linux-kernel - Re: [PATCH] staging: comedi: drivers: usbduxsigma: Removed variables that is never used

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Message-ID: <54CA68ED.3030806@berndporr.me.uk>
Date:	Thu, 29 Jan 2015 17:07:57 +0000
From:	Bernd Porr <mail@...ndporr.me.uk>
To:	Ian Abbott <abbotti@....co.uk>
CC:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Chase Southwood <chase.southwood@...il.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: comedi: drivers: usbduxsigma: Removed variables
 that is never used

Indeed. It can be completely removed. I was intending to speed up DIO 
reads during async acquisition but I decided against it because it would 
create unpredictable latencies.

Thanks Ian for flagging it!

/Bernd

Ian Abbott wrote:
> On 28/01/15 22:39, Rickard Strandqvist wrote:
>> Variable ar assigned a value that is never used.
>> I have also removed all the code that thereby serves no purpose.
>>
>> This was found using a static code analysis program called cppcheck
>>
>> Signed-off-by: Rickard Strandqvist 
>> <rickard_strandqvist@...ctrumdigital.se>
>> ---
>>   drivers/staging/comedi/drivers/usbduxsigma.c |    3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c 
>> b/drivers/staging/comedi/drivers/usbduxsigma.c
>> index dc19435..7b80887 100644
>> --- a/drivers/staging/comedi/drivers/usbduxsigma.c
>> +++ b/drivers/staging/comedi/drivers/usbduxsigma.c
>> @@ -215,7 +215,6 @@ static void usbduxsigma_ai_handle_urb(struct 
>> comedi_device *dev,
>>       struct usbduxsigma_private *devpriv = dev->private;
>>       struct comedi_async *async = s->async;
>>       struct comedi_cmd *cmd = &async->cmd;
>> -    unsigned int dio_state;
>>       uint32_t val;
>>       int ret;
>>       int i;
>> @@ -225,7 +224,7 @@ static void usbduxsigma_ai_handle_urb(struct 
>> comedi_device *dev,
>>           devpriv->ai_counter = devpriv->ai_timer;
>>
>>           /* get the state of the dio pins to allow external trigger */
>> -        dio_state = be32_to_cpu(devpriv->in_buf[0]);
>> +        be32_to_cpu(devpriv->in_buf[0]);
> 
> That line produces a compiler warning.  The line can be removed as the 
> call to be32_to_cpu() has no side-effects.  The "/* get the state ..." 
> comment line can also be removed as it is only associated with this line.
> 
> Perhaps Bernd intended to use dio_state for something here, but I'm not 
> sure what.
> 
>>
>>           /* get the data from the USB bus and hand it over to comedi */
>>           for (i = 0; i < cmd->chanlist_len; i++) {
>>
> 
> 

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