A question about nand_read()

[Patrick Turley]

Fair enough. I'll check it out.


On Mon, 24 Nov 2008 03:53:05 -0600, Adrian Hunter  
<ext-adrian.hunter at nokia.com> wrote:

> Patrick Turley wrote:
>> No love? Is my question too n00bish?
>
> People are busy.
>
> You should test this yourself, and if you can make it go wrong
> submit a patch.
>
> I glanced at the code and it looks OK because struct nand_chip
> is always initialised to zero and chip->ops.mode is never assigned.
>
>> On Tue, 18 Nov 2008 18:43:55 -0600, Patrick Turley   
>> <patrick.turley at freescale.com> wrote:
>>
>>> 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;
>>>
>>>          nand_release_device(mtd);
>>>
>>>          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);
>>>      else
>>>              ret = chip->ecc.read_page(mtd, chip, bufpoi);
>>>      if (ret < 0)
>>>              break;
>>>
>>>
>>> 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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>