linux-kernel - Re: [PATCH] ARM: dts: imx53: ppd: alarm LEDs use kernel LED interface

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Date:   Fri, 29 May 2020 20:03:06 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...labora.com,
        Ian Ray <ian.ray@...com>, Samu Nuutamo <samu.nuutamo@...cit.fi>
Subject: Re: [PATCH] ARM: dts: imx53: ppd: alarm LEDs use kernel LED interface

Hi,

On Fri, May 29, 2020 at 06:02:04PM +0200, Pavel Machek wrote:
> > ping?
> 
> Well, I thought that we maybe do not need standard LEDs on medical hardware.

The discussion died and the patch was not applied :) In general
IDK how worthwhile it is to use standard LED names for them. I
suppose the number of people planning to create something like
OpenWRT for medical devices is not so big.

> > On Fri, Apr 24, 2020 at 02:44:23PM +0200, Sebastian Reichel wrote:
> > > On Fri, Apr 24, 2020 at 11:32:26AM +0200, Pavel Machek wrote:
> > > > On Thu 2020-04-16 16:51:23, Sebastian Reichel wrote:
> > > > > From: Ian Ray <ian.ray@...com>
> > > > > 
> > > > > Use kernel LED interface for the alarm LEDs.
> > > > 
> > > > Could we get these changes cced to LED maintainers?
> > > 
> > > Sorry, you are not turning up via get_maintainer.pl and usually
> > > subsystem maintainers are not CC'd for every DT device instance.
> > > E.g. I do not want to be always CC'd for DT board file containing
> > > a battery/charger. I'm quite surprised you want to be CC'd for
> > > them, just looking at ARM DT files there are over 1000 instances
> > > of leds.
> 
> Well, we have mess in the naming; I'd like to clear it up.

I understand.

> > > > > +		alarm1 {
> > > > > +			label = "alarm:red";
> > > > > +			gpios = <&gpio7 3 GPIO_ACTIVE_HIGH>;
> > > > > +		};
> > > > 
> > > > So... What is function of these leds, and can we get naming more
> > > > consistent with rest of the kernel?
> > > 
> > > The device is a medical patient monitor and these are alarm LEDs
> > > informing about critical device or patient status. They are
> > > referenced by their color (those are discrete LEDs, not a
> > > multi-color one) basically everywhere. The only exception is
> > > "silenced", which means that audible alarm is surpressed. I
> > > don't think we have something comparable for any of those LEDs
> > > in the mainline tree.
> 
> Actually, we have "platform:*:mute" LEDs, that could be used for
> "silenced".

I see you point, but wonder if mute is the right choice. The LED
signals a silenced alarm, which IMHO is not the same:

* The alarm silencing is temporary and system unsilences after
  1-2 minutes.
* LED is usually blinking instead of solid like a laptop mute LED
  (so that operator is aware of silenced alarm)
* Device usually cannot be put into silenced mode before the alarm
  appears
* Some medical devices still generate perodic beeps

AFAIK this is named alarm silencing by basically everyone for
medical devices. So I think naming this platfrom:*:mute would
increase the mess.

-- Sebastian

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