On Sun, Sep 4, 2022 at 11:51 PM Jakob Hauser <jahau@xxxxxxxxxxxxxx> wrote: > 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@xxxxxxxxxxx> > Signed-off-by: Jakob Hauser <jahau@xxxxxxxxxxxxxx> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx> Yours, Linus Walleij
