netdev - Re: [RFC PATCH 01/10] net: phy: Add driver for Loongson PHY

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Message-ID: <ZK+thg7xIKt7b8X+@shell.armlinux.org.uk>
Date: Thu, 13 Jul 2023 08:53:42 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Feiyang Chen <chenfeiyang@...ngson.cn>
Cc: andrew@...n.ch, hkallweit1@...il.com, peppe.cavallaro@...com,
	alexandre.torgue@...s.st.com, joabreu@...opsys.com,
	chenhuacai@...ngson.cn, dongbiao@...ngson.cn,
	loongson-kernel@...ts.loongnix.cn, netdev@...r.kernel.org,
	loongarch@...ts.linux.dev, chris.chenfeiyang@...il.com
Subject: Re: [RFC PATCH 01/10] net: phy: Add driver for Loongson PHY

On Thu, Jul 13, 2023 at 10:46:53AM +0800, Feiyang Chen wrote:
> +#define PHY_ID_LS7A2000		0x00061ce0
> +#define GNET_REV_LS7A2000	0x00
> +
> +static int ls7a2000_config_aneg(struct phy_device *phydev)
> +{
> +	if (phydev->speed == SPEED_1000)
> +		phydev->autoneg = AUTONEG_ENABLE;
> +
> +	if (linkmode_test_bit(ETHTOOL_LINK_MODE_10baseT_Full_BIT,
> +	    phydev->advertising) ||
> +	    linkmode_test_bit(ETHTOOL_LINK_MODE_100baseT_Full_BIT,
> +	    phydev->advertising) ||
> +	    linkmode_test_bit(ETHTOOL_LINK_MODE_1000baseT_Full_BIT,
> +	    phydev->advertising))
> +	    return genphy_config_aneg(phydev);

While it's fine to use four spaces within the if () expression, this
"return" should be indented with a tab.

> +
> +	netdev_info(phydev->attached_dev, "Parameter Setting Error\n");

Does this give the opportunity for userspace to spam the kernel log?
E.g. by a daemon repeatedly trying to set link parameters? Should it
be rate limited?

> +	return -1;

Sigh, not this laziness disease yet again. -1 is -EPERM. Return a
real errno code.

> +int ls7a2000_match_phy_device(struct phy_device *phydev)
> +{
> +	struct net_device *ndev;
> +	struct pci_dev *pdev;
> +
> +	if ((phydev->phy_id & 0xfffffff0) != PHY_ID_LS7A2000)
> +		return 0;

	if (!phy_id_compare(phydev->phy_id, PHY_ID_LS7A2000, 0xfffffff0))
		return 0;

> +
> +	ndev = phydev->mdio.bus->priv;

This doesn't look safe to me - you're assuming that if the PHY ID
above matches, that the MDIO bus' private data is something you know
which is far from guaranteed.

The mdio bus has a parent device - that would be a safer route to
check what the parent device is, provided the mdio bus is created so
that it's a child of the parent PCI device.

-- 
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