Re: [PATCH] net: ethernet: mtk_eth_soc: fix error checking in mtk_mac_config()

[Jakub Kicinski <kuba@kernel.org>]

On Sat,  8 Jan 2022 07:50:03 -0800 trix@redhat.com wrote:
> From: Tom Rix <trix@redhat.com>
> 
> Clang static analysis reports this problem
> mtk_eth_soc.c:394:7: warning: Branch condition evaluates
>   to a garbage value
>                 if (err)
>                     ^~~
> 
> err is not initialized and only conditionally set.
> Check err consistently with the rest of mtk_mac_config(),
> after even possible setting.
> 
> Fixes: 7e538372694b ("net: ethernet: mediatek: Re-add support SGMII")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index b67b4323cff08..a27e548488584 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -385,14 +385,16 @@ static void mtk_mac_config(struct phylink_config *config, unsigned int mode,
>  		       0 : mac->id;
>  
>  		/* Setup SGMIISYS with the determined property */
> -		if (state->interface != PHY_INTERFACE_MODE_SGMII)
> +		if (state->interface != PHY_INTERFACE_MODE_SGMII) {
>  			err = mtk_sgmii_setup_mode_force(eth->sgmii, sid,
>  							 state);
> -		else if (phylink_autoneg_inband(mode))
> +			if (err)
> +				goto init_err;
> +		} else if (phylink_autoneg_inband(mode)) {
>  			err = mtk_sgmii_setup_mode_an(eth->sgmii, sid);
> -
> -		if (err)
> -			goto init_err;
> +			if (err)
> +				goto init_err;
> +		}
>  
>  		regmap_update_bits(eth->ethsys, ETHSYS_SYSCFG0,
>  				   SYSCFG0_SGMII_MASK, val);

Why not init err to 0 before the if or add an else err = 0; branch?