[PATCH] dt-bindings: iio: adc: lltc,ltc2497: Make vref-supply optional for LTC2305/LTC2309

[PATCH] dt-bindings: iio: adc: lltc,ltc2497: Make vref-supply optional for LTC2305/LTC2309

[Kyle Hsieh]

The LTC2305 and LTC2309 have an internal 4.096V reference, so their REF
pin does not need to be driven by an external supply. The LTC2497 and
LTC2499 have no internal reference and require one.

Only require vref-supply for the LTC2497 and LTC2499, so boards using
the internal reference can be described without a dummy regulator.

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
The ltc2309 driver already uses the internal reference when vref-supply
is absent. This is needed by the Meta Ventura2 BMC devicetree, which
describes LTC2305 ADCs that use their internal reference:
https://lore.kernel.org/all/20261106-ventura2-dts-update-v1-0-b085ece9bf57@gmail.com/
---
 .../devicetree/bindings/iio/adc/lltc,ltc2497.yaml      | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
index 4df5aadd1e1d..22abc6885b5a 100644
--- a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
@@ -47,14 +47,28 @@ properties:
       - lltc,ltc2499
 
   reg: true
-  vref-supply: true
+  vref-supply:
+    description:
+      Reference voltage supply. The LTC2305 and LTC2309 have an internal
+      4.096V reference which is used when this property is absent.
   "#io-channel-cells":
     const: 1
 
 required:
   - compatible
   - reg
-  - vref-supply
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - lltc,ltc2497
+              - lltc,ltc2499
+    then:
+      required:
+        - vref-supply
 
 additionalProperties: false
 

---
base-commit: 1390ca4953a7400ca932cb49635f02c727f885a6
change-id: 20261110-ltc2497-vref-optional-4bf34d6b3304

Best regards,
-- 
Kyle Hsieh <kylehsieh1995@gmail.com>

Re: [PATCH] dt-bindings: iio: adc: lltc,ltc2497: Make vref-supply optional for LTC2305/LTC2309

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] dt-bindings: iio: adc: lltc,ltc2497: vref-supply not required
  for lltc,ltc2493
--

commit 9ef21ec87b9693cbb7eb2ce20677fc640b5dbba6
Author: Kyle Hsieh <kylehsieh1995@gmail.com>

dt-bindings: iio: adc: lltc,ltc2497: Make vref-supply optional for LTC2305/LTC2309

This commit removes vref-supply from the top-level required list in
lltc,ltc2497.yaml and adds a conditional requirement for lltc,ltc2497 and
lltc,ltc2499 so that LTC2305 and LTC2309 nodes can omit it when using
their internal reference.

> diff --git a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
> index 4df5aadd1e1d7..22abc6885b5a2 100644
> --- a/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml
> @@ -47,14 +47,28 @@ properties:
>        - lltc,ltc2499
>  
>    reg: true
> -  vref-supply: true
> +  vref-supply:
> +    description:
> +      Reference voltage supply. The LTC2305 and LTC2309 have an internal
> +      4.096V reference which is used when this property is absent.
>    "#io-channel-cells":
>      const: 1
>  
>  required:
>    - compatible
>    - reg
> -  - vref-supply
> +
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - lltc,ltc2497
> +              - lltc,ltc2499
> +    then:
> +      required:
> +        - vref-supply

[Severity: Medium]
Should lltc,ltc2493 also be included in this enum?

This binding also covers lltc,ltc2493, which like the LTC2497 and LTC2499
has no internal voltage reference and relies on the external vref
regulator in ltc2497core_probe() and ltc2497core_read_raw().  Removing
vref-supply from the top-level required list without adding lltc,ltc2493
to the conditional makes vref-supply optional for LTC2493 nodes.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110-ltc2497-vref-optional-v1-1-35c9657f3c0f@gmail.com?part=1