Editing Documentation/Maemo 5 Developer Guide/Architecture/System Software

* [[#System Control|System Control]] (SC)

* [[#Energy Management|Energy Management]] (EM) and  

* [[#Power Management|Power Management]] (PM).

System control subsystem is responsible for device state management (DSME), mode control (MCE) and various UI components including system UI, control panel applets and status bar icons. In addition, the system control subsystem includes HAL component for hardware abstraction, maemo-launcher for application startup execution, alarmd for alarm event handling, clockd for time management, iphbd for synchronization and profiled for profile handling. The SC subsystem provides D-Bus interface towards other applications. All the system control components are located in user space.

Energy management subsystem is responsible of battery charging. More specifically, the EM subsystem handles battery voltage monitoring and recognition, charging (via USB) and charger recognition. In addition, battery plugin for HAL is provided to provide standard D-Bus interface towards other applications. For example, the battery applet uses the HAL battery plugin to indicate the battery status in the UI. The EM subsystem components are located both in kernel and user space.

Power management subsystem is located entirely in kernel space. PM subsystem is responsible for putting the OMAP and peripherals into lowest possible power states as often as possible, without compromising performance. To achieve this, all the drivers in the system need to co-operate with the PM subsystem. The PM subsystem is build from standard linux kernel components including clock, CPUIdle and CPUFreq frameworks.

: Status Bar Battery plugin

: Provides battery status settings

;Description

: <ul><li>Provides status bar plugin to visualize battery status</li><li>Provides estimation for battery time left  for idle and use scenarios</li></ul>

;Name

: Control Panel Device Lock plugin

: Provides device lock settings

: Provides control panel plugin for<ul><li>autolock settings (on/off, period)</li><li>*lock code</li></ul><br/>Store the settings in DSM Gconf

DSME is responsible of device state management , process lifeguard support, watch dogs and thermal management. DSME architecture is based on modular plugin architecture. DSME core provides message handling capabilities to modules. Each module is dynamically loaded library. DSME runs in a single process. The D-Bus interface provides services to request reboot, shutdown or powerup (from acting dead mode), indication of shutdown, thermal events and data save.

{{ambox

|text=In Fremantle release onwards, DSME is not part of the initfs anymore. Instead, it is located in the rootfs and started after init.}}

: Mode Control Entity

;Purpose

: Provides device mode logic and services for DSM interface.

;Description

: <ul><li>Provides means for device mode control (Eg: flight mode)</li><li>Provides DSM gconf API for controlling display and security.</li><li>Manages DSM API for applications.</li></ul>

===Alarm Daemon (Alarmd)===

===Time Daemon (Clockd)===

===Profile Daemon (Profiled)===

===Heartbeat Daemon (Heartbeatd)===

 

{| class="wikitable"

|+ System control public interfaces

! Interface !! Purpose !! Interface type

| DSME API || Interface for requesting device powerup, shutdown and reboot. <br/>Interface for thermal management indications.

| D-Bus

| Dsmetool CLI || Interface for init scripts to start processes which will be monitored for system robustness.

| Socket

| HAL API || Provides device property information and events about device state changes.

| D-Bus or library (libhal)

| DSM GConf API || Interface for DSM related configuration values (security lock key, display)

| MCE API || Interface for requesting display control and lock status, device mode changes and status, inactivity status, and device lock mode and status.

| D-Bus  

| Profile API || Interface for requesting display control and lock status, device mode changes and status, inactivity status, and device lock mode and status.

| D-Bus  

| Time API || Control and notifications about timezone and time changes.

| D-Bus  

| [[Documentation/Maemo 5 Developer Guide/Using Generic Platform Components/Alarm Framework|Alarm API]] || Requesting, changing and deleting alarms.

| D-Bus  

| HeartBeat API || Getting heart beat on requested interval.

| Socket  

 

 

{| class="wikitable"

|+ Energy management public interfaces

! Interface !! Purpose !! Type

| Battery HAL API || Battery event API. Provides battery and charger status changes.

====Dynamic sleep====

 

====Dynamic Voltage and Frequency Scaling====

: Provides clock framework for HW clock management.

;Responsibilities

: <ul><li>Provides common means for turning HW clocks on and off.</li><li>Provides HW clock sanity checks and use counts.</li><li>Allows power management to probe HW clocks status.</li><li>Handles also clock and power domains, and wakeup and sleep dependencies.</li></ul>

: Provides mechanism for selecting and entering the deepest possible sleep state based on the constraints

: Provides mechanism for selecting and entering the lowest possible operating point based on the MPU and DSP loads.

;Responsibilities

:<ul><li> Monitor CPU and DSP load requirements.</li><li>Adjust CPU and DSP frequencies based on load.</li></ul>

{| class="wikitable"

|+ Power management public interfaces

| Contraints API || Interface for drivers for setting constraints on bandwidth and latency to control the target sleep states.