Re: [Yaffs] bad block management

> Hi
>
> I have review the yaffs2 source code and have a doubt. See the follow
>
>
>
> In Yaffs2 the read interface is yaffs_rd_chunk_tags_nand int 
> yaffs_rd_chunk_tags_nand(struct yaffs_dev *dev, int nand_chunk,
>
>                        u8 *buffer, struct yaffs_ext_tags *tags) {
>
>       .........
>
>       result = dev->tagger.read_chunk_tags_fn(dev, flash_chunk, 
> buffer, tags);
>
>       if (tags && tags->ecc_result > YAFFS_ECC_RESULT_NO_ERROR) {
>
>
>
>             struct yaffs_block_info *bi;
>
>             bi = yaffs_get_block_info(dev,
>
>                                 nand_chunk /
>
>                                 dev->param.chunks_per_block);
>
>             yaffs_handle_chunk_error(dev, bi);
>
>       }
>
>       return result;
>
> }
>
>
>
> The yaffs_rd_chunk_tags_nand will call the mtd interface mtd_read_oob
>
>
>
> int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops
> *ops) {
>
>       int ret_code;
>
>       ops->retlen = ops->oobretlen = 0;
>
>       if (!mtd->_read_oob)
>
>             return -EOPNOTSUPP;
>
>       /*
>
>       * In cases where ops->datbuf != NULL, mtd->_read_oob() has 
> semantics
>
>       * similar to mtd->_read(), returning a non-negative integer
>
>       * representing max bitflips. In other cases, mtd->_read_oob() 
> may
>
>       * return -EUCLEAN. In all cases, perform similar logic to mtd_read().
>
>       */
>
>       ret_code = mtd->_read_oob(mtd, from, ops);
>
>       if (unlikely(ret_code < 0))
>
>             return ret_code;
>
>       if (mtd->ecc_strength == 0)
>
>             return 0;   /* device lacks ecc */
>
>       return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0; }
>
>
>
> So if the bitflips num over mtd->bitflip_threshold the mtd_read_oob 
> will return -EUCLEAN and tags->ecc_result > YAFFS_ECC_RESULT_NO_ERROR.
>
> Then we will call yaffs_handle_chunk_error.
>
> void yaffs_handle_chunk_error(struct yaffs_dev *dev,
>
>                         struct yaffs_block_info *bi)
>
> {
>
>       if (!bi->gc_prioritise) {
>
>             bi->gc_prioritise = 1;
>
>             dev->has_pending_prioritised_gc = 1;
>
>             bi->chunk_error_strikes++;
>
>
>
>             if (bi->chunk_error_strikes > 3) {
>
>                   bi->needs_retiring = 1; /* Too many stikes, so 
> retire */
>
>                   yaffs_trace(YAFFS_TRACE_ALWAYS,
>
>                         "yaffs: Block struck out");
>
>
>
>             }
>
>       }
>
> }
>
>
>
> From the code we can see if bitflips num over mtd->bitflip_threshold 
> we will mark this block as gc if bitflips num over 
> mtd->bitflip_threshold over three times we will mark this block as bad block.
>
>
>
> We define bad block is if erase or program failed we can mark this 
> block as bad block.
>
> So is it reasonable just according to the bitflips over
> mtd->bitflip_threshold over three times to judge the block as bad block?
>
> What's your opinion about my doubts?