[U-Boot] dfu: dfu and UBI Volumes

[Tom Rini]

On Wed, May 29, 2013 at 06:35:27AM +0200, Heiko Schocher wrote:

> Hello Tom,
> 
> Am 28.05.2013 23:16, schrieb Tom Rini:
> > On Tue, May 28, 2013 at 11:01:09PM +0200, Wolfgang Denk wrote:
> >> Dear Tom,
> >>
> >> In message <20130528172309.GF5829 at bill-the-cat> you wrote:
> >>>
> >>>> Of course this can't yet apply to writing files on file systems since the
> >>>> current API in U-Boot misses the append feature, but this could be applied to
> >>>> program raw memory partitions, including UBI images.
> >>>
> >>> Correct.  We can write a whole UBI image, today, of NAND size,
> >>> regardless of DDR size.  But modifying UBI volumes (so UBIFS or your
> >>
> >> I don't think so.  To write a UBI volume on an existing UBI device,
> >> you would use the "ubi write" command.  This translates into a call of
> >> ubi_volume_write(char *volume, void *buf, size_t size)  which means
> >> the size must be known before you start writing; as far as I can tell
> >> ubi_volume_write() does not support incremental write operations of
> >> individual "parts" of a volume.
> > 
> > OK.  A very quick read of ubi_volume_write leads into the guts of the
> > write being in drivers/mtd/ubi/upd.c and it feels like you could
> > actually do the volume write in chunks with ubi_start_update() and
> > ubi_more_update_data() (and maybe some other housekeeping bits).  It
> > might take a bit more work since it looks like looks like both functions
> > rely on knowing the size at the start, but that's just to make sure the
> > size will fit in the volume.
> 
> Yes, I think so too ... seems some work, but not unsolveable ...
> 
> Hmm.. is it possible to get the filesize over dfu on startup? (I hope
> so, as it makes no sense to transfer a file, if it does not fit in the
> partition ... )

There is not, but that's OK.  Even if you think you had the room for the
whole image you could find a new bad block and not fit, so it's just
behaving like when we do a raw NAND write, get the data chunk, make sure
we think we still have room, write if we do, error if we don't.

-- 
Tom
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