netdev - Re: [PATCH v2 net-next 1/8] net: dsa: Add helper to resolve bridge port from DSA port

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Date:   Thu, 18 Mar 2021 16:44:21 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Tobias Waldekranz <tobias@...dekranz.com>
Cc:     davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/8] net: dsa: Add helper to resolve bridge
 port from DSA port

On Thu, Mar 18, 2021 at 03:15:43PM +0100, Tobias Waldekranz wrote:
> In order for a driver to be able to query a bridge for information
> about itself, e.g. reading out port flags, it has to use a netdev that
> is known to the bridge. In the simple case, that is just the netdev
> representing the port, e.g. swp0 or swp1 in this example:
> 
>    br0
>    / \
> swp0 swp1
> 
> But in the case of an offloaded lag, this will be the bond or team
> interface, e.g. bond0 in this example:
> 
>      br0
>      /
>   bond0
>    / \
> swp0 swp1
> 
> Add a helper that hides some of this complexity from the
> drivers. Then, redefine dsa_port_offloads_bridge_port using the helper
> to avoid double accounting of the set of possible offloaded uppers.
> 
> Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
> ---
>  include/net/dsa.h  | 14 ++++++++++++++
>  net/dsa/dsa_priv.h | 14 +-------------
>  2 files changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index dac303edd33d..5c4340ecfeb2 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -493,6 +493,20 @@ static inline bool dsa_port_is_vlan_filtering(const struct dsa_port *dp)
>  		return dp->vlan_filtering;
>  }
>  
> +static inline
> +struct net_device *dsa_port_to_bridge_port(const struct dsa_port *dp)
> +{
> +	if (!dsa_is_user_port(dp->ds, dp->index))
> +		return NULL;
> +

According to my comment from 8/8, you could have replaced this here with

	if (!dp->bridge_dev)
		return NULL;

I think it's more intuitive to not return a bridge port if there isn't
any bridge to speak of. Whether you prefer to do that or not is up to
you, here's my review tag anyway.

Reviewed-by: Vladimir Oltean <olteanv@...il.com>

> +	if (dp->lag_dev)
> +		return dp->lag_dev;
> +	else if (dp->hsr_dev)
> +		return dp->hsr_dev;
> +
> +	return dp->slave;
> +}
> +
>  typedef int dsa_fdb_dump_cb_t(const unsigned char *addr, u16 vid,
>  			      bool is_static, void *data);
>  struct dsa_switch_ops {