linux-kernel - Re: [PATCH v4 7/7] mtd: spi-nor: add read loop

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Date:	Fri, 14 Aug 2015 12:08:00 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Andrew Murray <amurray@...edded-bits.co.uk>
Cc:	Hou Zhiqiang <B48286@...escale.com>,
	Huang Shijie <shijie.huang@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Han Xu <han.xu@...escale.com>,
	Rafał Miłecki <zajec5@...il.com>,
	Huang Shijie <b32955@...escale.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Marek Vasut <marex@...x.de>, Gabor Juhos <juhosg@...nwrt.org>,
	Bean Huo 霍斌斌, <beanhuo@...ron.com>,
	MTD Maling List <linux-mtd@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 7/7] mtd: spi-nor: add read loop

On 14 August 2015 at 12:02, Andrew Murray <amurray@...edded-bits.co.uk> wrote:
> On 14 August 2015 at 10:23, Michal Suchanek <hramrach@...il.com> wrote:
>> mtdblock and ubi do not handle the situation when read returns less data
>> than requested. Loop in spi-nor until buffer is filled or an error is
>> returned.
>>
>> Signed-off-by: Michal Suchanek <hramrach@...il.com>
>> ---
>>  drivers/mtd/spi-nor/spi-nor.c | 20 ++++++++++++++------
>>  1 file changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index e0ae9cf..246fac7 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -738,14 +738,22 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
>>         if (ret)
>>                 return ret;
>>
>> -       ret = nor->read(nor, from, len, buf);
>> +       while (len) {
>> +               ret = nor->read(nor, from, len, buf);
>> +               if (ret <= 0)
>> +                       goto read_err;
>> +
>> +               BUG_ON(ret > len);
>> +               *retlen += ret;
>
> Is *retlen initialized to 0 anywhere?

It's initialized in mtdcore and passed into mtd->_read.

Yes, the interface is really awkward.

int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
             u_char *buf)
{
        int ret_code;
        *retlen = 0;


Thanks

Michal
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