Re: Should regulator core support parsing OF based fwnode?

[Jean-Jacques Hiblot]

On 04/10/2019 17:58, Mark Brown wrote:
> On Fri, Oct 04, 2019 at 05:13:13PM +0200, Jean-Jacques Hiblot wrote:
> > On 04/10/2019 16:40, Mark Brown wrote:
> > > 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>;
> >          };
> Regulator supplies are supposed to be defined at the chip level rather
> than subfunctions with names corresponding to the names on the chip.
> This ensures that all chips look similar when you're mapping the
> schematic into a DT, you shouldn't need to know about the binding for a
> given chip to write a DT for it and if multiple people (perhaps working
> on different OSs) write bindings for the same chip there should be a
> good chance that they come up with the same mapping.  The supply_alias
> interface is there to allow mapping these through to subfunctions if
> needed, it looks like the LED framework should be using this.

In case of current-sink LED drivers, each LED can be powered by a 
different regulator, because the driver is only a switch between the LED 
cathod and the ground.

> That said if you are doing the above and the LEDs are appearing as
> devices it's extremely surprising that their of_node might not be
> initialized.

That is because this is usually done by the platform core which is not 
involved here.

JJ