linux-kernel - Re: [PATCH net-next v4 8/8] net: dsa: felix: Add support for MRP

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Message-ID: <20210217102448.oea5dwl2qnhybir3@skbuf>
Date:   Wed, 17 Feb 2021 10:24:49 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "ivecera@...hat.com" <ivecera@...hat.com>,
        "nikolay@...dia.com" <nikolay@...dia.com>,
        "roopa@...dia.com" <roopa@...dia.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "vivien.didelot@...il.com" <vivien.didelot@...il.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "rasmus.villemoes@...vas.dk" <rasmus.villemoes@...vas.dk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bridge@...ts.linux-foundation.org" 
        <bridge@...ts.linux-foundation.org>
Subject: Re: [PATCH net-next v4 8/8] net: dsa: felix: Add support for MRP

On Tue, Feb 16, 2021 at 10:42:05PM +0100, Horatiu Vultur wrote:
> @@ -112,6 +113,7 @@ static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
>  	ocelot_xfh_get_qos_class(extraction, &qos_class);
>  	ocelot_xfh_get_tag_type(extraction, &tag_type);
>  	ocelot_xfh_get_vlan_tci(extraction, &vlan_tci);
> +	ocelot_xfh_get_cpuq(extraction, &cpuq);
>  
>  	skb->dev = dsa_master_find_slave(netdev, 0, src_port);
>  	if (!skb->dev)
> @@ -126,6 +128,12 @@ static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
>  	skb->offload_fwd_mark = 1;
>  	skb->priority = qos_class;
>  
> +#if IS_ENABLED(CONFIG_BRIDGE_MRP)
> +	if (eth_hdr(skb)->h_proto == cpu_to_be16(ETH_P_MRP) &&
> +	    cpuq & BIT(OCELOT_MRP_CPUQ))

Checking the EtherType seems redundant, since those are the only frames
trapped to the MRP CPU queue.

Also, the cpuq variable is potentially unused when CONFIG_BRIDGE_MRP is
unset. I'm concerned that static analysis people may come in and try to
fix it up with even more ifdeffery, which is definitely not what I would
like to go for.

How about just the following, which is not conditionally compiled:
	if (!(cpuq & BIT(OCELOT_MRP_CPUQ)))
		skb->offload_fwd_mark = 1;

> +		skb->offload_fwd_mark = 0;
> +#endif
> +
>  	/* Ocelot switches copy frames unmodified to the CPU. However, it is
>  	 * possible for the user to request a VLAN modification through
>  	 * VCAP_IS1_ACT_VID_REPLACE_ENA. In this case, what will happen is that
> -- 
> 2.27.0
>