linux-kernel - Re: [RESEND][PATCH] mtd: devices: m25p80: add support for mmap read request

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Date:	Wed, 18 May 2016 11:49:53 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Vignesh R <vigneshr@...com>
Cc:	Brian Norris <computersforpeace@...il.com>,
	MTD Maling List <linux-mtd@...ts.infradead.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND][PATCH] mtd: devices: m25p80: add support for mmap read request

On 18 May 2016 at 11:39, Vignesh R <vigneshr@...com> wrote:
> Hi,
>
> On 05/18/2016 02:53 PM, Michal Suchanek wrote:
>> Hello,
> [...]
>>>
>>> diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
>>> index c9c3b7fa3051..7730e633d7d3 100644
>>> --- a/drivers/mtd/devices/m25p80.c
>>> +++ b/drivers/mtd/devices/m25p80.c
>>> @@ -131,6 +131,26 @@ static int m25p80_read(struct spi_nor *nor, loff_t from, size_t len,
>>>         /* convert the dummy cycles to the number of bytes */
>>>         dummy /= 8;
>>>
>>> +       if (spi_flash_read_supported(spi)) {
>>> +               struct spi_flash_read_message msg;
>>> +               int ret;
>>> +
>>> +               msg.buf = buf;
>>> +               msg.from = from;
>>> +               msg.len = len;
>>> +               msg.read_opcode = nor->read_opcode;
>>> +               msg.addr_width = nor->addr_width;
>>> +               msg.dummy_bytes = dummy;
>>> +               /* TODO: Support other combinations */
>>> +               msg.opcode_nbits = SPI_NBITS_SINGLE;
>>> +               msg.addr_nbits = SPI_NBITS_SINGLE;
>>> +               msg.data_nbits = m25p80_rx_nbits(nor);
>>> +
>>> +               ret = spi_flash_read(spi, &msg);
>>> +               *retlen = msg.retlen;
>>
>> This is wrong. The previous retlen is never passed into msg so it must
>> be added and not assigned as is seen a few lines below:
>>
>>         ret = m.actual_length - m25p_cmdsz(nor) - dummy;
>>         if (ret < 0)
>>                 return -EIO;
>>         *retlen += ret;
>>
>> This interface with odd design and poor documentation will be
>> hopefully weeded out with
>> mtd: spi-nor: stop passing around retlen
>> so there is probably no need to patch this separately.
>>
>
> This patch was applied by Brian quite sometime back and the v7  of "mtd:
> spi-nor: stop passing around retlen" patch takes care of removing the
> offending code: https://lkml.org/lkml/2016/5/5/692
>

Yes, I am looking exactly at that patchset but don't see it applied
anywhere yet.

Thanks

Michal