Re: [PATCH v4 net-next 3/5] net: dsa: Link aggregation support

[Vladimir Oltean <olteanv@gmail.com>]

On Wed, Dec 16, 2020 at 05:00:54PM +0100, Tobias Waldekranz wrote:
> Monitor the following events and notify the driver when:
> 
> - A DSA port joins/leaves a LAG.
> - A LAG, made up of DSA ports, joins/leaves a bridge.
> - A DSA port in a LAG is enabled/disabled (enabled meaning
>   "distributing" in 802.3ad LACP terms).
> 
> When a LAG joins a bridge, the DSA subsystem will treat that as each
> individual port joining the bridge. The driver may look at the port's
> LAG device pointer to see if it is associated with any LAG, if that is
> required. This is analogue to how switchdev events are replicated out
> to all lower devices when reaching e.g. a LAG.
> 
> Drivers can optionally request that DSA maintain a linear mapping from
> a LAG ID to the corresponding netdev by setting ds->num_lag_ids to the
> desired size.
> 
> In the event that the hardware is not capable of offloading a
> particular LAG for any reason (the typical case being use of exotic
> modes like broadcast), DSA will take a hands-off approach, allowing
> the LAG to be formed as a pure software construct. This is reported
> back through the extended ACK, but is otherwise transparent to the
> user.
> 
> Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
> ---
> 
> I tried in vain to win checkpatch's approval of the foreach macros, no
> matter how many parentheses I added. Looking at existing macros, this
> style seems to be widely accepted. Is this a known issue?
> 
>  include/net/dsa.h  | 60 +++++++++++++++++++++++++++++++++++
>  net/dsa/dsa2.c     | 74 +++++++++++++++++++++++++++++++++++++++++++
>  net/dsa/dsa_priv.h | 36 +++++++++++++++++++++
>  net/dsa/port.c     | 79 ++++++++++++++++++++++++++++++++++++++++++++++
>  net/dsa/slave.c    | 70 ++++++++++++++++++++++++++++++++++++----
>  net/dsa/switch.c   | 50 +++++++++++++++++++++++++++++
>  6 files changed, 362 insertions(+), 7 deletions(-)
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index 4e60d2610f20..9092c711a37c 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -149,8 +149,41 @@ struct dsa_switch_tree {
>  
>  	/* List of DSA links composing the routing table */
>  	struct list_head rtable;
> +
> +	/* Maps offloaded LAG netdevs to a zero-based linear ID for
> +	 * drivers that need it.
> +	 */
> +	struct net_device **lags;
> +	unsigned int lags_len;
>  };
>  
> +#define dsa_lags_foreach_id(_id, _dst)				\
> +	for ((_id) = 0; (_id) < (_dst)->lags_len; (_id)++)	\
> +		if ((_dst)->lags[_id])
> +
> +#define dsa_lag_foreach_port(_dp, _dst, _lag)	       \
> +	list_for_each_entry(_dp, &(_dst)->ports, list) \
> +		if ((_dp)->lag_dev == (_lag))

ERROR: Macros with complex values should be enclosed in parentheses
#86: FILE: include/net/dsa.h:160:
+#define dsa_lags_foreach_id(_id, _dst)                         \
+       for ((_id) = 0; (_id) < (_dst)->lags_len; (_id)++)      \
+               if ((_dst)->lags[_id])
                                 ~~~
                                 missing parentheses

ERROR: Macros with complex values should be enclosed in parentheses
#90: FILE: include/net/dsa.h:164:
+#define dsa_lag_foreach_port(_dp, _dst, _lag)         \
+       list_for_each_entry(_dp, &(_dst)->ports, list) \
                            ~~~
                            missing parentheses
+               if ((_dp)->lag_dev == (_lag))