Subject: Re: [PATCH] /drivers/net/wireless/ath/ath9k remove unnecessary ?: operator

From: Ivan Safonov <[email-masked]>
Date: Tue, 29 Dec 2015 01:38:02 +0700

On 12/29/2015 12:56 AM, Joe Perches wrote:
> On Mon, 2015-12-28 at 20:48 +0700, Ivan Safonov wrote:
>> ((thermometer < 0) ? 0 : (thermometer == X)) and (thermometer == X) are equal for X >= 0.
> X is not guaranteed to be >= 0 here

X is fixed constant. In this case X is {0, 1, 2}.

>> @@ -4097,16 +4097,16 @@ static void ar9003_hw_thermometer_apply(struct ath_hw *ah)
>>   		REG_RMW_FIELD(ah, AR_PHY_65NM_CH2_RXTX4,
>>   			      AR_PHY_65NM_CH0_RXTX4_THERM_ON_OVR, therm_on);
>>   
>> -	therm_on = (thermometer < 0) ? 0 : (thermometer == 0);
>> +	therm_on = thermometer == 0;
> This code is not equivalent.
>
> Check what happens when thermometer is -1.

therm_on = (thermometer < 0) ? 0 : (thermometer == 0) =>
therm_on = (true) ? 0 : (thermometer == 0) =>

therm_on is 0

therm_on = thermometer == 0 =>

therm_on = false

false is equal to 0

Value of the thermometer variable isanerror code, or athermometercode. 
The thermometercode is never equal to the error code (thermometercode >= 
0, error code <0).