linux-kernel - Re: [net-next RFC PATCH 0/6] Add support for qca8k mdio rw in Ethernet packet

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Message-ID: <61afff9e.1c69fb81.92f07.6e7d@mx.google.com>
Date:   Wed, 8 Dec 2021 01:42:59 +0100
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [net-next RFC PATCH 0/6] Add support for qca8k mdio rw in
 Ethernet packet

On Wed, Dec 08, 2021 at 02:40:51AM +0200, Vladimir Oltean wrote:
> On Wed, Dec 08, 2021 at 02:04:32AM +0200, Vladimir Oltean wrote:
> > On Wed, Dec 08, 2021 at 01:47:36AM +0200, Vladimir Oltean wrote:
> > > > 2) is harder. But as far as i know, we have an 1:N setup.  One switch
> > > > driver can use N tag drivers. So we need the switch driver to be sure
> > > > the tag driver is what it expects. We keep the shared state in the tag
> > > > driver, so it always has valid data, but when the switch driver wants
> > > > to get a pointer to it, it needs to pass a enum dsa_tag_protocol and
> > > > if it does not match, the core should return -EINVAL or similar.
> > > 
> > > In my proposal, the tagger will allocate the memory from its side of the
> > > ->connect() call. So regardless of whether the switch driver side
> > > connects or not, the memory inside dp->priv is there for the tagger to
> > > use. The switch can access it or it can ignore it.
> > 
> > I don't think I actually said something useful here.
> > 
> > The goal would be to minimize use of dp->priv inside the switch driver,
> > outside of the actual ->connect() / ->disconnect() calls.
> > For example, in the felix driver which supports two tagging protocol
> > drivers, I think these two methods would be enough, and they would
> > replace the current felix_port_setup_tagger_data() and
> > felix_port_teardown_tagger_data() calls.
> > 
> > An additional benefit would be that in ->connect() and ->disconnect() we
> > get the actual tagging protocol in use. Currently the felix driver lacks
> > there, because felix_port_setup_tagger_data() just sets dp->priv up
> > unconditionally for the ocelot-8021q tagging protocol (luckily the
> > normal ocelot tagger doesn't need dp->priv).
> > 
> > In sja1105 the story is a bit longer, but I believe that can also be
> > cleaned up to stay within the confines of ->connect()/->disconnect().
> > 
> > So I guess we just need to be careful and push back against dubious use
> > during review.
> 
> I've started working on a prototype for converting sja1105 to this model.
> It should be clearer to me by tomorrow whether there is anything missing
> from this proposal.

I'm working on your suggestion and I should be able to post another RFC
this night if all works correctly with my switch.

-- 
	Ansuel