linux-kernel - Re: [PATCH v7 06/11] leds: trigger: netdev: add hardware control support

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Message-ID: <Y6LX43poXJ4k/7mv@shell.armlinux.org.uk>
Date:   Wed, 21 Dec 2022 09:54:43 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Christian Marangi <ansuelsmth@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>, Pavel Machek <pavel@....cz>,
        John Crispin <john@...ozen.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-leds@...r.kernel.org,
        Tim Harvey <tharvey@...eworks.com>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Subject: Re: [PATCH v7 06/11] leds: trigger: netdev: add hardware control
 support

On Wed, Dec 21, 2022 at 12:59:55AM +0100, Andrew Lunn wrote:
> > > One thought on this approach though - if one has a PHY that supports
> > > "activity" but not independent "rx" and "tx" activity indications
> > > and it doesn't support software control, how would one enable activity
> > > mode? There isn't a way to simultaneously enable both at the same
> > > time... However, I need to check whether there are any PHYs that fall
> > > into this category.
> > >
> > 
> > Problem is that for such feature and to have at least something working
> > we need to face compromise. We really can't support each switch feature
> > and have a generic API for everything.
> 
> I agree we need to make compromises. We cannot support every LED
> feature of every PHY, they are simply too diverse. Hopefully we can
> support some features of every PHY. In the worst case, a PHY simply
> cannot be controlled via this method, which is the current state
> today. So it is not worse off.

... and that compromise is that it's not going to be possible to enable
activity mode on 88e151x with how the code stands and with the
independent nature of "rx" and "tx" activity control currently in the
netdev trigger... making this whole approach somewhat useless for
Marvell PHYs.

We really need to see a working implementation for this code for more
than just one PHY to prove that it is actually possible for it to
support other PHYs. If not, it isn't actually solving the problem,
and we're going to continue getting custom implementations to configure
the LED settings.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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