Re: [PATCH v8 00/13] Adds support for PHY LEDs with offload triggers

[Andrew Lunn]

On Fri, Mar 10, 2023 at 10:37:25AM +0100, Linus Walleij wrote:
> On Thu, Mar 9, 2023 at 4:22 PM Andrew Lunn <andrew@xxxxxxx> wrote:
> 
> > As to 'how a certain trigger on a certain LED is going to associate
> > itself with, say, a certain port' is clearly a property of the
> > hardware, when offloading is supported. I've not seen a switch you can
> > arbitrarily assign LEDs to ports. The Marvell switches have the LED
> > registers within the port registers, for example, two LEDs per port.
> 
> Aha so there is an implicit HW dependency between the port and the
> LED, that we just cannot see in the device tree. Okay, it makes sense.

Well, i would say the dependency is in the device tree, in that the
LEDs are described in the ports, not as a block of their own at a
higher level within the switch. And in some switches, they might
actually be a block of registers in there own space, rather than in
the port registers. But i still expect there is a fixed mapping
between LED and port.

> I think there will be a day when a switch without LED controller appears,
> but the system has a few LEDs for the ports connected to an
> arbitrary GPIO controller, and then we will need this. But we have
> not seen that yet :)

The microchip sparx5 might be going in that direction. It has what
looks like a reasonably generic sgpio controller:
drivers/pinctrl/pinctrl-microchip-sgpio.c

But this not just about switches. It is also plain NICs. And using
ledtrig-netdev, you could make your keyboard LED blink based on
network traffic etc. So yes, using a phandle to an LED could very well
be useful in the future.

   Andrew