[OpenWrt-Devel] Help with SysupgradeNAND

Ben Mulvihill ben.mulvihill at gmail.com
Thu Jul 10 02:27:36 EDT 2014

On Wed, 2014-07-09 at 16:27 +0200, Daniel Golle wrote:
> On Wed, Jul 09, 2014 at 04:10:52PM +0200, Ben Mulvihill wrote:
> > > JFFS2 works on bare MTD devices (originally NOR only, hackish NAND support
> > > exists in the wild though YAFFS2 is more commonly used).
> > > UBIFS is the only read-write filesystem which works on top of UBI, thus the
> > > only possible choice for overlay support.
> > 
> > Not the only possibility surely? Currently we generate two images
> > for the BTHOMEHUBV2B. Both use ubi. One has pure ubifs on top. The
> > other has a squashfs/jffs2 overlay making use of gluebi. Everything 
> > works apart from sysupgrade but the only reason for doing things 
> > that way was that it was a natural progression from the pre-ubi 
> > arrangement and it worked out of the box. A squashfs/ubifs overlay
> > is certainly cleaner. I'll see what I need to do to get it working.
> Ah, ok, now I understand the question :)
> And yes, you should use squashfs/ubifs for overlay and disable gluebi
> alltogether. gluebi is deprectated and was meant only for transition.
> ubiblock offers a much cleaner way for read-only filesystems and UBIFS makes
> much more sense than jffs2-on-gluebi.

The penny has finally dropped! When I first made images using the new 
ubi support a few weeks ago the squashfs/jffs2 gluebi overlay worked
out of the box, and the squashfs/ubifs overlay did not. I assumed I 
would have to generate the squashfs images for the latter case in
some special way, preformatting an empty ubifs partition perhaps,
or adding some magic to tell the kernel to mount rootfs_data as ubifs.
I have just realised  that the images work fine as they are, as long
as the gluebi/mtd code doesn't get there first and attempt a jffs2 
mount. So all that needs to be done to move over to a squashfs/ubifs 
overlay is to disable gluebi in the kernel configuration. I should
like to ask John whether he would be happy for me to submit a patch
to do that, on xway at least, not on xrx200 to avoid affecting the
other lantiq nand boards?

Or would it be better to find some way of enabling the volume_identify
code in procd to distinguish a jffs2 rootfs_data from a ubifs 
rootfs_data. just in case in the future someone needs gluebi in
the kernel for some other reason?

Thank you 

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