[PATCH] dt-bindings: thermal: Use signed integers for coefficients

[PATCH] dt-bindings: thermal: Use signed integers for coefficients

[Daniel Lezcano]

The coefficients property describes the coefficients of a linear
equation used to derive a thermal zone temperature. Both the slope
and the constant offset can be negative, and the thermal core stores
them as signed integers.

Existing Device Trees already rely on signed values. OMAP4460 uses
an offset of -9301, while OMAP5 uses offsets of -1791 and -2992.
Broadcom platforms also use negative slopes. Declaring the property
as uint32-array does not represent these values correctly.

Change the property type to int32-array so schema validation decodes
the cells as signed 32-bit integers, matching their intended meaning
and the thermal implementation. The cell width and binary encoding
remain unchanged, preserving compatibility with existing Device
Trees.

Fixes: 1202a442a31f ("dt-bindings: thermal: Add yaml bindings for thermal zones")
Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
---
 Documentation/devicetree/bindings/thermal/thermal-zones.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
index 999ad40a20d5..72e419124f98 100644
--- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
+++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
@@ -101,7 +101,7 @@ patternProperties:
           thermal zone.
 
       coefficients:
-        $ref: /schemas/types.yaml#/definitions/uint32-array
+        $ref: /schemas/types.yaml#/definitions/int32-array
         description:
           An array of integers containing the coefficients of a linear equation
           that binds all the sensors listed in this thermal zone.
-- 
2.43.0

Re: [PATCH] dt-bindings: thermal: Use signed integers for coefficients

[Lukasz Luba]

Hi Daniel,

On 11/3/26 21:43, Daniel Lezcano wrote:
> The coefficients property describes the coefficients of a linear
> equation used to derive a thermal zone temperature. Both the slope
> and the constant offset can be negative, and the thermal core stores
> them as signed integers.
> 
> Existing Device Trees already rely on signed values. OMAP4460 uses
> an offset of -9301, while OMAP5 uses offsets of -1791 and -2992.
> Broadcom platforms also use negative slopes. Declaring the property
> as uint32-array does not represent these values correctly.

This looks like a good argument which was missed back then (that
the negative values are possible).

> 
> Change the property type to int32-array so schema validation decodes
> the cells as signed 32-bit integers, matching their intended meaning
> and the thermal implementation. The cell width and binary encoding
> remain unchanged, preserving compatibility with existing Device
> Trees.
> 
> Fixes: 1202a442a31f ("dt-bindings: thermal: Add yaml bindings for thermal zones")
> Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
> ---
>   Documentation/devicetree/bindings/thermal/thermal-zones.yaml | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
> index 999ad40a20d5..72e419124f98 100644
> --- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
> +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
> @@ -101,7 +101,7 @@ patternProperties:
>             thermal zone.
>   
>         coefficients:
> -        $ref: /schemas/types.yaml#/definitions/uint32-array
> +        $ref: /schemas/types.yaml#/definitions/int32-array
>           description:
>             An array of integers containing the coefficients of a linear equation
>             that binds all the sensors listed in this thermal zone.

Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

Regards,
Lukasz

Re: [PATCH] dt-bindings: thermal: Use signed integers for coefficients

[Daniel Lezcano]

