netdev - Re: [PATCH net-next v2 1/6] net: dcb: add new pcp selector to app object

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Message-ID: <YztdsF6b6SM9E5rw@DEN-LT-70577>
Date:   Mon, 3 Oct 2022 21:59:49 +0000
From:   <Daniel.Machon@...rochip.com>
To:     <kuba@...nel.org>
CC:     <petrm@...dia.com>, <netdev@...r.kernel.org>,
        <davem@...emloft.net>, <maxime.chevallier@...tlin.com>,
        <thomas.petazzoni@...tlin.com>, <edumazet@...gle.com>,
        <pabeni@...hat.com>, <Lars.Povlsen@...rochip.com>,
        <Steen.Hegelund@...rochip.com>, <UNGLinuxDriver@...rochip.com>,
        <joe@...ches.com>, <linux@...linux.org.uk>,
        <Horatiu.Vultur@...rochip.com>, <Julia.Lawall@...ia.fr>,
        <vladimir.oltean@....com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH net-next v2 1/6] net: dcb: add new pcp selector to app
 object

> On Mon, 3 Oct 2022 09:52:59 +0200 Petr Machata wrote:
> > I assumed the policy is much more strict with changes like this. If you
> > think it's OK, I'm fine with it as well.
> >
> > The userspace (lldpad in particular) is doing the opposite thing BTW:
> > assuming everything in the nest is a DCB_ATTR_IEEE_APP. When we start
> > emitting the new attribute, it will get confused.
> 
> Can you add an attribute or a flag to the request which would turn
> emitting the new attrs on?

As for this sparx5 impl. the new attrs or any other app attr, will not be
emitted by lldpad, since APP tx cannot be enabled when set/get_dcbx is not 
supported. IIUIC.

If lldpad was idd able to emit the new pcp app entries, they would be
emitted as invalid TLV's (assuming 255 or 24 selector value), because the
selector would be either zero or seven, which is currently not used for
any selector by the std. We then have time to patch lldpad to do whatever
with the new attr. Wouldn't this be acceptable?

As for iproute2/dcb, the new attr will just get ignored with a warning.