netdev - Re: [PATCH v2 4/6] net: ocelot: add support for ndo_change

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Date:   Wed, 3 Nov 2021 14:07:22 +0100
From:   Clément Léger <clement.leger@...tlin.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 4/6] net: ocelot: add support for ndo_change_mtu

Le Wed, 3 Nov 2021 12:40:55 +0000,
Vladimir Oltean <vladimir.oltean@....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