Sibley and wbuf fixups

[Josh Boyer]

Howdy,

Joern and I were discussing a patch in his tree that merges some of
the ECC'd NOR code in JFFS2 with the code for Sibley flashes that was
put in recently.  The patch can be found here:

http://git.infradead.org/?p=users/joern/mtd-2.6.git;a=commitdiff;h=af97d29fbcc5c4fffdb39f617730e73ad4ce2863

A question came up because the patch removes a fixup for the wbuf that
is needed on ECC'd NOR chips in regards to the cleanmarker size.  The
cleanmarkers on ECC'd NOR chips have to be 16 bytes in length.  This
is because the minimum write size on those chips is 8 bytes.  The
structure is too small to fit in 8 bytes and we need to prevent JFFS2
from trying to write to the last 4 bytes of the second write region,
since those chips prevent writes to a section that has already been
written.  Hence, 16 bytes for a cleanmarker size.

The fixup looks for this and corrects the wbuf offset and length so
that JFFS2 does not throw a non-contiguous write error a bit further
down in the code.  As it stands now, the patch is broken for the ECC'd
NOR chips.  However, our main question is does Sibley need a similar
fixup for the wbuf?  If not, why?

Nico, could you maybe explain that a bit?

josh