Hello All,

Thanks a lot all of you for your support and cooperation...!!

*In case of using YAFFS2 direct interface, do we need MTD interface or
similar layer like MTD? *

Best regards,
Saquib

On Wed, Mar 10, 2010 at 1:31 AM, Charles Manning <manningc2@actrix.gen.nz>wrote:

> Ross has done an excellent job answering questions. I'll just add a few
> more
> comments.
> On Tuesday 09 March 2010 23:45:24 Ross Younger wrote:
> > Saquib wrote:
> > > (1) *YAFFS2 Direct Interface* : What is the use of this interface? Is
> it
> > > mandatory when I use YAFFS2?
> >
> > YAFFS was originally developed as a filesystem module to be loaded into
> the
> > Linux kernel and accessed indirectly via the standard filesystem calls.
> It
> > has since been ported to other platforms including WinCE and eCos. The
> > Direct interface is for use in a system when you have no filesystem
> > interface, or do not want to use your platform's filesystem layer, which
> > would likely only be relevant in very specialised environments.
>
> As Ross says, the Yaffs Direct Interface wraps up the "core yaffs" so that
> the
> code can be used without any specialised OS glue layer. The Linux and eCOS
> ports do not use the Yaffs Direct Interface but instead the OS accesses
> yaffs
> via an OS-specific glue layer. In Linux this is yaffs_fs.c
>
> WinCE yaffs actually is a further wrapper layer around Yaffs Direct
> Interface.
>
> Most people using yaffs with other RTOSs use Yaffs Direct Interface.
>
> Yaffs Direct Interface is also used for building test harnesses where yaffs
> is
> built into an application for easier debugging.
>
> >
> > > (2) *Garbage Collection and Wear-Levelling*: How do I test these things
> > > are working?
> >
> > Set the yaffs_traceMask appropriately, run a stress test, collect the
> > diagnostic output and analyse it to determine whether these features are
> > operating correctly. The tracemask is a bitfield; its bits are named
> > YAFFS_TRACE_* and are defined in yportenv.h.
> >
> > See also http://www.yaffs.net/yaffs-debugging
> >
> > > (3) *4K Page Size* : This chip supports 4K page size. Is there any
> > > changes required in YAFFS2 source code for 4K support.
> >
> > I don't think so, provided the mtd (NAND chip) driver for your chip sets
> up
> > the yaffs_DeviceStruct appropriately.
>
> yaffs supports 4k pages with no changes. Indeed you could use 8k or 16k
> pages
> or even non power of 2 page sizes. One product uses 6k pages (3x2048-byte
> NAND chips in parallel)
>
> >
> > > (4) *Multiplane Programming* : The newer chip we are planning to use is
> > > multiplane NAND chip. How does YAFFS2 support Multiplane chip?
> >
> > YAFFS2 is known to support MLC parts. Others are better placed to comment
> > here, but I think it's largely transparent and would depend on having a
> > good mtd driver which uses the right ECC algorithm. You may need to look
> > carefully at the chip spec sheet to see whether a more complicated ECC
> > algorithm is required for the ECC YAFFS calculates internally on the tags
> > it stores in the spare area of each page.
>
> YAFFS does not provide specific multi-plane support but only accesses one
> page
> at a time.
>
> One way to handle this is to do a single-to-multi-page translation in your
> driver. That could buffer up page writes until there are enough to do a
> multi-plane write or something similar.
>
> -- Charles
>
>
>
>
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