netdev - Re: [PATCH v1 1/3] dt-bindings: net: dsa: microchip: add microchip,single-led-mode flag

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Message-ID: <9090d12e-e85e-4827-9dc3-5bbece12c50d@twx-software.de>
Date: Wed, 28 Jan 2026 16:10:41 +0100
From: Heinrich Töws (TWx) <ht@...-software.de>
To: Andrew Lunn <andrew@...n.ch>
Cc: netdev@...r.kernel.org, f.fainelli@...il.com, olteanv@...il.com,
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org
Subject: Re: [PATCH v1 1/3] dt-bindings: net: dsa: microchip: add
 microchip,single-led-mode flag

Hi Andrew,

Am 28.01.26 um 14:59 schrieb Andrew Lunn:
> Are there other blinking modes? If the LED is capable of more, you
> should be using /sys/class/leds and the netdev trigger. If the only
> thing it can indicate is link and activity, this approach is O.K.

I re-checked the datasheet (DS00002392). The KSZ9477 PHY ports indeed 
have two pins, but they are not general-purpose. The term "programmable" 
in the datasheet refers only to switching between two fixed 
hardware-mapped modes via MMD:

1. Tri-Color Dual-LED Mode (Default): The pins LEDx_1 and LEDx_0 work in 
conjunction to indicate link speed (10/100/1000) and activity. For 
example, 10BASE-T status is indicated by both pins working together.

2. Single-LED Mode: Here, the logic is simplified so that LEDx_1 
indicates Link and LEDx_0 indicates Activity.

There is no "Manual Mode" or "GPIO Mode" for these pins. They are driven 
by a fixed internal state machine. Since we cannot control the pins' 
brightness or trigger events independently from the PHY's hardcoded 
logic, the netdev trigger or the LED class cannot be used to emulate 
this behavior.

> Is there a dual LED mode? Triple LED mode? What happens if this
> property is not found?

If the property is not found, the switch remains in its default 
"Tri-Color Dual-LED Mode".

I will clarify this in the description for v2.

Thanks,Heinrich.