feature
could be moved to the kernel (through yet another ioctl). However,
I think there's no advantage over this simpler approach.

 ubi-utils/ubiupdatevol.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/ubi-utils/ubiupdatevol.c b/ubi-utils/ubiupdatevol.c
index 5096791..6b30210 100644
--- a/ubi-utils/ubiupdatevol.c
+++ b/ubi-utils/ubiupdatevol.c
@@ -212,7 +212,24 @@ static int update_volume(libubi_t libubi, struct ubi_vol_info *vol_info)
 			goto out_free;
 		}
 
-		bytes = st.st_size - args.skip;
+		/* If the argument is a character device and a UBI volume
+		 * we update from it. In this case, skip and size parameters
+		 * are not used.
+		 */
+		if (S_ISCHR(st.st_mode) &&
+		    ubi_probe_node(libubi, args.img) == 2) {
+
+			struct ubi_vol_info src_vol_info;
+
+			err = ubi_get_vol_info(libubi, args.img, &src_vol_info);
+			if (!err)
+				bytes = src_vol_info.data_bytes;
+			else
+				bytes = 0;
+		} else {
+
+			bytes = st.st_size - args.skip;
+		}
 	} else
 		bytes = args.size;
 
-- 
2.0.1