linux-kernel - Re: [PATCH net-next 0/2] net: dsa: don't unmask port bitmaps

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Message-ID: <20171024092234.GA2911@lunn.ch>
Date:   Tue, 24 Oct 2017 11:22:34 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next 0/2] net: dsa: don't unmask port bitmaps

> In case of probe deferral, you get the full probe function to exit with
> an error, and that usually involves freeing the recently allocated
> dsa_switch instance, and then allocating a new one when probe is
> re-entered, so that should not be a problem.

Hi Florian

That is the simple case. I remember having problems with more complex
cases, D in DSA. Switches 1 and 2 probe O.K, switch 3 fail with
EPROBE_DEFER. Switch 3, as you say, releases its dsa_switch instance,
so will get a freshly zero'ed new instance when it probes
again. However, switches 1 and 2 only experience the unwind at the DSA
level. The devices are not removed and later probed again. They have a
'dirty' dsa_switch structure the next time they are applied.

I just think there might be potential for regressions here. But i've
not yet looked at the details to really know if there actually is.

    Andrew