re: stmmac: pci: Add dwmac support for Loongson

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 [off-list ref]
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.

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