Kernel driver inv-mpu-iio
Author: InvenSense, Inc.


Table of Contents
=================
- Description
- Integrating the Driver in the Linux Kernel
- Dts file
- Communicating with the Driver in Userspace


Description
===========
This document describes how to install the Invensense device driver into a
Linux kernel. The supported chips are listed in Kconfig and user selects an
appropriate one from .e.g. menuconfig.


Integrating the Driver in the Linux Kernel
==========================================
Please add the files as follows (kernel 3.10):
- Copy mpu.h to <kernel_root>/include/linux/iio/imu/
- Copy inv_mpu folder under <kernel_root>/drivers/iio/imu/

In order to see the driver in menuconfig when building the kernel, please
make modifications as shown below:

    add "source "drivers/iio/imu/inv_mpu/Kconfig""
      in <kernel_root>/drivers/iio/imu/Kconfig

    add "obj-y += inv_mpu/"
      in <kernel_root>/drivers/iio/imu/Makefile



Dts file
========
In order to recognize the Invensense device on the I2C/SPI bus, dts(or dtsi)
file must be modified.

Example)
ICM20648 + AK09911/BMP280/APDS9930 on AUX I2C

    i2c@f9968000 {
        /* Invensense */
        mpu6515_acc@68 {
            compatible = "inven,icm20648";
            reg = <0x68>;
            interrupt-parent = <&msmgpio>;
            interrupts = <73 0x2>;
            inven,vdd_ana-supply = <&pm8941_l17>;
            inven,vcc_i2c-supply = <&pm8941_lvs1>;
            inven,gpio_int1 = <&msmgpio 73 0x00>;
            fs_range = <0x00>;
            /* mount matrix */
            axis_map_x = <1>;
            axis_map_y = <0>;
            axis_map_z = <2>;
            negate_x = <0>;
            negate_y = <0>;
            negate_z = <1>;
            poll_interval = <200>;
            min_interval = <5>;
            inven,secondary_reg = <0x0c>;
            /* If no compass sensor,
             * replace "compass" with "none"
             */
            inven,secondary_type = "compass";
            inven,secondary_name = "ak09911";
            inven,secondary_axis_map_x = <1>;
            inven,secondary_axis_map_y = <0>;
            inven,secondary_axis_map_z = <2>;
            inven,secondary_negate_x = <1>;
            inven,secondary_negate_y = <1>;
            inven,secondary_negate_z = <1>;
            /* If no pressure sensor,
             * replace "pressure" with "none"
             */
            inven,aux_type = "pressure";
            inven,aux_name = "bmp280";
            inven,aux_reg = <0x76>;
            /* If no ALS sensor
             * replace "als" with "none"
             */
            inven,read_only_slave_type = "als";
            inven,read_only_slave_name = "apds9930";
            inven,read_only_slave_reg = <0x39>;
        };
    };


Communicating with the Driver in Userspace
==========================================
The driver generates several files in sysfs upon installation.
These files are used to communicate with the driver. The files can be found at:

(I2C) /sys/devices/*.i2c/i2c-*/*-*/iio:device*
(SPI) /sys/devices/*.spi/spi_master/spi*/spi*.*/iio:device*

Group and Owner for all entries should be updated to system/system at
boot time to allow userspace to access properly.


License
=======
Copyright (C) 2018 InvenSense, Inc.

This software is licensed under the terms of the GNU General Public
License version 2, as published by the Free Software Foundation, and
may be copied, distributed, and modified under those terms.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.