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Add magnetometer Yamaha YAS537 to the DeviceTree of samsung-serranove. The YAS537 variant was recently added to the Yamaha YAS magnetometers driver [1]. In the DeviceTree of samsung-serranove for the Android kernel, there is unfortunately no information on interrupts or pinctrl [2]. In the Android kernel driver for magnetometer Yamaha YAS537, there is a device-specific matrix to correct an ellipsoid shape of the measure values into a sphere shape [3]. This could be converted and applied to a mount-matrix. However, the current state of the mainline Yamaha YAS537 driver needs post-process calibration in userspace anyway, as it lacks a formula to center the measure values around zero. The correction of the ellipsoid into a sphere can be done in the post-process calibration as well. A mount-matrix is needed nonetheless. When putting samsung-serranove flat on a table in portrait orientation heading north, the Yamaha YAS537 magnetometer axes natively point X+ to north, Y+ to east and Z+ into the ground, which corresponds to a common way to define the Earth's magnetic field coordinate system [4]. According to the IIO definition, it should be Y+ to north, X+ to east and Z+ upwards [5], which corresponds to a common device coordinate system and eases sensor fusing. [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/iio/magnetometer/yamaha-yas530.c?id=65f79b501030678393eae0ae03d60a8151fbef55 [2] https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/GT-I9195I/arch/arm/boot/dts/samsung/msm8916/msm8916-sec-serranovelte-eur-r03.dtsi#L318-L321 [3] https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/GT-I9195I/drivers/iio/magnetometer/yas_mag_drv-yas537.c#L105-L106 [4] https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Characteristics [5] https://github.com/torvalds/linux/blob/v5.19/Documentation/devicetree/bindings/iio/mount-matrix.txt#L93-L126 Cc: Stephan Gerhold <stephan@gerhold.net> Signed-off-by: Jakob Hauser <jahau@rocketmail.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Bjorn Andersson <andersson@kernel.org> Link: https://lore.kernel.org/r/20220904214935.31032-1-jahau@rocketmail.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.