Re: [PATCH 1/2] dt-bindings: backlight: Convert LP8860 into YAML format adding LP886x

["Sverdlin, Alexander" <alexander.sverdlin@siemens.com>]

Hi Andrew,

On Fri, 2024-12-06 at 12:02 -0600, Andrew Davis wrote:
> On 12/6/24 11:46 AM, Sverdlin, Alexander wrote:
> > Hi Andrew,
> > 
> > On Fri, 2024-12-06 at 11:43 -0600, Andrew Davis wrote:
> > > > Are you sure this is a correct thing to do? The lp8860-q1 product link
> > > > cites it as being a 4-channel device. Even if the kernel only ever
> > > > supports it as a single-channel device, the binding should reflect what
> > > > it is capable of doing.
> > > > 
> > > 
> > > Agree, the driver today just checks the first child node, but it could
> > > be extended for all 4 supported LED channels, and we shouldn't have
> > > to change the binding for that new support.
> > 
> > but the channels are (in my understanding) for power-balancing only, there
> > are no separate controls for them. What do I miss?
> > 
> 
> I'm not very familiar with this part either, but looking at the datasheet
> I see:
> 
> > Supports Display Mode (Global Dimming) and
> > Cluster Mode (Independent Dimming)
> 
> > In Cluster mode LED strings have independent control but fewer features enabled than in Display Mode.

thanks for looking into this!

> And one channel controlling the others is only in this "Display Mode",
> but the currents to the others can be independently controlled in a
> different mode (seems these modes have less features which is probably
> why the driver doesn't make use of that today).

You are right! This seems to be the feature of the legacy lp8860.
Shall I then leave its binding alone and re-submit new YAML binding as-is
for the newer LP8864/LP8866 family? Seems that they don't have the cluster mode
any more.

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com