linux-kernel - Re: [PATCH net v2 2/7] net: dsa: mt7530: fix trapping frames with multiple CPU ports on MT7530

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Date:   Tue, 13 Jun 2023 23:59:15 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Arınç ÜNAL <arinc.unal@...nc9.com>
Cc:     Daniel Golle <daniel@...rotopia.org>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Russell King <linux@...linux.org.uk>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Bartel Eerdekens <bartel.eerdekens@...stell8.be>,
        mithat.guner@...ont.com, erkin.bozoglu@...ont.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net v2 2/7] net: dsa: mt7530: fix trapping frames with
 multiple CPU ports on MT7530

On Tue, Jun 13, 2023 at 11:35:08PM +0300, Arınç ÜNAL wrote:
> On 13.06.2023 23:18, Vladimir Oltean wrote:
> > On Tue, Jun 13, 2023 at 08:58:33PM +0300, Arınç ÜNAL wrote:
> > > On 13.06.2023 20:39, Vladimir Oltean wrote:
> > > > Got it. Then this is really not a problem, and the commit message frames
> > > > it incorrectly.
> > > 
> > > Actually this patch fixes the issue it describes. At the state of this
> > > patch, when multiple CPU ports are defined, port 5 is the active CPU port,
> > > CPU_PORT bits are set to port 6.
> > > 
> > > Once "the patch that prefers port 6, I could easily find the exact name but
> > > your mail snipping makes it hard" is applied, this issue becomes redundant.
> > 
> > Ok. Well, you don't get bonus points for fixing a problem in 2 different
> > ways, once is enough :)
> 
> This is not the case here though.
> 
> This patch fixes an issue that can be stumbled upon in two ways. This is for
> when multiple CPU ports are defined on the devicetree.
> 
> As I explained to Russell, the first is the CPU_PORT field not matching the
> active CPU port.
> 
> The second is when port 5 becomes the only active CPU port. This can only
> happen with the changing the DSA conduit support.
> 
> The "prefer port 6" patch only prevents the first way from happening. The
> latter still can happen. But this feature doesn't exist yet. Hence why I
> think we should apply this series as-is (after some patch log changes) and
> backport it without this patch on kernels older than 5.18.
> 
> Arınç

I was following you until the last phrase. Why should we apply this series
as-is [ to net.git ], if this patch fixes a problem (the *only* problem in
lack of .port_change_master() support, aka for stable kernels) that is
already masked by a different patch targeted to net.git?