netdev - Re: [PATCH] net: tulip: remove redundant assignment to variable new

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Date:   Mon, 24 Jan 2022 10:30:38 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Colin Ian King <colin.i.king@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-parisc@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: tulip: remove redundant assignment to variable
 new_csr6

On Sun, 23 Jan 2022 18:34:40 +0000 Colin Ian King wrote:
> Variable new_csr6 is being initialized with a value that is never
> read, it is being re-assigned later on. The assignment is redundant
> and can be removed.

> @@ -21,7 +21,7 @@ void pnic_do_nway(struct net_device *dev)
>  	struct tulip_private *tp = netdev_priv(dev);
>  	void __iomem *ioaddr = tp->base_addr;
>  	u32 phy_reg = ioread32(ioaddr + 0xB8);
> -	u32 new_csr6 = tp->csr6 & ~0x40C40200;
> +	u32 new_csr6;
>  
>  	if (phy_reg & 0x78000000) { /* Ignore baseT4 */
>  		if (phy_reg & 0x20000000)		dev->if_port = 5;

I can't say I see what you mean, it's not set in some cases:

			if (tp->medialock) {
			} else if (tp->nwayset  &&  (dev->if_port & 1)) {
				next_tick = 1*HZ;
			} else if (dev->if_port == 0) {
				dev->if_port = 3;
				iowrite32(0x33, ioaddr + CSR12);
				new_csr6 = 0x01860000;
				iowrite32(0x1F868, ioaddr + 0xB8);
			} else {
				dev->if_port = 0;
				iowrite32(0x32, ioaddr + CSR12);
				new_csr6 = 0x00420000;
				iowrite32(0x1F078, ioaddr + 0xB8);
			}
			if (tp->csr6 != new_csr6) {
				tp->csr6 = new_csr6;


That said clang doesn't complain so maybe I'm missing something static
analysis had figured out about this code.