Bosch SMI240 Sensor HAL

1. Introduction

The SMI240 Sensor HAL (Hardware Abstraction Layer) implementation shall be used with the SMI240 kernel driver based on the Linux IIO subsystem.

2. Prerequisites

  • Familiarity with Linux kernel compilation and configuration

  • Basic knowledge of Android development and AOSP

  • The Android source tree is downloaded

3. Integration Steps

3.1 Linux Kernel with SMI240 IIO driver

  1. The SMI240 IIO driver documentation decribes how to build the Linux kernel.

  2. Integrate the kernel and build the AOSP project to ensure the Linux kernel is included in the build.

3.2 SMI240 Sensor HAL Integration

  1. Adapt your manifest file or manually clone the SMI240 Sensor HAL repository into the desired AOSP project’s directory, e.g. hardware/bosch/sensors/.

  2. Add the desired sensor HAL service, e.g. by modifying the device makefile (e.g., device/manufacturer/device_name/device.mk):

# For sensor hal 2.0
PRODUCT_PACKAGES += android.hardware.sensors@2.0-service.bosch
# For sensor hal 2.1
PRODUCT_PACKAGES += android.hardware.sensors@2.1-service.bosch
# For sensor hal AIDL
PRODUCT_PACKAGES += android.hardware.sensors@aidl-service.bosch
# For sensor multi hal 2.X
PRODUCT_PACKAGES += android.hardware.sensors@2.X-service.multihal bosch.sensor.multihal
PRODUCT_COPY_FILES += hardware/bosch/sensors/multihal/hals.conf:$(TARGET_COPY_OUT_VENDOR)/etc/sensors/hals.conf
# For sensor multi hal AIDL
PRODUCT_PACKAGES += android.hardware.sensors-service.multihal bosch.sensor.multihal
PRODUCT_COPY_FILES += hardware/bosch/sensors/multihal/hals.conf:$(TARGET_COPY_OUT_VENDOR)/etc/sensors/hals.conf

  1. Modify the sepolicy file_contexts file (e.g., device/manufacturer/device_name/sepolicy/file_contexts) by adding the following lines, depending on the HAL version used:

# For sensor hal 2.0
/vendor/bin/hw/android\.hardware\.sensors@2\.0-service\.bosch u:object_r:hal_sensors_default_exec:s0
# For sensor hal 2.1
/vendor/bin/hw/android\.hardware\.sensors@2\.1-service\.bosch u:object_r:hal_sensors_default_exec:s0
# For sensor hal AIDL
/vendor/bin/hw/android\.hardware\.sensors@aidl-service\.bosch u:object_r:hal_sensors_default_exec:s0
# For sensor multi hal 2.X
/vendor/bin/hw/android\.hardware\.sensors@2\.X-service\.multihal u:object_r:hal_sensors_default_exec:s0
# For sensor multi hal AIDL
/vendor/bin/hw/android\.hardware\.sensors-service\.multihal u:object_r:hal_sensors_default_exec:s0

  1. Build the AOSP project to ensure the SMI240 Sensor HAL compiles successfully.

4. Testing and Verification

  • Flash the built AOSP image onto your target device.

  • Verify that the SMI240 IIO driver was installed properly by checking the /sys/bus/iio/devices/iio:device0 directory.

  • Verify that the SMI240 Sensor HAL is functioning correctly by executing adb shell dumpsys sensorservice.