Should regulator core support parsing OF based fwnode?

Jean-Jacques Hiblot jjhiblot at
Fri Oct 4 15:13:13 UTC 2019

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 at 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 at 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 at 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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