Re: [PATCH 04/24] dt-bindings: leds: Add function and color properties

From: Pavel Machek <pavel@ucw.cz>
To: Rob Herring <robh@kernel.org>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	Linux LED Subsystem <linux-leds@vger.kernel.org>,
	devicetree@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Baolin Wang <baolin.wang@linaro.org>,
	Daniel Mack <daniel@zonque.org>, Dan Murphy <dmurphy@ti.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Oleh Kravchenko <oleg@kaa.org.ua>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Simon Shields <simon@lineageos.org>
Subject: Re: [PATCH 04/24] dt-bindings: leds: Add function and color properties
Date: Wed, 12 Dec 2018 19:32:53 +0100	[thread overview]
Message-ID: <20181212183253.GA16578@amd> (raw)
In-Reply-To: <CAL_JsqJPMzwU9h2RSXeCfNTO5+zs7xTOb9jYcGivj+v_2RkG2A@mail.gmail.com>

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On Wed 2018-12-12 07:56:20, Rob Herring wrote:
> On Wed, Dec 12, 2018 at 3:59 AM Pavel Machek <pavel@ucw.cz> wrote:
> >
> > Hi!
> >
> > > > We would also probably need different DT properties for different
> > > > types of devices, since e.g. for network case the network interface
> > > > name would fit better for the LED name, than the phy name,
> > > > and we would need to know what type of device name we're going
> > > > to look for.
> > > >
> > > > Pavel gave following examples:
> > > >
> > > > eth0:green:link
> > > > adsl0:green:link
> > > > adsl0:red:error
> > > >
> > > > So we would have e.g.:
> > > >
> > > > associated-vl42-device = <&camera1>;
> > > > associated-network-device = <&phy1>;
> > > > associated-block-device = <&phy1>;
> > >
> > > Variable property names are kind of a pain to parse.
> > >
> > > Perhaps when LEDs are associated with a device, we shouldn't care
> > > within the context of the LED subsystem what the name is. The
> > > association is more important and if you have that exposed, then you
> > > don't really need to care what the name is. You still have to deal
> > > with a device with more than 1 LED, but that becomes a problem local
> > > to that device.
> > >
> > > What I'm getting at is following a more standard binding pattern of
> > > providers and consumers like we have for gpios, clocks, etc. So we'd
> > > have something like this:
> > >
> > > ethernet {
> > >   ...
> > >   leds = <&green_led>, <&red_led>;
> > >   led-names = "link", "err";
> > > };
> > >
> > > We can still support defining LED names as we've done, but we don't
> > > have to come up with some elaborate naming convention that covers
> > > every single case.
> >
> > I see that it would be more consistent with how gpios work, but I'm
> > afraid this does not fit LEDs properly.
> >
> > With power LED, you want to be able to say "this is just on". Some
> > poeple like heartbeat, and have LED for that. There may be LED for
> > "disk activity", meaning activity on any harddrive. And there may be
> > activity LED for specific disk.
> >
> > Only in the last case it would be suitable to have LED reference as a
> > child of an device...
> 
> Right. For all the other cases, why do you need any link with a
> device? What we have today is sufficient and can continue to be
> supported. A link to a device is only used if the led is associated
> with a particular device.

Right, so the link is only needed in some cases. So unlike your
example, we would have:

led1 { led-meaning = "heartbeat"; }
led2 { led-meaning = "link"; }
led3 { led-meaning = "err"; }
led4 { led-meaning = "activity"; what-activity = "all_harddisks"; }
ethernet { leds = < &led2, &led3 >; }

Dunno. I'd expect all the LED description in the LED node, not part of
the description there and back link from the device...
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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