Re: [RFC PATCH 1/9] leds: Load trigger modules on-demand if used as hw control trigger

[Andrew Lunn]

On Sat, Feb 28, 2026 at 03:05:58AM +0800, Rong Zhang wrote:
> In the following patches, we are about to support hardware initiated
> trigger transitions to/from the device's hw control trigger. In case
> the LED hardware switches itself to hw control mode, hw control trigger
> must be loaded before so that the transition can be processed.

This sounds backwards around.

A Linux LED starts out life as a dumb LED. You can set its brightness
using /sys/class/leds/<foo>/brightness.

Userspace policy can then give additional meaning to the LED. It could
blink a heartbeat, disk activity, show rf-kill status, activity on a
serial port, what link speed eth42 has etc. The general design in
Linux is that any LED can be used for any of these functions. You
decide what an LED should indicate by selecting the trigger for it. To
be able to select the trigger, the trigger needs to be already loaded.

Only once you have the trigger load, and the LED using the trigger,
then you can think about can the trigger be offloaded to hardware.

In linux, policy is in user space. If policy says led X is to be used
with trigger Y, user space can get the needed trigger module loaded.

     Andrew