linux-kernel - Re: [PATCH -next] net: stmmac: platform: remove useless if/else

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Date:   Thu, 29 Oct 2020 13:34:45 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Zou Wei <zou_wei@...wei.com>
Cc:     peppe.cavallaro@...com, alexandre.torgue@...com,
        joabreu@...opsys.com, davem@...emloft.net, kuba@...nel.org,
        mcoquelin.stm32@...il.com, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] net: stmmac: platform: remove useless if/else

On Thu, Oct 29, 2020 at 10:33:52AM +0800, Zou Wei wrote:
> Fix the following coccinelle report:
> 
> ./drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c:233:6-8:
> WARNING: possible condition with no effect (if == else)
> 
> Both branches are the same, so remove the else if/else altogether.
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Zou Wei <zou_wei@...wei.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index af34a4c..f6c69d0 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -230,8 +230,6 @@ static int stmmac_mtl_setup(struct platform_device *pdev,
>  		plat->tx_sched_algorithm = MTL_TX_ALGORITHM_WFQ;
>  	else if (of_property_read_bool(tx_node, "snps,tx-sched-dwrr"))
>  		plat->tx_sched_algorithm = MTL_TX_ALGORITHM_DWRR;
> -	else if (of_property_read_bool(tx_node, "snps,tx-sched-sp"))
> -		plat->tx_sched_algorithm = MTL_TX_ALGORITHM_SP;
>  	else
>  		plat->tx_sched_algorithm = MTL_TX_ALGORITHM_SP;

I actually prefer the original code. Code is also documentation. It
documents the fact, if "snps,tx-sched-sp" is in device tree, we use
MTL_TX_ALGORITHM_SP, but otherwise we default to MTL_TX_ALGORITHM_SP.

As with my suggestion for forcedeth, i would move the default setting
to before the whole if/else if/else block to document it is the
default.

Or just consider this a false positive and leave it alone. I can see
value in the coccinelle script, but it is going to have a lot of false
positive cases, so i'm not sure there is value in working around them
all.

	Andrew