How to customize the STM32MPU distribution for Android

This articles explain how you can customize the STM32MPU distribution for Android™. It's intent to be used by distribution package users.

1 Prerequisites[edit]

The environment used must have been installed using the right Distribution Package for your selected microprocessor device. See Distribution_Package.

To be able to execute following instructions you need to work from your distribution root directory and initialise your environment:

PC $> source build/envsetup.sh
PC $> lunch aosp-<BoardId>-userdebug

2 Layout configuration[edit]

It is possible to configuration the memory layout. The file android_layout.config located device/stm/<STM32Series>/layout contains all the necessary data.

When changes is done you need to reload the environment with:

PC $> source build/envsetup.sh
PC $> lunch aosp-<BoardId>-userdebug

2.1 Memory type[edit]

To adapt your build to the memory you desire, you must change in the file android_layout.config the parameter PART_MEMORY_TYPE.

For example the possible values can be:

  • sd
  • emmc

2.2 Memory size[edit]

To adapt your build to the size of your memory you can change in the file android_layout.config the parameter PART_MEMORY_SIZE.

For example the possible values can be:

  • 4GiB
  • 8GiB

This value must match the parameter at the end of the file that looks like PART_<Memory size>_MEMORY_MAX_SIZE

It may be necessary to change the value attach to this parameter. For example:

PART_8GiB_MEMORY_MAX_SIZE 7432M x1 sd

The 7536M must be adapt if your memory is less than its definition.

To find the correct value execute:

PC $> sgdisk -p /dev/mmcblk<x>

It will output something looking like:

Disk /dev/mmcblk0: 15433728 sectors, 7.4 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXX
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 15433694
Partitions will be aligned on 2-sector boundaries
Total free space is 0 sectors (0 bytes)

First line show the microSD card available size: here 15433728 sectors.

To calculate the size in MiB:

size = (NbSectors * SectorSize) / 1024 / 1024
In this example: (15433728 * 512) / 1024 / 1024 = 7536 MiB

Report this value for the parameter PART_8GiB_MEMORY_MAX_SIZE

PART_8GiB_MEMORY_MAX_SIZE 7536M x1 sd

You can refer to the README file in the same folder for more details.

2.3 Partition size[edit]

If you decide to change the size of some partition you need to change in the file android_layout.config.

You need to adapt all parameter that looks like

PART_<NAME> <PART_SIZE> <PART_NB> <PART_LABEL> <PART_SUFFIX> <PART_ENABLE>
NAME: name of the local variable (last partition MUST start with PART_LAST_)
PART_SIZE: as xxxMB or xxxKB or xxxGB
PART_NB: number of instances of partition (x1 or x2)
PART_LABEL: name of the partition label
PART_SUFFIX (optional): name of the suffix in case PART_NB equal x2 (_a/_b by default)
PART_ENABLE (optional): device for which the partition is only applicable (sd)

When this is done you also need to adapt every FlashLayout_*.tsv under device/stm/<STM32Series>/layout/programmer to match your changes.

For that purpose, you can use the script device/stm/<STM32Series>/script/layout/build_tsv.py.

3 Audio configuration[edit]

The configuration file audio.stm.xml is stored in device/stm/<STM32Series>/<BoardId>/media/audio

For more details please refer to How to change audio device for Android

4 Lights configuration[edit]

The configuration file lights.stm.xml is stored in device/stm/<STM32Series>/<BoardId>/lights

The target of this file is to associated the list of leds with the Android light IDs:

  • notifications
  • attention
  • backlight
  • keyboard
  • buttons
  • battery
  • bluetooth
  • wifi

First you have to identify the list of available leds (it's recommended to stubbed the list of lights adding device="stub").

Open a terminal on the device:

PC $> adb shell

Get the list of available labels:

Board $> ls /sys/class/leds/

In the device-tree associated to your device, you can check the list of <label> names in the <led> structure.

Then you can associate the following Android light IDs with the correct label.

