netdev - Re: [PATCH][next] can: kvaser_pciefd: remove redundant negative check on trigger

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Message-ID: <0d61d4a1-4307-af0e-5dae-517dea89c992@canonical.com>
Date:   Thu, 25 Jul 2019 13:41:04 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     wharms@....de
Cc:     Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] can: kvaser_pciefd: remove redundant negative check
 on trigger

On 25/07/2019 13:37, walter harms wrote:
> 
> 
> Am 25.07.2019 13:25, schrieb Colin King:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> The check to see if trigger is less than zero is always false, trigger
>> is always in the range 0..255.  Hence the check is redundant and can
>> be removed.
>>
>> Addresses-Coverity: ("Logically dead code")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  drivers/net/can/kvaser_pciefd.c | 3 ---
>>  1 file changed, 3 deletions(-)
>>
>> diff --git a/drivers/net/can/kvaser_pciefd.c b/drivers/net/can/kvaser_pciefd.c
>> index 3af747cbbde4..68e00aad0810 100644
>> --- a/drivers/net/can/kvaser_pciefd.c
>> +++ b/drivers/net/can/kvaser_pciefd.c
>> @@ -652,9 +652,6 @@ static void kvaser_pciefd_pwm_stop(struct kvaser_pciefd_can *can)
>>  	top = (pwm_ctrl >> KVASER_PCIEFD_KCAN_PWM_TOP_SHIFT) & 0xff;
>>  
>>  	trigger = (100 * top + 50) / 100;
>> -	if (trigger < 0)
>> -		trigger = 0;
>> -
> 	to be fair i do not understand the calculation here here.
> 	(100*top+50)/100 = top+50/100
> 
> 	but seems to be int so it should be =top

Indeed it does not do anything, that does look like an unintentional
bug. Good catch.

> 
> 	did i missunderstand something here ?
> 
> 	re,
> 	 wh
> 
> 
>>  	pwm_ctrl = trigger & 0xff;
>>  	pwm_ctrl |= (top & 0xff) << KVASER_PCIEFD_KCAN_PWM_TOP_SHIFT;
>>  	iowrite32(pwm_ctrl, can->reg_base + KVASER_PCIEFD_KCAN_PWM_REG);