linux-kernel - Re: [PATCH] net: dsa: Remove unsigned expression compared with zero

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Date:   Wed, 19 May 2021 21:24:00 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc:     andrew@...n.ch, vivien.didelot@...il.com, f.fainelli@...il.com,
        davem@...emloft.net, kuba@...nel.org, linux@...linux.org.uk,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: dsa: Remove unsigned expression compared with zero

Hi Jiapeng,

On Wed, May 19, 2021 at 06:49:51PM +0800, Jiapeng Chong wrote:
> Variable val is "u32" always >= 0, so val >= 0 condition are redundant.
> 
> Clean up the following coccicheck warning:
> 
> ./drivers/net/dsa/qca8k.c:732:5-8: WARNING: Unsigned expression compared
> with zero: val >= 0.
> 
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  drivers/net/dsa/qca8k.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index 4753228..7b38b8d 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -729,8 +729,7 @@
>  
>  	mutex_unlock(&bus->mdio_lock);
>  
> -	if (val >= 0)
> -		val &= QCA8K_MDIO_MASTER_DATA_MASK;
> +	val &= QCA8K_MDIO_MASTER_DATA_MASK;
>  
>  	return val;
>  }
> -- 
> 1.8.3.1
> 

The qca8k driver has some problems with the handling of signed/unsigned
return values. I would suggest a better approach to be to make
qca8k_mii_read32 to return an int value, and keep this check as is.