A question about nand_read()

Patrick Turley patrick.turley at freescale.com
Tue Nov 18 19:43:55 EST 2008

My tree is up-to-date as I'm writing this message.

I'm looking at nand_read() in nand_base.c, starting at line 1175, quoted  
here for your convenience:

static int nand_read(struct mtd_info *mtd, loff_t from, size_t len,
                      size_t *retlen, uint8_t *buf)
         struct nand_chip *chip = mtd->priv;
         int ret;

         /* Do not allow reads past end of device */
         if ((from + len) > mtd->size)
                 return -EINVAL;
         if (!len)
                 return 0;

         nand_get_device(chip, mtd, FL_READING);

         chip->ops.len = len;
         chip->ops.datbuf = buf;
         chip->ops.oobbuf = NULL;

         ret = nand_do_read_ops(mtd, from, &chip->ops);

         *retlen = chip->ops.retlen;


         return ret;

In particular, I'm looking at the preparation to call nand_do_read_ops(),  
where the chip->ops structure is filled in.

Here's a small excerpt from nand_do_read_ops() that concerns me:

     /* Now read the page into the buffer */
     if (unlikely(ops->mode == MTD_OOB_RAW))
             ret = chip->ecc.read_page_raw(mtd, chip, bufpoi);
     else if (!aligned && NAND_SUBPAGE_READ(chip) && !oob)
             ret = chip->ecc.read_subpage(mtd, chip, col, bytes, bufpoi);
             ret = chip->ecc.read_page(mtd, chip, bufpoi);
     if (ret < 0)

Note that nand_do_read_ops() will look at the mode field of the ops  
structure, but this field hasn't been set by nand_read().

On the face of it, this looks like a bug. Is there something I don't know  
that makes this not a bug? For example, is the value in the mode field  
intended to persist across operations?

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