Re: Changing LEDs status in response to Power Events

[Patrick Williams <patrick@stwcx.xyz>]

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On Wed, Jan 06, 2021 at 04:52:32PM -0800, Maxim Sloyko wrote:
> Hi all,
> 
> We would like to change the state of some of the LEDs in response to some
> power events. For example, if the system goes from Standby to On, the LED
> needs to change from blinking fast to blinking slowly.  The way we are
> doing it right now is we have a script that runs every second, polls system
> state over D-Bus (xyz.openbmc_project.State.Chassis and
> xyz.openbmc_project.State.Host) and then, again over D-Bus, ask
> phosphor-led-manager to switch LED into a new state. This does not sound
> like a good solution to me, so I have a few questions:
> 
> 0. Did I miss some existing way to do it in OpenBMC?
> 1. If not, does anybody have the same problem and how do you solve this?
> 2. If not, Is anybody working on a solution for this?
> 3. If not, any thoughts on what's the best way to handle this? I can see at
> least two approaches:
>    a) Implement some callbacks in x86-power-control, so that one can
> register their services/targets to be notified of the event.
>    b) Implement this in phosphor-led-manager, so that it can listen to
> D-Bus events and respond to them.

This usecase is one of the reasons phosphor-state-manager was
implemented using systemd targets (or at least one of the nice fallouts
of that design).  The intention was that system-specific things like
this could easily install themselves into dependencies on the state
transition targets.

Unfortunately, if you're using x86-power-control as your state-manager
I don't think you get this feature.

-- 
Patrick Williams

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