linux-kernel - Re: [PATCH 11/11] spi-dw: remove noop else clause

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Date:	Wed, 22 Jun 2011 20:13:45 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	Feng Tang <feng.tang@...el.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"spi-devel-general@...ts.sourceforge.net" 
	<spi-devel-general@...ts.sourceforge.net>
Subject: Re: [PATCH 11/11] spi-dw: remove noop else clause

On 06/22/2011 07:47 PM, Feng Tang wrote:
> On Thu, 23 Jun 2011 10:00:13 +0800
> "dirk.brandewie@...il.com"<dirk.brandewie@...il.com>  wrote:
>
>> From: Dirk Brandewie<dirk.brandewie@...il.com>
>>
>> The value of spi->bits_per_word is checked on function entry to be 8
>> or 16.  The else clause has no meaning since it can never be reached.
>>
>> Signed-off-by: Dirk Brandewie<dirk.brandewie@...il.com>
>> ---
>>   drivers/spi/spi-dw.c |    9 +++------
>>   1 files changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
>> index 7b3f607..5ddd45f 100644
>> --- a/drivers/spi/spi-dw.c
>> +++ b/drivers/spi/spi-dw.c
>> @@ -667,17 +667,14 @@ static int spi_dw_setup(struct spi_device *spi)
>>   		chip->enable_dma = chip_info->enable_dma;
>>   	}
>>
>> -	if (spi->bits_per_word<= 8) {
>> +	if (spi->bits_per_word == 8) {
>>   		chip->n_bytes = 1;
>>   		chip->dma_width = 1;
>> -	} else if (spi->bits_per_word<= 16) {
>> +	} else if (spi->bits_per_word == 16) {
>>   		chip->n_bytes = 2;
>>   		chip->dma_width = 2;
>> -	} else {
>> -		/* Never take>16b case for DW SPIC */
>> -		dev_err(&spi->dev, "invalid wordsize\n");
>> -		return -EINVAL;
>>   	}
>
> These "else" case is used to ban the slave spi devices which
> try to use 32 bits per word mode. This is like to tell those
> spi devices with 32 bpw capability "we don't support 32b, pls
> change"

The function has the prerequisite code:
	if (spi->bits_per_word != 8 && spi->bits_per_word != 16)
		return -EINVAL;

at the begining of the function so we will never be able to reach the else 
clause that is being removed.

>
>> +
>>   	chip->bits_per_word = spi->bits_per_word;
>>
>>   	chip->speed_hz = spi->max_speed_hz;

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