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Date:   Sun, 23 Jul 2023 10:29:25 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Martin Kepplinger <martink@posteo.de>
Cc:     lorenzo@kernel.org, lars@metafoo.de, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        kernel@puri.sm, linux-iio@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dt-bindings: iio: imu: st,lsm6dsx: add mount-matrix
 property
Message-ID: <20230723102925.3d5f1c40@jic23-huawei>
In-Reply-To: <20230721103410.575555-1-martink@posteo.de>
References: <20230721103410.575555-1-martink@posteo.de>
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On Fri, 21 Jul 2023 10:34:10 +0000
Martin Kepplinger <martink@posteo.de> wrote:

> Add the mount-matrix optional property to the binding since it's supported
> and very useful when using the chip on a board.
> 
> Signed-off-by: Martin Kepplinger <martink@posteo.de>

Hi Martin,

A question on the example.

> ---
>  Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml b/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml
> index b39f5217d8ff..443dce326c5e 100644
> --- a/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml
> +++ b/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml
> @@ -93,6 +93,9 @@ properties:
>    wakeup-source:
>      $ref: /schemas/types.yaml#/definitions/flag
>  
> +  mount-matrix:
> +    description: an optional 3x3 mounting rotation matrix
> +
>  required:
>    - compatible
>    - reg
> @@ -114,6 +117,9 @@ examples:
>              reg = <0x6b>;
>              interrupt-parent = <&gpio0>;
>              interrupts = <0 IRQ_TYPE_EDGE_RISING>;
> +            mount-matrix =  "1",  "0",  "0",
> +                            "0",  "1",  "0",
> +                            "0",  "0", "-1";

That's not a rotation matrix - so it's not a valid example...
IIRC it's a rotoinversion (determinant -1 whereas should be 1 for
a rotation matrix)
If a device is doing this we have a disagreement wrt to whether
it is using a left or right handed axis - which is a problem, though
one that is tricky to fix without causing people all sorts of problems..

Jonathan


>          };
>      };
>  ...