linux-kernel - Re: staging: comedi: non working tests on unsigned cmd->convert

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Date:	Thu, 23 Apr 2009 11:53:57 +0100
From:	Ian Abbott <abbotti@....co.uk>
To:	Roel Kluin <roel.kluin@...il.com>
CC:	Greg KH <greg@...ah.com>,
	"fmhess@...rs.sourceforge.net" <fmhess@...rs.sourceforge.net>,
	Greg KH <gregkh@...e.de>, lkml <linux-kernel@...r.kernel.org>,
	Ian Abbott <ian.abbott@....co.uk>,
	David Schleef <ds@...leef.org>
Subject: Re: staging: comedi: non working tests on unsigned cmd->convert_arg

Roel Kluin wrote:
> Greg KH wrote:
>> On Wed, Apr 22, 2009 at 02:11:10PM -0400, Frank Mori Hess wrote:
>>> On Wednesday 22 April 2009, Greg KH wrote:
>>>> On Tue, Apr 21, 2009 at 03:18:10PM +0200, Roel Kluin wrote:
>>>>> vi drivers/staging/comedi/comedi.h +342
>>>>>
>>>>> and note that cmd->convert_arg in s626_ai_cmdtest() is unsigned.
>>>>> Should there maybe be a test:
>>>>>
>>>>> if (cmd->convert_src == TRIG_EXT && cmd->convert_arg > MAX)
>>>>>
>>>>> (and what should MAX be then?)
>>>> I don't know.  Let's ask the comedi developers :)
>>>>
>>>> Frank, what do you think about this?
>>> It looks like there already is such a test, right below the useless one the 
>>> patch removes.
>> Ok, thanks for checking.  Roel, care to resend these patches then?
>>
>> thanks,
>>
>> greg k-h
>>
> So you don't want to set cmd->*_arg to 0 when beyond 39 or below 0?

Well setting cmd->*_arg to 0 when beyond 39 would be a change of
functionality, so that's a no-no for a cleanup patch.  And it would
never be below 0 because it's unsigned, so those 'if' statements in the
original were redundant.

> ------------------------------>8-------------8<---------------------------------
> Remove tests for negative unsigned.
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com> 
> ---
> diff --git a/drivers/staging/comedi/drivers/s626.c b/drivers/staging/comedi/drivers/s626.c
> index 30dec9d..a48b244 100644
> --- a/drivers/staging/comedi/drivers/s626.c
> +++ b/drivers/staging/comedi/drivers/s626.c
> @@ -1886,31 +1886,16 @@ static int s626_ai_cmdtest(struct comedi_device *dev, struct comedi_subdevice *s
>  		err++;
>  	}
>  
> -	if (cmd->start_src == TRIG_EXT && cmd->start_arg < 0) {
> -		cmd->start_arg = 0;
> -		err++;
> -	}
> -
>  	if (cmd->start_src == TRIG_EXT && cmd->start_arg > 39) {
>  		cmd->start_arg = 39;
>  		err++;
>  	}
>  
> -	if (cmd->scan_begin_src == TRIG_EXT && cmd->scan_begin_arg < 0) {
> -		cmd->scan_begin_arg = 0;
> -		err++;
> -	}
> -
>  	if (cmd->scan_begin_src == TRIG_EXT && cmd->scan_begin_arg > 39) {
>  		cmd->scan_begin_arg = 39;
>  		err++;
>  	}
>  
> -	if (cmd->convert_src == TRIG_EXT && cmd->convert_arg < 0) {
> -		cmd->convert_arg = 0;
> -		err++;
> -	}
> -
>  	if (cmd->convert_src == TRIG_EXT && cmd->convert_arg > 39) {
>  		cmd->convert_arg = 39;
>  		err++;


-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk>             )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587              )=-

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