Re: [PATCH V4] leds: trigger: Introduce an USB port trigger

From: Pavel Machek
Date: Mon Oct 10 2016 - 10:34:05 EST


> This commit adds a new trigger responsible for turning on LED when USB
> device gets connected to the specified USB port. This can can useful for
> various home routers that have USB port(s) and a proper LED telling user
> a device is connected.
> The trigger gets its documentation file but basically it just requires
> specifying USB port in a Linux format (e.g. echo 1-1 > new_port).
> During work on this trigger there was a plan to add DT bindings for it,
> but there wasn't an agreement on the format yet. This can be worked on
> later, a sysfs interface is needed anyway for platforms not using DT.
> Another planned feature is support for LED reacting to the USB activity.
> This can be implemented with another sysfs file for setting mode. The
> default mode wouldn't change so there won't be ABI breakage and such
> feature can be safely implemented later.

Actually... USB device plugs/unplugs are pretty rare events... Can we
just do this in userspace using udevd?

(cesky, pictures)

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