netdev - Re: [net-next PATCH v4 02/14] net: dsa: qca8k: add LEDs basic support

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Date:   Fri, 17 Mar 2023 14:34:35 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Michal Kubiak <michal.kubiak@...el.com>
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>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        John Crispin <john@...ozen.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, Lee Jones <lee@...nel.org>,
        linux-leds@...r.kernel.org
Subject: Re: [net-next PATCH v4 02/14] net: dsa: qca8k: add LEDs basic support

> (I guess the LED configuration i only makes sense for non-CPU ports? It
> seems you want to configure up to 15 LEDs in total for 5 ports).

Hi Michal

In the general case, there is no reason that i can think that stops
the CPU port having LEDs. For many switch designs, there is no
specific CPU port, any can be used. And all ports are likely to have
an LED controller.

What becomes tricky with Linux is offloading blinking to CPU ports.
There is no netdev to represent it, hence no netdev based software
blinking. And without software blinking, you have nothing to offload
to hardware. But you could still use the LEDs for other things.

Having said all that, i don't think i have ever seen a box with LEDs
for the CPU port.

    Andrew