linux-kernel - Re: [PATCH net-next v6 5/9] net: dsa: microchip: ksz9477: Add Wake on Magic Packet support

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Message-ID: <20231020082934.teh24h557qox5hna@skbuf>
Date:   Fri, 20 Oct 2023 11:29:34 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        Conor Dooley <conor+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        UNGLinuxDriver@...rochip.com,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v6 5/9] net: dsa: microchip: ksz9477: Add Wake
 on Magic Packet support

On Fri, Oct 20, 2023 at 11:23:50AM +0300, Vladimir Oltean wrote:
> On Fri, Oct 20, 2023 at 07:08:56AM +0200, Oleksij Rempel wrote:
> > On Thu, Oct 19, 2023 at 08:29:53PM +0300, Vladimir Oltean wrote:
> > > I don't get it, why do you release the reference on the MAC address as
> > > soon as you successfully get it? Without a reference held, the
> > > programmed address still lingers on, but the HSR offload code, on a
> > > different port with a different MAC address, can change it and break WoL.
> > 
> > It is ksz9477_get_wol() function. We do not actually need to program
> > here the MAC address, we only need to test if we would be able to get
> > it. To show the use more or less correct information on WoL
> > capabilities. For example, instead showing the user that Wake on Magic
> > is supported, where we already know that is not the case, we can already
> > show correct information. May be it will be better to have
> > extra option for ksz_switch_macaddr_get() to not allocate and do the
> > refcounting or have a separate function.
> 
> Ah, yes, it is from get_wol(). Maybe a ksz_switch_macaddr_tryget(ds, port)
> which returns bool (true if dev->switch_macaddr is NULL, or if non-NULL
> and ether_addr_equal(dev->switch_macaddr->addr, port addr))?

Hmm, I've checked other uses of the "tryget" name in the kernel and
their semantics all seem to imply that upon success, a reference is
acquired. That would not be the case here, so the naming would be
confusing. How about a bool ksz_switch_macaddr_check(ds, port)?