Date:   Fri, 3 Feb 2023 09:17:06 +0100
From:   Simon Horman <simon.horman@corigine.com>
To:     netdev@kapio-technology.com
Cc:     davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
        Florian Fainelli <f.fainelli@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vladimir Oltean <olteanv@gmail.com>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Kurt Kanzenbach <kurt@linutronix.de>,
        Hauke Mehrtens <hauke@hauke-m.de>,
        Woojung Huh <woojung.huh@microchip.com>,
        "maintainer:MICROCHIP KSZ SERIES ETHERNET SWITCH DRIVER" 
        <UNGLinuxDriver@microchip.com>, Sean Wang <sean.wang@mediatek.com>,
        Landen Chao <Landen.Chao@mediatek.com>,
        DENG Qingfang <dqfext@gmail.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Claudiu Manoil <claudiu.manoil@nxp.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        =?utf-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= <clement.leger@bootlin.com>,
        Jiri Pirko <jiri@resnulli.us>,
        Ivan Vecera <ivecera@redhat.com>,
        Roopa Prabhu <roopa@nvidia.com>,
        Nikolay Aleksandrov <razor@blackwall.org>,
        Russell King <linux@armlinux.org.uk>,
        Christian Marangi <ansuelsmth@gmail.com>,
        open list <linux-kernel@vger.kernel.org>,
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        <linux-arm-kernel@lists.infradead.org>,
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        <linux-mediatek@lists.infradead.org>,
        "open list:RENESAS RZ/N1 A5PSW SWITCH DRIVER" 
        <linux-renesas-soc@vger.kernel.org>,
        "moderated list:ETHERNET BRIDGE" <bridge@lists.linux-foundation.org>
Subject: Re: [PATCH net-next 3/5] drivers: net: dsa: add fdb entry flags
 incoming to switchcore drivers
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On Thu, Feb 02, 2023 at 05:45:56PM +0100, netdev@kapio-technology.com wrote:
> On 2023-01-31 19:54, Simon Horman wrote:
> > > --- a/drivers/net/dsa/b53/b53_common.c
> > > +++ b/drivers/net/dsa/b53/b53_common.c
> > > @@ -1684,11 +1684,15 @@ static int b53_arl_op(struct b53_device
> > > *dev, int op, int port,
> > > 
> > >  int b53_fdb_add(struct dsa_switch *ds, int port,
> > >  		const unsigned char *addr, u16 vid,
> > > -		struct dsa_db db)
> > > +		u16 fdb_flags, struct dsa_db db)
> > >  {
> > >  	struct b53_device *priv = ds->priv;
> > >  	int ret;
> > > 
> > > +	/* Ignore entries with set flags */
> > > +	if (fdb_flags)
> > > +		return 0;
> > 
> > 
> > 	Would returning -EOPNOTSUPP be more appropriate?
> > 
> > ...
> 
> I don't think that would be so good, as the command
> 
> bridge fdb replace ADDR dev <DEV> master dynamic
> 
> is a valid command and should not generate errors. When ignored by the
> driver, it will just install a dynamic FDB entry in the bridge, and the
> bridge will age it.

Sure, I agree that it's not necessarily an error that needs
to propagate to the user.

My assumption, which I now see is likely false, is that drivers
could return -EOPNOTSUPP, to indicate to higher layers that the operation
is not supported. But the higher layers may not propagate that.

But it seems that is not the case here. So I think return 0 is fine
after all. Sorry for the noise.