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

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

[Ivan Safonov]

((thermometer < 0) ? 0 : (thermometer == X)) and (thermometer == X) are equal for X >= 0.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
---
 drivers/net/wireless/ath/ath9k/ar9003_eeprom.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c b/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
index 8b4561e..35e57f7 100644
--- a/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
+++ b/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
@@ -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;
 	REG_RMW_FIELD(ah, AR_PHY_65NM_CH0_RXTX4,
 		      AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
 	if (pCap->chip_chainmask & BIT(1)) {
-		therm_on = (thermometer < 0) ? 0 : (thermometer == 1);
+		therm_on = thermometer == 1;
 		REG_RMW_FIELD(ah, AR_PHY_65NM_CH1_RXTX4,
 			      AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
 	}
 	if (pCap->chip_chainmask & BIT(2)) {
-		therm_on = (thermometer < 0) ? 0 : (thermometer == 2);
+		therm_on = thermometer == 2;
 		REG_RMW_FIELD(ah, AR_PHY_65NM_CH2_RXTX4,
 			      AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
 	}
-- 
2.4.10

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

[Joe Perches]

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

> Signed-off-by: Ivan Safonov <insafonov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  drivers/net/wireless/ath/ath9k/ar9003_eeprom.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c b/drivers/net/wireless/ath/ath9k/ar9003_eeprom.c
[]
> @@ -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.

>  	REG_RMW_FIELD(ah, AR_PHY_65NM_CH0_RXTX4,
>  		      AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
>  	if (pCap->chip_chainmask & BIT(1)) {
> -		therm_on = (thermometer < 0) ? 0 : (thermometer == 1);
> +		therm_on = thermometer == 1;
>  		REG_RMW_FIELD(ah, AR_PHY_65NM_CH1_RXTX4,
>  			      AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
>  	}
>  	if (pCap->chip_chainmask & BIT(2)) {
> -		therm_on = (thermometer < 0) ? 0 : (thermometer == 2);
> +		therm_on = thermometer == 2;
>  		REG_RMW_FIELD(ah, AR_PHY_65NM_CH2_RXTX4,
>  			      AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
>  	}

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

[Ivan Safonov]

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).

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

[Joe Perches]

On Tue, 2015-12-29 at 01:38 +0700, Ivan Safonov wrote:
> 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}.

Looks like it can be -1 to me (range: -1, 0, 1, 2)

static int ar9003_hw_get_thermometer(struct ath_hw *ah)
{
	struct ar9300_eeprom *eep = &ah->eeprom.ar9300_eep;
	struct ar9300_base_eep_hdr *pBase = &eep->baseEepHeader;
	int thermometer =  (pBase->miscConfiguration >> 1) & 0x3;

	return --thermometer;
}

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

[Ivan Safonov]

On 12/29/2015 07:31 AM, Joe Perches wrote:
> On Tue, 2015-12-29 at 01:38 +0700, Ivan Safonov wrote:
>> 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}.
> Looks like it can be -1 to me (range: -1, 0, 1, 2)
>
> static int ar9003_hw_get_thermometer(struct ath_hw *ah)
> {
> 	struct ar9300_eeprom *eep = &ah->eeprom.ar9300_eep;
> 	struct ar9300_base_eep_hdr *pBase = &eep->baseEepHeader;
> 	int thermometer =  (pBase->miscConfiguration >> 1) & 0x3;
>
> 	return --thermometer;
> }

X is not thermometer. The thermometer is {-1, 0, 1, 2}. X is {0, 1, 2}.
All possible X valueswritten in the comments:

ar9003_hw_get_thermometer used only in ar9003_hw_thermometer_apply:

     static void ar9003_hw_thermometer_apply(struct ath_hw *ah)
     {
         struct ath9k_hw_capabilities *pCap = &ah->caps;
         int thermometer = ar9003_hw_get_thermometer(ah);
         u8 therm_on = (thermometer < 0) ? 0 : 1;

         REG_RMW_FIELD(ah, AR_PHY_65NM_CH0_RXTX4,
                   AR_PHY_65NM_CH0_RXTX4_THERM_ON_OVR, therm_on);
         if (pCap->chip_chainmask & BIT(1))
             REG_RMW_FIELD(ah, AR_PHY_65NM_CH1_RXTX4,
                       AR_PHY_65NM_CH0_RXTX4_THERM_ON_OVR, therm_on);
         if (pCap->chip_chainmask & BIT(2))
             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); /* X = 0 */
         REG_RMW_FIELD(ah, AR_PHY_65NM_CH0_RXTX4,
                   AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
         if (pCap->chip_chainmask & BIT(1)) {
             therm_on = (thermometer < 0) ? 0 : (thermometer == 1);    
/* X = 1 */
             REG_RMW_FIELD(ah, AR_PHY_65NM_CH1_RXTX4,
                       AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
         }
         if (pCap->chip_chainmask & BIT(2)) {
             therm_on = (thermometer < 0) ? 0 : (thermometer == 2);    
/* X = 2 */
             REG_RMW_FIELD(ah, AR_PHY_65NM_CH2_RXTX4,
                       AR_PHY_65NM_CH0_RXTX4_THERM_ON, therm_on);
         }
     }

There is no X = -1.