linux-kernel - Re: [PATCH 1/2] mt76: mt7915: fix unused 'mode' variable

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Date:   Thu, 25 Feb 2021 10:58:36 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Felix Fietkau <nbd@....name>,
        Lorenzo Bianconi <lorenzo.bianconi83@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Shayne Chen <shayne.chen@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH 1/2] mt76: mt7915: fix unused 'mode' variable

On Thu, Feb 25, 2021 at 03:59:14PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> clang points out a possible corner case in the mt7915_tm_set_tx_cont()
> function if called with invalid arguments:
> 
> drivers/net/wireless/mediatek/mt76/mt7915/testmode.c:593:2: warning: variable 'mode' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
>         default:
>         ^~~~~~~
> drivers/net/wireless/mediatek/mt76/mt7915/testmode.c:597:13: note: uninitialized use occurs here
>         rateval =  mode << 6 | rate_idx;
>                    ^~~~
> drivers/net/wireless/mediatek/mt76/mt7915/testmode.c:506:37: note: initialize the variable 'mode' to silence this warning
>         u8 rate_idx = td->tx_rate_idx, mode;
>                                            ^
> 
> Change it to return an error instead of continuing with invalid data
> here.
> 
> Fixes: 3f0caa3cbf94 ("mt76: mt7915: add support for continuous tx in testmode")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/wireless/mediatek/mt76/mt7915/testmode.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/testmode.c b/drivers/net/wireless/mediatek/mt76/mt7915/testmode.c
> index 7fb2170a9561..aa629e1fb420 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7915/testmode.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/testmode.c
> @@ -543,6 +543,7 @@ mt7915_tm_set_tx_cont(struct mt7915_phy *phy, bool en)
>  		tx_cont->bw = CMD_CBW_20MHZ;
>  		break;
>  	default:
> +		return -EINVAL;

Remove the break if we are adding a return?

>  		break;
>  	}
>  
> @@ -591,6 +592,7 @@ mt7915_tm_set_tx_cont(struct mt7915_phy *phy, bool en)
>  		mode = MT_PHY_TYPE_HE_MU;
>  		break;
>  	default:
> +		return -EINVAL;
>  		break;
>  	}
>  
> -- 
> 2.29.2
>