Re: Support of removable MTD devices and other advanced features (follow-up from lkml)

Alex Dubov
2008-05-25T03:41:19Z

--- Jörn Engel <joern@logfs.org> wrote:

> On Sat, 24 May 2008 06:12:23 -0700, Alex Dubov wrote:
> >
> > Do UBI and JFFS always operate in terms of whole eraseblocks or they may
> > attempt partial block writes? Different flash chips have different
> > capabilities in regard to writing and this can be used to some advantage.
>
> Writes happen in multiples of mtd->writesize. Which for NAND is
> pagesize. There are also special cases with subpage writes. AFAIK only
> UBI exploits that feature.
>

Most xd cards can only be written a whole PEB in a time (can be handled with
appropriate writesize, I suppose).

Memorystick cards can be written page at a time, but only in progressive
fashion - only if all pages at lower offsets to the current page were written
before. This can be made to work as a useful optimization.

Are there any special tricks with subpage writes or it all amounts to "read
block" -> "merge changes" -> "write block"?