netdev - Re: [PATCH net-next 2/4] net: dsa: Link aggregation support

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Date:   Fri, 20 Nov 2020 01:30:09 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Tobias Waldekranz <tobias@...dekranz.com>
Cc:     davem@...emloft.net, kuba@...nel.org, vivien.didelot@...il.com,
        f.fainelli@...il.com, olteanv@...il.com, j.vosburgh@...il.com,
        vfalico@...il.com, andy@...yhouse.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/4] net: dsa: Link aggregation support

> +static struct dsa_lag *dsa_lag_get(struct dsa_switch_tree *dst,
> +				   struct net_device *dev)
> +{
> +	unsigned long busy = 0;
> +	struct dsa_lag *lag;
> +	int id;
> +
> +	list_for_each_entry(lag, &dst->lags, list) {
> +		set_bit(lag->id, &busy);
> +
> +		if (lag->dev == dev) {
> +			kref_get(&lag->refcount);
> +			return lag;
> +		}
> +	}
> +
> +	id = find_first_zero_bit(&busy, BITS_PER_LONG);
> +	if (id >= BITS_PER_LONG)
> +		return ERR_PTR(-ENOSPC);
> +
> +	lag = kzalloc(sizeof(*lag), GFP_KERNEL);
> +	if (!lag)
> +		return ERR_PTR(-ENOMEM);

Hi Tobias

My comment last time was to statically allocated them at probe
time. Worse case scenario is each port is alone in a LAG. Pointless,
but somebody could configure it. In dsa_tree_setup_switches() you can
count the number of ports and then allocate an array, or while setting
up a port, add one more lag to the list of lags.

   Andrew