From:   Hans Schultz <netdev@kapio-technology.com>
To:     Simon Horman <simon.horman@corigine.com>
Cc:     Vladimir Oltean <olteanv@gmail.com>, davem@davemloft.net,
        kuba@kernel.org, netdev@vger.kernel.org,
        Florian Fainelli <f.fainelli@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        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?Q?Cl=C3=A9ment_L=C3=A9ger?= <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>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@lists.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <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 5/5] net: dsa: mv88e6xxx: implementation of
 dynamic ATU entries
In-Reply-To: <Y+EkiAyexZrPoCpP@corigine.com>
References: <20230130173429.3577450-1-netdev@kapio-technology.com>
 <20230130173429.3577450-6-netdev@kapio-technology.com>
 <Y9lkXlyXg1d1D0j3@corigine.com>
 <9b12275969a204739ccfab972d90f20f@kapio-technology.com>
 <Y9zDxlwSn1EfCTba@corigine.com> <20230203204422.4wrhyathxfhj6hdt@skbuf>
 <Y94TebdRQRHMMj/c@corigine.com>
 <4abbe32d007240b9c3aea9c8ca936fa3@kapio-technology.com>
 <Y+EkiAyexZrPoCpP@corigine.com>
Date:   Tue, 14 Feb 2023 22:14:55 +0100
Message-ID: <87fsb83q5s.fsf@kapio-technology.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Mon, Feb 06, 2023 at 17:02, Simon Horman <simon.horman@corigine.com> wrote:
>
> Just to clarify my suggestion one last time, it would be along the lines
> of the following (completely untested!). I feel that it robustly covers
> all cases for fdb_flags. And as a bonus doesn't need to be modified
> if other (unsupported) flags are added in future.
>
> 	if (fdb_flags & ~(DSA_FDB_FLAG_DYNAMIC))
> 		return -EOPNOTSUPP;
>
> 	is_dynamic = !!(fdb_flags & DSA_FDB_FLAG_DYNAMIC)
> 	if (is_dynamic)
> 		state = MV88E6XXX_G1_ATU_DATA_STATE_UC_AGE_7_NEWEST;
>
>
> And perhaps for other drivers:
>
> 	if (fdb_flags & ~(DSA_FDB_FLAG_DYNAMIC))
> 		return -EOPNOTSUPP;
> 	if (fdb_flags)
> 		return 0;
>
> Perhaps a helper would be warranted for the above.

How would such a helper look? Inline function is not clean.

>
> But in writing this I think that, perhaps drivers could return -EOPNOTSUPP
> for the DSA_FDB_FLAG_DYNAMIC case and the caller can handle, rather tha
> propagate, -EOPNOTSUPP.

I looked at that, but changing the caller is also a bit ugly.

>
> Returning -EOPNOTSUPP is the normal way to drivers to respond to requests
> for unsupported hardware offloads. Sticking to that may be clearner
> in the long run. That said, I do agree your current patch is correct
> given the flag that is defined (by your patchset).