On 21/02/12 19:06, Ezio Zhang wrote:
> As yaffs just provides a interface for query block’s state and not
> implement it,I’m 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