Re: [PATCH net-next] net: phy: bcm84881: add BCM84891/BCM84892 support

On Tue, Mar 24, 2026 at 08:18:21PM +0100, Andrew Lunn wrote:

quoted

In that case let me drop LEDs from v2 for now. The hardware is a single
bicolor LED (green/amber) with speed-based color selection (vendor firmware
does 10G=green, else amber). I don't immediately see an obvious way to express
that in the LED framework. If there's a good example to follow I'd appreciate
a pointer; otherwise I'll figure it out as a follow-up.

That is why asked about its capabilities.

The minimum you need for /sys/class/leds is to be able to turn the LED
on and off.

What sort of bicolor LED is it? 2 legs or three? Are green and amber
mutually exclusive, or can you control them independently? If they are
independent, then you can represent it as two LEDs. If the colours are
mutually exclusive its a different story.

Oh, unusual, there is a datasheet:

https://datasheet4u.com/pdf/1561522/BCM84891L.pdf

That is not like Broadcom.

That looks like 0x4011 isn't documented on this PHY.

There's also a bunch of MDIO commands that can be used to enquire the
status of USXGMII enable/AN enable, and what mode is used for 2.5G
and 5G.

It also states:

XFI/10GBASE-KR, USXGMII, 5000BASE-X, 2500BASE-X, 5000BASE-R, 2500BASE-R,
and 1000BASE-X (SGMII) MAC Interface

5G rate over USXGMII/XFI/5000BASE-R/5000BASE-X MAC interface

2.5G rate over USXGMII/XFI/2500BASE-R/2500BASE-X MAC interface

It doesn't say when SGMII mode is used (assuming it does support SGMII,
section 1.11 makes it very vague what is actually going on there - I
think someone was having a game of ethernet protocol bingo, finding out
how many different ethernet protocols they can state one after each
other in a single sentence, while making the sentence meaningless!)

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