netdev - Re: [PATCH net-next v2 3/3] net: ethtool: Remove PHYLIB direct dependency

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Date:   Mon, 6 Jul 2020 11:40:00 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Michal Kubecek <mkubecek@...e.cz>,
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH net-next v2 3/3] net: ethtool: Remove PHYLIB direct
 dependency

On Sun,  5 Jul 2020 21:27:58 -0700 Florian Fainelli wrote:
> +	ops = ethtool_phy_ops;
> +	if (!ops || !ops->start_cable_test) {

nit: don't think member-by-member checking is necessary. We don't
expect there to be any alternative versions of the ops, right?

> +		ret = -EOPNOTSUPP;
> +		goto out_rtnl;
> +	}
> +
>  	ret = ethnl_ops_begin(dev);
>  	if (ret < 0)
>  		goto out_rtnl;
>  
> -	ret = phy_start_cable_test(dev->phydev, info->extack);
> +	ret = ops->start_cable_test(dev->phydev, info->extack);

nit: my personal preference would be to hide checking the ops and
calling the member in a static inline helper.

Note that we should be able to remove this from phy.h now:

#if IS_ENABLED(CONFIG_PHYLIB)
int phy_start_cable_test(struct phy_device *phydev,
			 struct netlink_ext_ack *extack);
int phy_start_cable_test_tdr(struct phy_device *phydev,
			     struct netlink_ext_ack *extack,
			     const struct phy_tdr_config *config);
#else
static inline
int phy_start_cable_test(struct phy_device *phydev,
			 struct netlink_ext_ack *extack)
{
	NL_SET_ERR_MSG(extack, "Kernel not compiled with PHYLIB support");
	return -EOPNOTSUPP;
}
static inline
int phy_start_cable_test_tdr(struct phy_device *phydev,
			     struct netlink_ext_ack *extack,
			     const struct phy_tdr_config *config)
{
	NL_SET_ERR_MSG(extack, "Kernel not compiled with PHYLIB support");
	return -EOPNOTSUPP;
}
#endif


We could even risk a direct call:

#if IS_REACHABLE(CONFIG_PHYLIB)
static inline int do_x()
{
	return __do_x();
}
#else
static inline int do_x()
{
	if (!ops)
		return -EOPNOTSUPP;
	return ops->do_x();
}
#endif

But that's perhaps doing too much...