netdev - Re: stmmac: pci: Add dwmac support for Loongson

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Date:   Tue, 22 Jun 2021 10:17:14 +0800
From:   zhangqing <zhangqing@...ngson.cn>
To:     Colin Ian King <colin.king@...onical.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: stmmac: pci: Add dwmac support for Loongson



On 06/21/2021 11:51 PM, Colin Ian King wrote:
> Hi,
>
> Static analysis by Coverity on today's linux-next has found an issue in
> function loongson_dwmac_probe with the following commit:
>
> commit 30bba69d7db40e732d6c0aa6d4890c60d717e314
> Author: Qing Zhang <zhangqing@...ngson.cn>
> Date:   Fri Jun 18 10:53:34 2021 +0800
>
>      stmmac: pci: Add dwmac support for Loongson
>
> The analysis is as follows:
>
> 110        plat->phy_interface = device_get_phy_mode(&pdev->dev);
>
> Enum compared against 0
> (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an
> unsigned value is never true. plat->phy_interface < 0U.
>
> 111        if (plat->phy_interface < 0)
> 112                dev_err(&pdev->dev, "phy_mode not found\n");
>
> Enum plat->phy_interface is unsigned, so can't be negative and so the
> comparison will always be false.

Hi，Colin

Thanks for your advice,

I see this judgment in stmmac_platform.c:

plat->phy_interface = device_get_phy_mode(&pdev->dev);
if (plat->phy_interface < 0)
return ERR_PTR(plat->phy_interface);

plat->interface = stmmac_of_get_mac_mode(np);
if (plat->interface < 0)

>
> A possible fix is to use int variable ret for the assignment and check:
>
>
>          ret = device_get_phy_mode(&pdev->dev);
>          if (ret < 0)
>                  dev_err(&pdev->dev, "phy_mode not found\n");
>          plat->phy_interface = ret;
>
> ..however, I think the dev_err may need handling too, e.g.
>
>          ret = device_get_phy_mode(&pdev->dev);
>          if (ret < 0) {
>                  dev_err(&pdev->dev, "phy_mode not found\n");
> 		ret = -ENODEV;
> 		goto cleanup;		/* needs to be written */
> 	}
>          plat->phy_interface = ret;
>
> Colin
looks ok, but can be written to use of_get_phy_mode() , like this:

phy_interface_t interface;
ret = of_get_phy_mode(pdev->dev->of_node, &interface);
if (ret)
        return -EINVAL;


plat_dat->interface = interface;
if(!plat->interface)
dev_err(&pdev->dev, "Unsupported interface mode: %s",
         phy_modes(plat->interface));

Thanks

-Qing