Re: [Yaffs] how to query block state at startup?

On 2012-02-21 07:25, Ross Younger wrote:
> On 21/02/12 19:06, Ezio Zhang wrote:
> > As yaffs just provides a interface for query block鈥檚 state and not
> > implement it,I鈥檓 confused about how to archieve this work EFFICIENTLY.
>
> YAFFS needs to know whether or not the block is marked as bad. It's
> quite common for a NAND driver to keep a table of known-bad blocks (both
> those marked bad at the factory, and those that have worn out in use).
> This is what the Linux MTD layer does. The first time you use a chip,
> you have to scan it looking for factory-bad markers and build up the
> initial table; once you have that, it is stored on the chip (taking up a
> block or two) and is very quick to look up later.
>
> > Some one suggest me to scan the whole flash,but I think it will cost to
> > much time when nand flash is big.
>
> If your nand flash array is really large, you may want to consider
> trading off time for spatial efficiency: use virtual pages and/or
> virtual blocks that are larger than your chip's physical pages and
blocks.
>
>
> Ross
>
>

Thank you. But you may misunderstood my meaning. Bad is not the only state
of a block in yaffs.a block may be ‘full’,’empty’,’need_scan’,’dirty’and
many other states that yaffs defined. What I am not sure is how to jude
these states.

by the way if combine two or more blocks as one may cause many problem.





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Best regards,

Ezio