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. ---- Regards, Ezio.