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Date:   Thu, 17 Nov 2022 16:54:02 +0000
From:   Jonathan Cameron <Jonathan.Cameron@huawei.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
CC:     Gerald Loacker <gerald.loacker@wolfvision.net>,
        <linux-iio@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Nikita Yushchenko <nikita.yoush@cogentembedded.com>,
        Jakob Hauser <jahau@rocketmail.com>,
        Michael Riesch <michael.riesch@wolfvision.net>
Subject: Re: [PATCH 1/2] dt-bindings: iio: magnetometer: add ti tmag5273
 documentation file
Message-ID: <20221117165402.000043c0@huawei.com>
In-Reply-To: <8c2da24c-ae10-40c9-bb3e-b300975a86d7@linaro.org>
References: <20221115073718.2377311-1-gerald.loacker@wolfvision.net>
        <20221115073718.2377311-2-gerald.loacker@wolfvision.net>
        <20221115174355.00004a01@Huawei.com>
        <f52dcb6d-30ec-3d49-7e28-9761462d4799@wolfvision.net>
        <8c2da24c-ae10-40c9-bb3e-b300975a86d7@linaro.org>
Organization: Huawei Technologies R&D (UK) Ltd.
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On Thu, 17 Nov 2022 17:17:24 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:

> On 17/11/2022 17:12, Gerald Loacker wrote:
> >>  
> >>> +
> >>> +  compatible:
> >>> +    const: ti,tmag5273
> >>> +
> >>> +  reg:
> >>> +    maxItems: 1
> >>> +
> >>> +  "#io-channel-cells":
> >>> +    const: 1
> >>> +
> >>> +  ti,angle-enable:
> >>> +    description:
> >>> +      Enables angle measurement in the selected plane.
> >>> +      0 = OFF
> >>> +      1 = X-Y (default)
> >>> +      2 = Y-Z
> >>> +      3 = X-Z  
> >>
> >> This feels like something we should be configuring at runtime rather that
> >> DT, or is it driven by board design or similar?
> >>  
> > 
> > We use this sensor for a zoom wheel application, there is an EVM from TI
> > for this as well. So this is for setting the mounting position of the wheel.  
> 
> That's ok, but does not explain why choice of angle measurement should
> be a property of the hardware. I could imagine configuring device to
> measure sometimes X-Y and sometimes X-Z, depending on the use case. Use
> case can change runtime.

If it's part of a physical device mounting, may well not be changeable at runtime
(at least not with out a screw driver / hacksaw etc.  Not really different form
arguing someone might rewire a sensor at runtime.  In theory possible but if they
do they are on their own - mostly we don't bother supporting them doing that.

So I think this is probably valid as a DT property.


> 
> 
> Best regards,
> Krzysztof
>