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

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Date:   Mon, 6 Jul 2020 11:45:38 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
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>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2 3/3] net: ethtool: Remove PHYLIB direct
 dependency



On 7/6/2020 11:40 AM, Jakub Kicinski wrote:
> 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?

There could be, a network device driver not using PHYLIB could register
its own operations and only implement a subset of these operations.

> 
>> +		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:

I would prefer to keep thsose around in case a network device driver
cannot punt entirely onto PHYLIB and instead needs to wrap those calls
around.

> 
> #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...

Fine either way with me, let us see what Michal and Andrew think about that.
-- 
Florian