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From: "Vaittinen, Matti" <Matti.Vaittinen@fi.rohmeurope.com>
To: "mazziesaccount@gmail.com" <mazziesaccount@gmail.com>,
	"info@metux.net" <info@metux.net>
Cc: "dmurphy@ti.com" <dmurphy@ti.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"mark.rutland@arm.com" <mark.rutland@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"pavel@ucw.cz" <pavel@ucw.cz>,
	"linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
	"jacek.anaszewski@gmail.com" <jacek.anaszewski@gmail.com>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>
Subject: Re: [RFC PATCH 0/5] leds: Add DT node finding and parsing to core
Date: Wed, 20 Nov 2019 07:37:42 +0000
Message-ID: <e29bb49931542c55c867f52c82f11421454c0f64.camel@fi.rohmeurope.com> (raw)
In-Reply-To: <56d3a81e-f675-fd5e-06a7-8039bf02468e@metux.net>


On Tue, 2019-11-19 at 20:52 +0100, Enrico Weigelt, metux IT consult
wrote:
> On 18.11.19 11:38, Vaittinen, Matti wrote:
> 
> Hi,
> 
> > > a) existing DT's (in the field) become incompatible with newer
> > >    kernel versions
> > 
> > This was my main concern. This of course would not mean that we
> > could
> > not take this approach for new LED controller drivers - but that
> > would
> > (probably) lead to dual led registration interface 
> 
> Maybe just a flag for that ? Perhaps the driver could also specify a
> list of node names for the LEDs, so led-core can do the lookup for
> them.

This is actually close to what I suggested in my other email to Jacek.

> > > b) existing userlands that rely on speicific LED names become
> > >    incomatible with newer kernel versions.
> > 
> > I didn't even think this far, but yes, I see... LED node name might
> > be
> > reflected in user-space LED name. I won't start arguing if this is
> > sane
> > or not - this is what we seem to be living with today :)
> 
> Especially in embedded world, this can really make sense:
> applications
> just use a defined LED name, no matter which board it's running on.
> Convention over configuration.

Definitely. I am all for generating the name based on LED _function_ -
no matter what the board is. I like the LED name generation base on
'function' DT property. But node names tend to be somewhat generic - or
board specific (to avoid collisions). So using node name directly is
not (as far as my understanding goes - which is limited on this topic)
optimal for guaranteeing coherent view (across the boards) for user-
space. Wow, what a nice sentence for non native English speaker like me
xD

> Personally, I also like to use LED subsystem as frontend for things
> like
> gpio-driven relais, etc, and assign semantically fitting names
> instead
> of "technical" ones,

This is outside of my experience so I just believe what you say :)

> 
> > I didn't invest too much of time on this yet - but at first glimpse
> > it
> > seemed that at least some of the drivers did use reg - property
> > with
> > fixed value to do the matching. Those could set the property name
> > to
> > 'reg' and value to 'X' and leave the DT node lookup and common
> > property
> > parsing to the LED core. If my patch won't get too big objection
> > (and
> > if no fatal flaws are found from the idea) - then I might try and
> > find
> > the time to do some follow-up patches simplifying existing LED
> > drivers...
> 
> Sounds good :)
> 
> 
> --mtx
> 


      reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-29 12:46 Matti Vaittinen
2019-10-29 12:46 ` [RFC PATCH 1/5] leds: Add common LED binding parsing support to LED class/core Matti Vaittinen
2019-10-29 12:47 ` [RFC PATCH 2/5] dt-bindings: an30259a: example for using fixed LED node names Matti Vaittinen
2019-11-06  3:42   ` Rob Herring
2019-11-06 11:30     ` SPAM (R/EU IT) // " Vaittinen, Matti
2019-10-29 12:47 ` [RFC PATCH 3/5] leds: an30259a: Offload DT node locating and parsing to core Matti Vaittinen
2019-10-29 12:48 ` [RFC PATCH 4/5] dt-bindings: lm3692x: example for using fixed LED node names Matti Vaittinen
2019-10-29 12:48 ` [RFC PATCH 5/5] leds: lm3692x: Offload DT node locating and parsing to core Matti Vaittinen
2019-11-18  9:21 ` [RFC PATCH 0/5] leds: Add DT node finding " Enrico Weigelt, metux IT consult
2019-11-18 10:38   ` Vaittinen, Matti
2019-11-19 19:52     ` Enrico Weigelt, metux IT consult
2019-11-20  7:37       ` Vaittinen, Matti [this message]

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