linux-kernel - Re: [PATCH net-next 2/4] net: dsa: Add wrappers for overloaded ndo

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Date:   Sun, 19 Jul 2020 09:10:41 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Taehee Yoo <ap420073@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Maxim Mikityanskiy <maximmi@...lanox.com>,
        Richard Cochran <richardcochran@...il.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 2/4] net: dsa: Add wrappers for overloaded
 ndo_ops



On 7/19/2020 8:40 AM, Andrew Lunn wrote:
>> +#if IS_ENABLED(CONFIG_NET_DSA)
>> +#define dsa_build_ndo_op(name, arg1_type, arg1_name, arg2_type, arg2_name) \
>> +static int inline dsa_##name(struct net_device *dev, arg1_type arg1_name, \
>> +			     arg2_type arg2_name)	\
>> +{							\
>> +	const struct dsa_netdevice_ops *ops;		\
>> +	int err = -EOPNOTSUPP;				\
>> +							\
>> +	if (!dev->dsa_ptr)				\
>> +		return err;				\
>> +							\
>> +	ops = dev->dsa_ptr->netdev_ops;			\
>> +	if (!ops || !ops->name)				\
>> +		return err;				\
>> +							\
>> +	return ops->name(dev, arg1_name, arg2_name);	\
>> +}
>> +#else
>> +#define dsa_build_ndo_op(name, ...)			\
>> +static inline int dsa_##name(struct net_device *dev, ...) \
>> +{							\
>> +	return -EOPNOTSUPP;				\
>> +}
>> +#endif
>> +
>> +dsa_build_ndo_op(ndo_do_ioctl, struct ifreq *, ifr, int, cmd);
>> +dsa_build_ndo_op(ndo_get_phys_port_name, char *, name, size_t, len);
> 
> Hi Florian
> 
> I tend to avoid this sort of macro magic. Tools like
> https://elixir.bootlin.com/ and other cross references have trouble
> following it. The current macros only handle calls with two
> parameters. And i doubt it is actually saving many lines of code, if
> there are only two invocations.

It saves about 20 lines of code for each new function that is added.
Since the boilerplate logic is always the same, if you prefer I could
provide it as a separate helper function and avoid the macro to generate
the function body, yes let's do that.
-- 
Florian