Introduction

This repository contains STMicroelectronics MEMS IIO drivers for the following LTS Linux/Android kernels:

• 4.9 (EOL)
• 4.14
• 4.19
• 5.4
• 5.10
• 5.15
• 6.1
• 6.6
• 6.12

For EOL kernel the maintenance has been discontinued and is strongly discouraged from using it for new developments.

Source code integration

From your kernel source code directory add the git remote (i.e. stmems_iio_github) for this repository:

git remote add stmems_iio_github \
               https://github.com/STMicroelectronics/st-mems-android-linux-drivers-iio.git

Fetch the just added remote:

git fetch stmems_iio_github

There are now two ways to integrate the drivers code into the kernel target branch:

• merge (suggested strategy)
• rebase

merge

Merge the stmems_iio_github/master with your target kernel source branch (i.e branch linux-5.4.y):

git merge --allow-unrelated-histories \
          linux-5.4.y \
          stmems_iio_github/master

rebase

Rebase the stmems_iio_github/master on top of your target kernel source branch (i.e branch linux-5.4.y):

git rebase --no-fork-point \
           linux-5.4.y \
           stmems_iio_github/master

Note: older git versions (i.e.: 2.7.4) would require to use sligthly different options:

git merge --no-fork-point \
          linux-5.4.y \
          stmems_iio_github/master

git rebase -Xno-renames \
           --no-fork-point \
           linux-5.4.y \
           stmems_iio_github/master

Apply patches

Now that drivers code has been added to the target kernel branch, few patches needs to be added in order to:

• add STM drivers into Kconfig & Makefile systems
• patch IIO framework with custom events with custom events, channels and devices

Apply the patches available in the just added repository (i.e branch linux-5.4.y):

git am stm_iio_patches/5.4.y/*-stm-*.patch

Configuration

A folder named stm_iio_configs should now be available with the default configs for the supported drivers.

Modify target defconfig

Sensors defconfig can be appended to the board defconfig (i.e. if your current configuration file is arch/arm/configs/stm32_defconfig):

cat stm_iio_configs/lsm6dsm_defconfig >> arch/arm/configs/stm32_defconfig

Alternatively, it can be done at build time without altering the board config file, as follow.

Merge configuration

Driver config can be merged into current target pre-configured kernel using a script available in the kernel itself:

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnu-
scripts/kconfig/merge_config.sh -n .config stm_iio_configs/lsm6dsm_defconfig

Build Modules

This repo include Makefile for building in tree and out of tree modules

In Kernel Tree build

Set CROSS_COMPILE and ARCH accordingly to your target board. Follow an example for a RPI 4 target board (32 bits):

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnu-
make KCFLAGS=-Werror -j $(nproc)

Out of Kernel Tree build

The drivers in this project can also be build as external module. Follow an example for RPI 4 target board (32 bits):

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnu-
export KDIR=<the directory where Linux kernel is build>

# Specifying INSTALL_MOD_PATH the modules installation path will be:
# /INSTALL_MOD_PATH/lib/modules/$(KERNELRELEASE)/kernel/
# instead of /lib/modules/$(KERNELRELEASE)/extra/
export INSTALL_MOD_PATH=<modules installation path>

# Specifying INSTALL_MOD_DIR to set analternative name to "extra" path:
# /lib/modules/$(KERNELRELEASE)/INSTALL_MOD_DIR/ instead of standard
# /lib/modules/$(KERNELRELEASE)/extra/
export INSTALL_MOD_DIR=<modules alternate dir>

# Add flags "-Werror" for stop build on warning, then build the driver modules project:
make KCFLAGS=-Werror -C drivers/iio/stm/ $1 -j$(nproc)

# Install modules
make -C drivers/iio/stm/ modules_install

License

This software is distributed under the GNU General Public License v2.0