5 Thermal configuration[edit]

The configuration file thermal.stm.xml is stored in device/stm/<STM32Series>/<BoardId>/thermal

Thermal information can be returned for the following list of temperature types:

  • CPUx (one index for each CPU)
  • GPU
  • Battery
  • Skin (external part of the device)

First you have to identify the list of available thermal zones (it's recommended to stubbed the list of thermal data adding stub="1" and adding fixed values for threshold,shutdown and threshold_vr_min).

Open a terminal on the device:

PC $> adb shell

Check the list of available zones:

Board $> ls /sys/class/thermal/

Check each thermal zone types (example with two thermal zones with indexes 0 and 1) :

Board $> cat /sys/class/thermal/thermal_zone0/type
Board $> cat /sys/class/thermal/thermal_zone1/type

You can check for each zone the list of trip point available (not systematically present, example with two trip points with indexes 0 and 1 for thermal zone 0):

Board $> cat /sys/class/thermal/thermal_zone0/trip_point_0_type
Board $> cat /sys/class/thermal/thermal_zone0/trip_point_1_type

From this stage, you can update in consequence the configuration file.

  • If no information is available, you can stubbed adding fixed values stub="1"
  • If a thermal zone is associated to one or several temperature types stub="0"
    • case without trip point data, you have to fixed the values in the file
    • case with trip point data, you have to put all data at 0 and add each trip index and type values in the file

6 Bluetooth configuration[edit]

The configuration is stored in bdroid_buildcfg.h located in device/stm/<STM32Series>/<BoardId>/network/bt.

The Bluetooth is enabled in device/stm/<STM32Series>/<BoardId>/BoardConfig.mk

BOARD_HAVE_BLUETOOTH := true
BOARD_HAVE_BLUETOOTH_LINUX := true

The path of the configuration file overlay bdroid_buildcfg.h must be also added:

BOARD_BLUETOOTH_BDROID_BUILDCFG_INCLUDE_DIR ?= device/stm/<STM32Series>/<BoardId>/network/bt

The Android Bluetooth stack (located in system/bt) can be configured thanks to the file device/stm/<STM32Series>/<BoardId>/network/bt/bdroid_buildcfg.h.

It must at least contain the definition of the Class of Device (CoD) (see more information in the Bluetooth Specification[1])

#define BTA_DM_COD {0x5A, 0x01, 0x1C}

Additionally, it can contain the Bluetooth Stack profile configuration. If a variable is not set in this file, the default configuration is selected in the stack.

By default, all the profiles are selected (see system/bt/include/bt_target.h). Example for the PAN profile:

#ifndef BTA_PAN_INCLUDED
#define BTA_PAN_INCLUDED TRUE
#endif

If you want to disable it, add the following line in bdroid_buildcfg.h:

#define BTA_PAN_INCLUDED FALSE

More details in Android Bluetooth[2].

7 Wi-Fi configuration[edit]

The configuration is stored in device/stm/<STM32Series>/<BoardId>/network/wifi.

You can change various configuration:

  • p2p
  • wpa supplicant
  • dhcp

For more details please refer to How to change Wi-Fi device for Android

8 Modify Android distribution[edit]

You can adapt the list of changes performed during the <STM32Series>setup (ex: stm32mp1setup for STM32MP1 series) modifying the file android_patch.config available in device/stm/<STM32Series>/patch/android/

For that purpose, before any modification, you have to clear the current configuration:

PC $> <STM32Series>clear -p

From this stage, you can adapt the file (add or/and remove list of commits and patches).

Some rules shall be followed for added patches:

  • Patch files shall be added with the relative path to device/stm/<STM32Series>/patch/android/ directory.
  • Patch files shall be added without the suffix .patch
  • Patch shall be added in the correct order

Some rules shall be followed for removed patches:

  • Test new configuration on the targeted directory applying patches manually (re-generate them if required)
  • Do not remove patches and commits with do not modify mention

Then you can apply the new configuration:

PC $> <STM32Series>setup

From this stage, you have to rebuild the distribution to take into account your changes:

PC $> make -j

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