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Subject: Re: Should regulator core support parsing OF based fwnode?
To:     Mark Brown <broonie@kernel.org>
CC:     <mark.rutland@arm.com>, <daniel.thompson@linaro.org>,
        Liam Girdwood <lgirdwood@gmail.com>, <tomi.valkeinen@ti.com>,
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        <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        <robh+dt@kernel.org>,
        Jacek Anaszewski <jacek.anaszewski@gmail.com>, <pavel@ucw.cz>,
        <lee.jones@linaro.org>, <linux-leds@vger.kernel.org>,
        <dmurphy@ti.com>
References: <20191003082812.28491-3-jjhiblot@ti.com>
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 <20191003183554.GA37096@sirena.co.uk>
 <25b9614f-d6be-9da5-0fe5-eb58c8c93850@gmail.com>
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 <a9f668f9-ad26-4e18-178a-8403b8b3b1db@gmail.com>
 <20191004113942.GB4866@sirena.co.uk>
 <b6318ba5-e76e-dc1c-6921-a702abf6749c@ti.com>
 <20191004144029.GC4866@sirena.co.uk>
From:   Jean-Jacques Hiblot <jjhiblot@ti.com>
Message-ID: <6df68ecb-f92e-fd9c-7f55-f66fa463263a@ti.com>
Date:   Fri, 4 Oct 2019 17:13:13 +0200
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On 04/10/2019 16:40, Mark Brown wrote:
> On Fri, Oct 04, 2019 at 03:33:13PM +0200, Jean-Jacques Hiblot wrote:
>> On 04/10/2019 13:39, Mark Brown wrote:
>>> Consumers should just be able to request a regulator without having to
>>> worry about how that's being provided - they should have no knowledge at
>>> all of firmware bindings or platform data for defining this.  If they
>>> do that suggests there's an abstraction issue somewhere, what makes you
>>> think that doing something with of_node is required?
>> The regulator core accesses consumer->of_node to get a phandle to a
>> regulator's node. The trouble arises from the fact that the LED core does
>> not populate of_node anymore, instead it populates fwnode. This allows the
>> LED core to be agnostic of ACPI or OF to get the properties of a LED.
> Why is the LED core populating anything?  Is the LED core copying bits
> out of the struct device for the actual device into a synthetic device
> rather than passing the actual device in?  That really doesn't seem like
> a good idea, it's likely to lead to things like this where you don't
> copy something that's required (or worse where something directly in the
> struct device that can't be copied is needed).

This is not a copy of a device of parent's of_node or something like that.

You can think of a LED controller as a bus. It 'enumerates' its children 
LED, create the children devices (one per LED) and provides the 
functions to interact with them.

The device node we are talking about here is a per-LED thing, it is a 
child node of the node of the LED controller.

here is an example:

     tlc59108: tlc59116@40 { /* this is the node for the LED controller */
         status = "okay";
         #address-cells = <1>;
         #size-cells = <0>;
         compatible = "ti,tlc59108";
         reg = <0x40>;

         backlight_led: led@2 { /* this is the node of one LED attached 
to pin#2 of the LED controller */
             power-supply = <&bkl_fixed>;
             reg = <0x2>;
         };
         other_led: led@3 { /* this is the node another LED attached to 
pin #3 of the LED controller */
             power-supply = <&reg_3v3>;
             reg = <0x3>;
         };
     };


>
>> IMO it is better to populate both of_node and fwnode in the LED core at the
>> moment. It has already been fixed this way for the platform driver [0], MTD
>> [1] and PCI-OF [2].
> Yeah, if you're going to be copying stuff out of the real device I'd
> copy the of_node as well.
>
>>> Further, unless you have LEDs that work without power you probably
>>> shouldn't be using _get_optional() for their supply.  That interface is
>>> intended only for supplies that may be physically absent.
>> Not all LEDs have a regulator to provide the power. The power can be
>> supplied by the LED controller for example.
> This code probably shouldn't be being run at all for LEDs like that, I
> was assuming this was just for GPIO LEDs and similar rather than all
> LEDs.

>
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