linux-kernel - Re: [net-next PATCH 1/2] dt-bindings: Document QCA808x PHYs

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Message-ID: <2698eda5-af84-494f-844b-2ea87aa510d2@lunn.ch>
Date:   Mon, 11 Dec 2023 18:49:02 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Christian Marangi <ansuelsmth@...il.com>
Cc:     "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>,
        Conor Dooley <conor+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH 1/2] dt-bindings: Document QCA808x PHYs

On Mon, Dec 11, 2023 at 06:19:46PM +0100, Christian Marangi wrote:
> On Mon, Dec 11, 2023 at 04:54:12PM +0100, Andrew Lunn wrote:
> > > Mhhh with a generic property and LED core or phylib handling it... How
> > > it would work applying that setting on PHY side?
> > 
> > Add a .led_set_polarity callback to the PHY driver structure?
> > 
> > Take a look at other LED drivers. Does anything similar already exist?
> > It is unlikely that PHYs are the only sort of LED to have a polarity.
> >
> 
> Interesting topic... With a quick grep on Documentation for polarity of
> high, I can't find any use of it...

As i said, active-high is the default. So there is no need to specify
it. But if you look in Documentation/devicetree/binding/leds for
'active-low' you will find a few examples.

> Also main problem is that the thing is controlled globally and not per
> LED. (can be handled internally to the driver with some priv and check
> magic)

Ah, missed that. Marvell PHYs have polarity per LED.

It would be better to describe this correctly, so one property at a
higher level. We can then in the future add an 'active-low' property
per PHY.

> Is it worth to impemement the additional API to control this? And I
> guess a egenric binding should be added to ethernet-phy? Or should it be
> added to LEDs?

Since it is above individual LEDs, i would not add it to the generic
LED binding. But it could go inside the leds object of
ethernet-phy.yaml.

           leds {
                #address-cells = <1>;
                #size-cells = <0>;

		active-low;

                led@0 {
                    reg = <0>;
                    color = <LED_COLOR_ID_WHITE>;
                    function = LED_FUNCTION_LAN;
                    default-state = "keep";
                };

	Andrew