[Yaffs] i've another question about yaffs2_scan_chunk?

when start up,yaffs scan every chunk of a block that the summary not
written.
when it read the chunk's oob,if it is an empty chunk,the tags it read if
full of 0xff,so the flag chunk_used should not be 0 and the judgement of
"if (!tag.chunk_used)" should never enter, am i right?
so in my understanding ,the function dev->param.read_chunk_tags_fn shoud do
something rather than copy data from flash?

and when writing data to flash,i cannot skip one or more chunks then write
another one?
thansk very much.
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Regards,
Ezio.