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

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Message-ID: <573C384F.8000209@ti.com>
Date:	Wed, 18 May 2016 15:09:27 +0530
From:	Vignesh R <vigneshr@...com>
To:	Michal Suchanek <hramrach@...il.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

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

-- 
Regards
Vignesh