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Device Settings Front Panel Display HAL Documentation

Acronyms, Terms and Abbreviations

  • DS - Device Settings
  • HAL - Hardware Abstraction Layer
  • API - Application Programming Interface
  • Caller - Any user of the interface via the APIs
  • FPD - Front Panel Display
  • LED - Light-Emitting Diode
  • CPU - Central Processing Unit
  • SoC - System-On-Chip

Description

The diagram below describes a high-level software architecture of the DS Front Panel Display stack.

%%{ init : { "theme" : "forest", "flowchart" : { "curve" : "linear" }}}%%
flowchart TD
y[Caller]<-->x[DEVICE SETTINGS FRONT PANEL DISPLAY HAL];
x[DEVICE SETTINGS FRONT PANEL DISPLAY HAL]<-->z[Front Panel SoC Driver];
style y fill:#99CCFF,stroke:#333,stroke-width:0.3px,align:left
style z fill:#fcc,stroke:#333,stroke-width:0.3px,align:left
style x fill:#9f9,stroke:#333,stroke-width:0.3px,align:left

This interface provides a set of APIs to facilitate communication to Front Panel LED Display SoC Drivers.

The brightness, color and text of Front Panel LEDs can be set or retrieved. This interface also provides API to enable or disable the specified discrete LED on the Front Panel Display.

Component Runtime Execution Requirements

This interface must adeptly manage resources to prevent issues like memory leaks and excessive utilization. It must also meet performance goals for response time, throughput, and resource use as per the platform's capabilities.

Failure to meet these requirements will likely result in undefined and unexpected behavior.

Initialization and Startup

Caller must initialize by calling dsFPInit() before calling any other APIs. Caller has complete control over the FPD.

Threading Model

This interface is not required to be thread safe. Any caller invoking the APIs must ensure calls are made in a thread safe manner.

Process Model

This interface is required to support a single instantiation with a single process.

Memory Model

This interface is not required to allocate any memory.

Power Management Requirements

The FPD HAL is not involved in the power management operation directly. However, the caller will initiate the change in LED as part of power management handling.

The caller is responsible for driving LED status in accordance with power mode change.

Asynchronous Notification Model

This interface is not required to have any asynchronous notification.

Blocking calls

This interface is not required to have any blocking calls. Synchronous calls must complete within a reasonable time period. Any call that can fail due to the lack of response from the connected device must have a timeout period and the function must return the relevant error code.

Internal Error Handling

All the APIs must return error synchronously as a return argument. HAL is responsible for handling system errors (e.g. out of memory) internally.

Persistence Model

There is no requirement for the interface to persist any setting information. Caller is responsible to persist any settings related to the HAL.

Non-functional requirements

Logging and debugging requirements

This interface is required to support DEBUG, INFO and ERROR messages. INFO and DEBUG must be disabled by default and enabled when required.

Memory and performance requirements

This interface is required to not cause excessive memory and CPU utilization.

Quality Control

  • This interface is required to perform static analysis, our preferred tool is Coverity.
  • Have a zero-warning policy with regards to compiling. All warnings are required to be treated as errors.
  • Copyright validation is required to be performed, e.g.: Black duck, and FossID.
  • Use of memory analysis tools like Valgrind are encouraged to identify leaks/corruptions.
  • HAL Tests will endeavour to create worst case scenarios to assist investigations.
  • Improvements by any party to the testing suite are required to be fed back.

Licensing

The HAL implementation is expected to released under the Apache License 2.0.

Build Requirements

The source code must build into a shared library for Device Settings HAL as FPD is a part of Device Settings and must be named as libdshal.so. The build mechanism must be independent of Yocto.

Variability Management

Any changes in the APIs must be reviewed and approved by the component architects. DS FPD must return the dsERR_OPERATION_NOT_SUPPORTED error code if any of the interface APIs are not supported by the underlying hardware.

Platform or Product Customization

The configuration settings file (dsFPDSettings.h) for DS Front Panel can be used for adding platform specific configurations. The sample file is available here.

Interface API Documentation

API documentation will be provided by Doxygen which will be generated from the header file.

Theory of operation and key concepts

The caller is expected to have complete control over the life cycle of the HAL.

  1. Initialize the FPD HAL using dsFPInit() before making any other API calls. If the init call fails, the HAL must return the respective error code, so that the caller can retry the operation.

  2. Once the FPD sub-system is initialized, caller can invoke APIs to control the Front Panel LEDs. The FP brightness, text, color, blink interval, FP LED state(ON/OFF), text scroll can be set or retrieved.

  3. De-initialize the FP HAL using dsFPTerm().

Note : The module would operate deterministically if the above call sequence is followed

The various DS FP LED states are as follows:

  • Active
  • Standby
  • Connecting to WPS
  • Connected to WPS
  • WPS Error
  • Factory Reset
  • USB Upgrade
  • Software Download Error

Diagrams

Operational Call Sequence

%%{ init : { "theme" : "default", "flowchart" : { "curve" : "stepBefore" }}}%%
   sequenceDiagram
    participant Caller as Caller
    participant HAL as DS FPD HAL
    participant Driver as SoC
    Caller->>HAL:dsFPInit()
    Note over HAL: SoC initializes the FPD subsystem
    HAL->>Driver: Allocates required resources for FPD
    Driver-->>HAL:return
    HAL-->>Caller:return
    Caller->>HAL: ds_FP_SetMethods
    Note over HAL: APIs to set the FPD Parameters
    HAL->>Driver:Sets the FPD Parameters
    Driver-->>HAL:return
    HAL-->>Caller:return
    Caller->>HAL: ds_FP_GetMethods
    Note over HAL: APIs to get the FPD Parameters
    HAL->>Driver:Gets the FPD Parameters
    Driver-->>HAL:return
    HAL-->>Caller:return
    Caller->>HAL:dsEnableClockDisplay()
    Note over HAL: API to enable or disable Clock Display on FP LED
    HAL->>Driver: Enables or Disables the clock display on the Front Panel LED
    Driver-->>HAL:return
    HAL-->>Caller:return
    Caller ->>HAL:dsFPTerm()
    HAL ->> Driver: Releases all the resources allocated during FPD init
    Driver-->>HAL:return
    HAL-->>Caller:return