netdev - Re: [RFC PATCH 11/16] net: dsa: Refactor selection of tag ops into a function

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Date:	Fri, 27 May 2016 15:35:57 -0400
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	Andrew Lunn <andrew@...n.ch>, netdev <netdev@...r.kernel.org>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	John Crispin <john@...ozen.org>, Bryan.Whitehead@...rochip.com,
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [RFC PATCH 11/16] net: dsa: Refactor selection of tag ops into a function

Hi Andrew,

Andrew Lunn <andrew@...n.ch> writes:

> @@ -26,6 +26,7 @@ enum dsa_tag_protocol {
>  	DSA_TAG_PROTO_TRAILER,
>  	DSA_TAG_PROTO_EDSA,
>  	DSA_TAG_PROTO_BRCM,
> +	_DSA_TAG_LAST,
>  };

I would avoid _ prefixed functions or symbols, we've seen in mv88e6xxx
that it doesn't make the code really readable.

There's already an implicit "DSA_TAG_PROTO" namespace, so I suggest
"DSA_MAX_TAGS" to keep it consistent with DSA_MAX_{PORTS,SWITCHES}.

[...]

> +	/*
> +	 * Tagging protocol operations for adding and removing an
> +	 * encapsulation tag.
> +	 */
> +	const struct dsa_device_ops *tag_ops;

dsa_device_ops seems too generic for the xmit/rcv tag-related pair. That
being said, I don't really have better suggestions. Any idea?

[...]

> +const struct dsa_device_ops *dsa_device_ops[_DSA_TAG_LAST] = {
> +#ifdef CONFIG_NET_DSA_TAG_DSA
> +	[DSA_TAG_PROTO_DSA] = &dsa_netdev_ops,
> +#endif
> +#ifdef CONFIG_NET_DSA_TAG_EDSA
> +	[DSA_TAG_PROTO_EDSA] = &edsa_netdev_ops,
> +#endif
> +#ifdef CONFIG_NET_DSA_TAG_TRAILER
> +	[DSA_TAG_PROTO_TRAILER] = &trailer_netdev_ops,
> +#endif
> +#ifdef CONFIG_NET_DSA_TAG_BRCM
> +	[DSA_TAG_PROTO_BRCM] = &brcm_netdev_ops,
> +#endif
> +	[DSA_TAG_PROTO_NONE] = &none_ops,
> +};
>  
>  /* switch driver registration ***********************************************/
>  static DEFINE_MUTEX(dsa_switch_drivers_mutex);
> @@ -225,6 +252,20 @@ static int dsa_cpu_dsa_setups(struct dsa_switch *ds, struct device *dev)
>  	return 0;
>  }
>  
> +const struct dsa_device_ops *dsa_resolve_tag_protocol(int tag_protocol)
> +{
> +	const struct dsa_device_ops *ops;
> +
> +	if (tag_protocol >= _DSA_TAG_LAST)
> +		return ERR_PTR(-EINVAL);
> +	ops = dsa_device_ops[tag_protocol];
> +
> +	if (!ops)
> +		return ERR_PTR(-ENOPROTOOPT);
> +
> +	return ops;
> +}

I don't see the need to add a dsa_device_ops array. I'd keep the switch
case on tag_protocol within this new dsa_resolve_tag_protocol function,
to make it more readable (no value checking necessary).

Thanks,

        Vivien