netdev - Re: [PATCH net-next 5/5] net: dsa: mv88e6xxx: implementation of dynamic ATU entries

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Date:   Tue, 14 Feb 2023 22:14:55 +0100
From:   Hans Schultz <netdev@...io-technology.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     Vladimir Oltean <olteanv@...il.com>, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        "maintainer:MICROCHIP KSZ SERIES ETHERNET SWITCH DRIVER" 
        <UNGLinuxDriver@...rochip.com>, Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Clément Léger <clement.leger@...tlin.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Russell King <linux@...linux.org.uk>,
        Christian Marangi <ansuelsmth@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:RENESAS RZ/N1 A5PSW SWITCH DRIVER" 
        <linux-renesas-soc@...r.kernel.org>,
        "moderated list:ETHERNET BRIDGE" <bridge@...ts.linux-foundation.org>
Subject: Re: [PATCH net-next 5/5] net: dsa: mv88e6xxx: implementation of
 dynamic ATU entries

On Mon, Feb 06, 2023 at 17:02, Simon Horman <simon.horman@...igine.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).