Hi Lukasz,

On 11/5/26 11:45, Lukasz Luba wrote:
> Hi Daniel,
> 
> On 11/3/26 21:43, Daniel Lezcano wrote:
>> The coefficients property describes the coefficients of a linear
>> equation used to derive a thermal zone temperature. Both the slope
>> and the constant offset can be negative, and the thermal core stores
>> them as signed integers.
>>
>> Existing Device Trees already rely on signed values. OMAP4460 uses
>> an offset of -9301, while OMAP5 uses offsets of -1791 and -2992.
>> Broadcom platforms also use negative slopes. Declaring the property
>> as uint32-array does not represent these values correctly.
> 
> This looks like a good argument which was missed back then (that
> the negative values are possible).
> 
>>
>> Change the property type to int32-array so schema validation decodes
>> the cells as signed 32-bit integers, matching their intended meaning
>> and the thermal implementation. The cell width and binary encoding
>> remain unchanged, preserving compatibility with existing Device
>> Trees.
>>
>> Fixes: 1202a442a31f ("dt-bindings: thermal: Add yaml bindings for 
>> thermal zones")
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
>> ---
>>   Documentation/devicetree/bindings/thermal/thermal-zones.yaml | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/thermal/thermal- 
>> zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
>> index 999ad40a20d5..72e419124f98 100644
>> --- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
>> +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
>> @@ -101,7 +101,7 @@ patternProperties:
>>             thermal zone.
>>         coefficients:
>> -        $ref: /schemas/types.yaml#/definitions/uint32-array
>> +        $ref: /schemas/types.yaml#/definitions/int32-array
>>           description:
>>             An array of integers containing the coefficients of a 
>> linear equation
>>             that binds all the sensors listed in this thermal zone.
> 
> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Thanks for the review

Re: [PATCH] dt-bindings: thermal: Use signed integers for coefficients

[Krzysztof Kozlowski]

On Tue, Nov 03, 2026 at 10:43:57PM +0100, Daniel Lezcano wrote:
> The coefficients property describes the coefficients of a linear
> equation used to derive a thermal zone temperature. Both the slope
> and the constant offset can be negative, and the thermal core stores
> them as signed integers.
> 
> Existing Device Trees already rely on signed values. OMAP4460 uses
> an offset of -9301, while OMAP5 uses offsets of -1791 and -2992.
> Broadcom platforms also use negative slopes. Declaring the property
> as uint32-array does not represent these values correctly.
> 
> Change the property type to int32-array so schema validation decodes
> the cells as signed 32-bit integers, matching their intended meaning
> and the thermal implementation. The cell width and binary encoding
> remain unchanged, preserving compatibility with existing Device
> Trees.
> 
> Fixes: 1202a442a31f ("dt-bindings: thermal: Add yaml bindings for thermal zones")
> Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
> ---
>  Documentation/devicetree/bindings/thermal/thermal-zones.yaml | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

drivers/thermal/thermal_of.c still uses u32. Maybe we should have
of_property_read_s32_array() wrapper so the binding can match the ABI
code exactly?

Rob?

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof

Re: [PATCH] dt-bindings: thermal: Use signed integers for coefficients

[Rob Herring]

On Fri, Nov 06, 2026 at 02:03:24PM +0100, Krzysztof Kozlowski wrote:
> On Tue, Nov 03, 2026 at 10:43:57PM +0100, Daniel Lezcano wrote:
> > The coefficients property describes the coefficients of a linear
> > equation used to derive a thermal zone temperature. Both the slope
> > and the constant offset can be negative, and the thermal core stores
> > them as signed integers.
> > 
> > Existing Device Trees already rely on signed values. OMAP4460 uses
> > an offset of -9301, while OMAP5 uses offsets of -1791 and -2992.
> > Broadcom platforms also use negative slopes. Declaring the property
> > as uint32-array does not represent these values correctly.
> > 
> > Change the property type to int32-array so schema validation decodes
> > the cells as signed 32-bit integers, matching their intended meaning
> > and the thermal implementation. The cell width and binary encoding
> > remain unchanged, preserving compatibility with existing Device
> > Trees.
> > 
> > Fixes: 1202a442a31f ("dt-bindings: thermal: Add yaml bindings for thermal zones")
> > Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
> > ---
> >  Documentation/devicetree/bindings/thermal/thermal-zones.yaml | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> drivers/thermal/thermal_of.c still uses u32. Maybe we should have
> of_property_read_s32_array() wrapper so the binding can match the ABI
> code exactly?
> 
> Rob?

Yes, please. I did a pass fixing type mismatches so it would be good to 
not add new ones.

Rob