Re: [PATCH v2 1/2] dt-bindings: hwmon: moortec,mr75203: adapt multipleOf for T-Head TH1520

[Conor Dooley <conor@kernel.org>]

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On Fri, Mar 06, 2026 at 02:39:40AM +0800, Icenowy Zheng wrote:
> 在 2026-03-05四的 10:36 -0800，Drew Fustini写道：
> > On Thu, Mar 05, 2026 at 10:40:43PM +0800, Icenowy Zheng wrote:
> > > The G and J coefficients provided by T-Head TH1520 manual (which
> > > calls
> > > them A and C coefficients and calls H coefficient in the binding as
> > > B)
> > > has the 1/100 degree Celsius bit (the values are 42.74 and -0.16
> > > correspondingly), however the binding currently only allows
> > > cofficients
> > > as precise as 100 milli-Celsius (1/10 degree Celsius).
> > > 
> > > Change the multipleOf value of these two cofficients to 10 (in the
> > > unit
> > > of milli-Celsius) to satisfy the need of TH1520.
> > > 
> > > Signed-off-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>
> > > ---
> > > New patch in v2.
> > > 
> > >  Documentation/devicetree/bindings/hwmon/moortec,mr75203.yaml | 4
> > > ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git
> > > a/Documentation/devicetree/bindings/hwmon/moortec,mr75203.yaml
> > > b/Documentation/devicetree/bindings/hwmon/moortec,mr75203.yaml
> > > index 56db2292f062d..7d57c2934a8a1 100644
> > > --- a/Documentation/devicetree/bindings/hwmon/moortec,mr75203.yaml
> > > +++ b/Documentation/devicetree/bindings/hwmon/moortec,mr75203.yaml
> > > @@ -105,7 +105,7 @@ properties:
> > >        G coefficient for temperature equation.
> > >        Default for series 5 = 60000
> > >        Default for series 6 = 57400
> > > -    multipleOf: 100
> > > +    multipleOf: 10
> > >      minimum: 1000
> > >      $ref: /schemas/types.yaml#/definitions/uint32
> > >  
> > > @@ -131,7 +131,7 @@ properties:
> > >        J coefficient for temperature equation.
> > >        Default for series 5 = -100
> > >        Default for series 6 = 0
> > > -    multipleOf: 100
> > > +    multipleOf: 10
> > >      maximum: 0
> > >      $ref: /schemas/types.yaml#/definitions/int32
> > >  
> > > -- 
> > > 2.52.0
> > > 
> > 
> > I am wondering if there is any backwards compatibility issue but
> > there
> > are no other users of this compatible in mainline other than th1520.
> > There is also the precendent 030d2a0ce5dc ("dt-bindings: hwmon:
> > moortec,mr75203: fix multipleOf for coefficients") having change the
> > property. I suppose it is a not a problem unless other people on the
> > list raise an objection.
> 
> Well mathematically any number that is a multiple of 100 is a multiple
> of 10?
> 
> So theoretically there should be no compatibility issue.

Ye I don't think this is likely worth worrying about. The restrictions
exist in these kinds of cases to tell users they're doing the wrong
thing and using a value the hardware doesn't support, the driver almost
certainly will never care and just "blindly" use the number without
doing any validation, so as long as the multipleOf matches the
capability of the hardware you're okay.

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