Hi Boris,
2017-06-13 17:30 GMT+09:00 Boris Brezillon <boris.brezil...@free-electrons.com>:
> On Tue, 13 Jun 2017 17:17:41 +0900
> Masahiro Yamada <yamada.masah...@socionext.com> wrote:
>
>> Hi Boris,
>>
>>
>> 2017-06-13 16:02 GMT+09:00 Boris Brezillon
>> <boris.brezil...@free-electrons.com>:
>>
>> >
>> > BTW, I also implemented ->read/write_buf_word() since the core may one
>> > day call these functions, and the default implementations used by the
>> > core when these hooks are NULL are not appropriate in your case.
>> >
>>
>> BTW, why doesn't the default hook in the core do like this?
>>
>>
>> static uint8_t nand_read_byte(struct mtd_info *mtd)
>> {
>> struct nand_chip *chip = mtd_to_nand(mtd);
>> uint8_t byte;
>>
>> chip->read_buf(chip, &byte, 1);
>> return byte;
>> }
>>
>>
>> ->read_byte() is a special case of ->read_buf() with length==1,
>> so this should work.
>
> Not sure it works for all implementation. ->read_byte() is expected
> to return the lower 8 bits when interacting with a 16-bits bus. If we do
> what you suggest, and ->read_buf() appears to be caching data in an
> intermediate buffer if the amount of data is not aligned on 2 bytes,
> you might retrieve data you don't care about when ->read_byte() is
> called several times.
You are right.
I missed the case where ->read_byte() is called repeatedly.
Thanks!
--
Best Regards
Masahiro Yamada
