linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: max30100: Add pulse-width property

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Message-ID: <20251004141231.632c311d@jic23-huawei>
Date: Sat, 4 Oct 2025 14:12:31 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Shrikant Raskar <raskar.shree97@...il.com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 dlechner@...libre.com, nuno.sa@...log.com, andy@...nel.org,
 matt@...ostay.sg, skhan@...uxfoundation.org, david.hunter.linux@...il.com,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH 1/2] dt-bindings: iio: max30100: Add pulse-width
 property

On Sat,  4 Oct 2025 07:26:22 +0530
Shrikant Raskar <raskar.shree97@...il.com> wrote:

> The MAX30100 sensor supports multiple LED pulse widths (200us, 400us,
> 800us, 1600us). These settings affect measurement resolution and power
> consumption. Until now, the driver always defaulted to 1600us.
> 
> Introduce a new device tree property `maxim,pulse-width` that allows
> users to select the desired pulse width in microseconds from device
> tree.
> 
> Valid values are: 200, 400, 800, 1600.
> 
> This prepares for driver changes that read this property and configure
> the SPO2 register accordingly.
> 
> Signed-off-by: Shrikant Raskar <raskar.shree97@...il.com>
Hi Shrikant,

Explain why this is in some way related to characteristics of how the
system containing this chip is built (wiring, lenses etc).  Otherwise
this might instead be something that should be controlled from userspace
not firmware.

Also, give a little more on why we care about controlling it at all.
Is there a usecase where power use of this chip matters?  Mostly I'd expect
it to be in measurement equipment with relatively short measuring periods.

Jonathan

> ---
>  .../devicetree/bindings/iio/health/maxim,max30100.yaml      | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/health/maxim,max30100.yaml b/Documentation/devicetree/bindings/iio/health/maxim,max30100.yaml
> index 967778fb0ce8..55aaf2ff919b 100644
> --- a/Documentation/devicetree/bindings/iio/health/maxim,max30100.yaml
> +++ b/Documentation/devicetree/bindings/iio/health/maxim,max30100.yaml
> @@ -27,6 +27,11 @@ properties:
>        LED current whilst the engine is running. First indexed value is
>        the configuration for the RED LED, and second value is for the IR LED.
>  
> +  maxim,pulse-width:
> +    maxItems: 1
> +    description: Pulse width in microseconds
> +    enum: [200, 400, 800, 1600]
> +
>  additionalProperties: false
>  
>  required:
> @@ -44,6 +49,7 @@ examples:
>              compatible = "maxim,max30100";
>              reg = <0x57>;
>              maxim,led-current-microamp = <24000 50000>;
> +            maxim,pulse-width = <1600>;
>              interrupt-parent = <&gpio1>;
>              interrupts = <16 2>;
>          };