[RFC] mtd: Fix error code loss in mtdchar_read() function.

[ZhaoLong Wang]

> richard at nod.at wrote on Mon, 25 Sep 2023 16:59:31 +0200 (CEST):
>
>> ----- Ursprüngliche Mail -----
>>> Von: "Miquel Raynal" <miquel.raynal at bootlin.com>
>>>> Given this a second thought. I don't think a NAND driver is allowed to return
>>>> less than requests bytes and setting EBADMSG.
>>>> UBI's IO path has a comment on that:
>>>>
>>>>                  /*
>>>>                   * The driver should never return -EBADMSG if it failed to read
>>>>                   * all the requested data. But some buggy drivers might do
>>>>                   * this, so we change it to -EIO.
>>>>                   */
>>>>                  if (read != len && mtd_is_eccerr(err)) {
>>>>                          ubi_assert(0);
>>>>                          err = -EIO;
>>>>                  }
>>> Interesting. Shall we add this check to the mtd_read() path as well?
>>>
>>> Maybe with a WARN_ON()?
>> WARN_ON_ONCE(), please. But yes, let's add it.
> Zhaolong, can you take care of it?
>
>> Thanks,
>> //richard
>
> Thanks,
> Miquèl


Yes！That is a good idea, and I am pleased to do this.

Thanks,
Zhaolong