[U-Boot] dfu: dfu and UBI Volumes

[Tom Rini]

On Mon, May 27, 2013 at 07:29:02PM +0300, Pantelis Antoniou wrote:
> Hi
> 
> On May 27, 2013, at 7:25 PM, Wolfgang Denk wrote:
> 
> > Dear Heiko Schocher,
> > 
> > In message <51A30F34.7030603 at denx.de> you wrote:
> >> 
> >> But how to handle a raw nand partition and a ubi partition on one
> >> nand?
> >> 
> >> If ubi is a new dfu interface, somebody must start dfu on u-boot
> >> with "dfu nand .." or "dfu ubi .." dependent on which partition
> >> has to be updated ... before using dfu-util on the host side ...
> >> and start dfu-util for the correct partition...
> >> 
> >> This seems not really userfriendly to me ... if I have to use the
> > 
> > Indeed, this makes no sense and breaks the whole concept of DFU to be
> > able to download a sinlge firmware image with one, simple command.
> > 
> >> Is ubi really a "interface" as nand or mmc ... ?
> > 
> > No, it is not.  It could be considered a "partition type" at best.
> > 
> >>> Looks like it's simple enough; erase (but don't step over the wear counters)
> >>> , write (but skip over the wear counters).
> >> 
> >> Yep, or load the complete image in ram, and write it with "ubi write ..."
> > 
> > Not "or".  When dealing with UBI volumes, then "ubi write" (or the
> > equivalent C API) is the way to go.
> > 
> > 
> 
> I pretty much agree. UBI looks like it's partition type.
> 
> BTW, the whole point of DFU is not to store your image in RAM at all.
> There are very few systems that have that much RAM.

This _may_ be the hard part for UBI.  When doing raw block writes for
NAND/MMC, we're able to write them out quickly and thus support images
larger than RAM.  But for filesystems we don't support that notion in
general for write and so limit ourselves to 8MiB or so files.  Fine for
the most part, but not fine for UBI.  It's possible that we can support
this on UBI easier than we can on filesystems, but I just don't know.

-- 
Tom
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