linux-kernel - Re: [PATCH][V2] drivers: thermal: processor_thermal

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Date:   Mon, 29 Jul 2019 14:34:35 +0200
From:   walter harms <wharms@....de>
To:     Colin King <colin.king@...onical.com>
CC:     Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        linux-pm@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V2] drivers: thermal: processor_thermal_device: fix missing
 bitwise-or operators



Am 29.07.2019 14:03, schrieb Colin King:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The variable val is having the top 8 bits cleared and then the variable is being
> re-assinged and setting just the top 8 bits.  I believe the intention was bitwise-or
> in the top 8 bits.  Fix this by replacing the = operators with &= and |= instead.
> 
> Addresses-Coverity: ("Unused value")
> Fixes: b0c74b08517e ("drivers: thermal: processor_thermal_device: Export sysfs inteface for TCC offset")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
> 
> V2: Add in &= operator missing from V1. Doh.
> 
> ---
>  .../thermal/intel/int340x_thermal/processor_thermal_device.c  | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/thermal/intel/int340x_thermal/processor_thermal_device.c b/drivers/thermal/intel/int340x_thermal/processor_thermal_device.c
> index 6f6ac6a8e82d..97333fc4be42 100644
> --- a/drivers/thermal/intel/int340x_thermal/processor_thermal_device.c
> +++ b/drivers/thermal/intel/int340x_thermal/processor_thermal_device.c
> @@ -163,8 +163,8 @@ static int tcc_offset_update(int tcc)
>  	if (err)
>  		return err;
>  
> -	val = ~GENMASK_ULL(31, 24);
> -	val = (tcc & 0xff) << 24;
> +	val &= ~GENMASK_ULL(31, 24);
> +	val |= (tcc & 0xff) << 24;
>  

IMHO GENMASK_ULL(31, 24) is a complicated way to say 0xFF000000
In this special case it would be better to use that (or 0xff<<24).

just my 2 cents,

re,
 wh


>  	err = wrmsrl_safe(MSR_IA32_TEMPERATURE_TARGET, val);
>  	if (err)