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

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Message-ID: <1451325412.3219.12.camel@perches.com>
Date:	Mon, 28 Dec 2015 09:56:52 -0800
From:	Joe Perches <joe@...ches.com>
To:	Ivan Safonov <insafonov@...il.com>,
	QCA ath9k Development <ath9k-devel@....qualcomm.com>
Cc:	Kalle Valo <kvalo@...eaurora.org>, linux-wireless@...r.kernel.org,
	ath9k-devel@...ts.ath9k.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] /drivers/net/wireless/ath/ath9k remove unnecessary ?:
 operator

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@...il.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
[]
> @@ -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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