Re: [PATCH v2 4/6] net: ocelot: add support for ndo_change_mtu

From: "Clément Léger" <clement.leger@bootlin.com>
To: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	"UNGLinuxDriver@microchip.com" <UNGLinuxDriver@microchip.com>,
	Andrew Lunn <andrew@lunn.ch>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v2 4/6] net: ocelot: add support for ndo_change_mtu
Date: Wed, 3 Nov 2021 14:07:22 +0100	[thread overview]
Message-ID: <20211103140722.75a729e1@fixe.home> (raw)
In-Reply-To: <20211103124054.pcgruuipw5cpup6v@skbuf>

Le Wed, 3 Nov 2021 12:40:55 +0000,
Vladimir Oltean <vladimir.oltean@nxp.com> a écrit :

> > +static int ocelot_change_mtu(struct net_device *dev, int new_mtu)
> > +{
> > +	struct ocelot_port_private *priv = netdev_priv(dev);
> > +	struct ocelot_port *ocelot_port = &priv->port;
> > +	struct ocelot *ocelot = ocelot_port->ocelot;
> > +
> > +	ocelot_port_set_maxlen(ocelot, priv->chip_port, new_mtu);
> > +	WRITE_ONCE(dev->mtu, new_mtu);  
> 
> The WRITE_ONCE seems absolutely gratuitous to me.

I applied what is recommended in netdevice.h for the mtu field of the
netdev.
(https://elixir.bootlin.com/linux/v5.15/source/include/linux/netdevice.h#L1989)
And used in __dev_set_mtu
(https://elixir.bootlin.com/linux/v5.15/source/net/core/dev.c#L8849)

> 
> > +
> > +	return 0;
> > +}
> > +
> >  enum ocelot_action_type {
> >  	OCELOT_MACT_LEARN,
> >  	OCELOT_MACT_FORGET,

-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com