Re: [PATCH V4 3/8] backlight: qcom-wled: Add new properties for PMI8998

[kgunda]

On 2018-09-04 00:25, Bjorn Andersson wrote:
> On Wed 15 Aug 22:23 PDT 2018, kgunda@xxxxxxxxxxxxxx wrote:
>
> > On 2018-08-07 10:53, Bjorn Andersson wrote:
> > > On Mon 09 Jul 03:22 PDT 2018, Kiran Gunda wrote:
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/leds/backlight/qcom-wled.txt
> > > > b/Documentation/devicetree/bindings/leds/backlight/qcom-wled.txt
> > > [..]
> > > >  - qcom,num-strings
> > > >  	Usage:        optional
> > > >  	Value type:   <u32>
> > > >  	Definition:   #; number of led strings attached;
> > > > -		      value from 1 to 3. default: 2
> > > > -		      This property is supported only for PM8941.
> > > > +		      value: For PM8941 from 1 to 3.
> > > > +			     For PMI8998 from 1 to 4.
> > > [..]
> > > > +- qcom,enabled-strings
> > > > +	Usage:        optional
> > > > +	Value tyoe:   <u32 array>
> > > > +	Definition:   Array of the WLED strings numbered from 0 to 3. Each
> > > > +		      string of leds are operated individually. Specify the
> > > > +		      list of strings used by the device. Any combination of
> > > > +		      led strings can be used.
> > > [..]
> > > >
> > > >  Example:
> > > >
> > > > @@ -99,4 +146,5 @@ pm8941-wled@d800 {
> > > >  	qcom,switching-freq = <1600>;
> > > >  	qcom,ovp = <29>;
> > > >  	qcom,num-strings = <2>;
> > > > +	qcom,enabled-strings = <0x00 0x01>;
> > >
> > > Nit. I would assume that specifying qcom,num-strings = <2> implies that
> > > the first 2 strings are used, so one would not also specify
> > > qcom,enabled-strings.
> > >
> > Thanks Bjorn for reviewing the series !
> >
> > "qcom,enabled-strings" need be specified along with the 
> > "qcom,num-strings".
> > Because the enabled-strings can be <0, 2> or <0, 3 > also. The driver 
> > picks
> > the string
> > configuration from the enabled-strings array and enable only those
> > current-sinks.
>
> The original binding described qcom,num-strings to mean "the first N
> strings", requiring qcom,enabled-strings now would break backwards
> compatibility with this binding.
>
> In the case that qcom,enabled-strings is specified we can easily derive
> num-strings from the listed entires. So I would suggest that you look
> for enabled-strings and if not found fall back to checking for
> num-strings.
>
> Regards,
> Bjorn

Sorry for the late reply. Actually the "qcom,enabled-strings" is 
initialized with
the strings 0, 1, 2, 3 in the driver. Even though this property is 
missing the first
N strings will be still configured with out any issue, based on the 
"qcom,num-strings".