Android Telephony Radio Layer Interface _telephone-radio唤醒

Radio Layer Interface

Introduction
RIL Initialization
RIL Interaction

Solicited
Unsolicited

Implementing the RIL

RIL_Init

RIL Functions

RIL Solicited Command Requests
RIL Unsolicited Commands

Introduction

Android's Radio Interface Layer (RIL) provides an abstraction layer between Android telephony services (android.telephony ) and radio hardware. The RIL is radio agnostic, and includes support for Global System for Mobile communication (GSM)-based radios. 

The diagram below illustrates the RIL in the context of Android's Telephony system architecture.

Solid elements represent Android blocks and dashed elements represent partner-specific proprietary blocks.

The RIL consists of two primary components:

• RIL Daemon : The RIL daemon initializes the Vendor RIL, processes all communication from Android telephony services, and dispatches calls to the Vendor RIL as solicited commands.
• Vendor RIL : The radio-specific Vendor RIL of ril.h that processes all communication with radio hardware and dispatches calls to the RIL Daemon (rild ) through unsolicited commands.

RIL Initialization

Android initializes the telephony stack and the Vendor RIL at startup as described in the sequence below:

1. RIL daemon reads rild.lib path and rild.libargs system properties to determine the Vendor RIL library to use and any initialization arguments to provide to the Vendor RIL
2. RIL daemon loads the Vendor RIL library and calls RIL_Init to initialize the RIL and obtain a reference to RIL functions
3. RIL daemon calls RIL_register on the Android telephony stack, providing a reference to the Vendor RIL functions

See the RIL Daemon source code at //device/commands/rild/rild.c for details.

RIL Interaction

There are two forms of communication that the RIL handles:

• Solicited commands: Solicited commands originated by RIL lib, such as DIAL and HANGUP .
• Unsolicited responses: Unsolicited responses that originate from the baseband, such as CALL_STATE_CHANGED and NEW_SMS .

Solicited

The following snippet illustrates the interface for solicited commands:

void OnRequest (int request_id, void *data, size_t datalen, RIL_Token t);

void OnRequestComplete (RIL_Token t, RIL_Error e, void *response, size_t responselen);

There are over sixty solicited commands grouped by the following families:

• SIM PIN, IO, and IMSI/IMEI (11)
• Call status and handling (dial, answer, mute…) (16)
• Network status query (4)
• Network setting (barring, forwarding, selection…) (12)
• SMS (3)
• PDP connection (4)
• Power and reset (2)
• Supplementary Services (5)
• Vendor defined and support (4)

The following diagram illustrates a solicited call in Android.

Unsolicited

The following snippet illustrates the interface for unsolicited commands:

void OnUnsolicitedResponse (int unsolResponse, void *data, size_t datalen);

There are over ten unsolicited commands grouped by the following families:

• Network status changed (4)
• New SMS notify (3)
• New USSD notify (2)
• Signal strength or time changed (2)

The following diagram illustrates an unsolicited call in Android.

Implementing the RIL

To implement a radio-specific RIL, create a shared library that implements a set of functions required by Android to process radio requests. The required functions are defined in the RIL header (/include/telephony/ril.h ).

The Android radio interface is radio-agnostic and the Vendor RIL can use any protocol to communicate with the radio. Android provides a reference Vendor RIL, using the Hayes AT command set, that you can use as a quick start for telephony testing and a guide for commercial vendor RILs. The source code for the reference RIL is found at /commands/reference-ril/ .

Compile your Vendor RIL as a shared library using the convention libril-<companyname>-<RIL version>.so , for example, libril-acme-124.so, where:

• libril : all vendor RIL implementations start with 'libril'
• <companyname> : a company-specific abbreviation
• <RIL version> : RIL version number
• so : file extension

RIL_Init

Your Vendor RIL must define a RIL_Init function that provides a handle to the functions which will process all radio requests. RIL_Init will be called by the Android RIL Daemon at boot time to initialize the RIL.

RIL_RadioFunctions *RIL_Init (RIL_Env* env, int argc, char **argv);

RIL_Init should return a RIL_RadioFunctions structure containing the handles to the radio functions:

type structure {

        
int RIL_version;

        
RIL_RequestFunc onRequest;

        
RIL_RadioStateRequest onStateRequest;      

        
RIL_Supports supports;

        
RIL_Cancel onCancel;

        
RIL_GetVersion getVersion;

} 

RIL_RadioFunctions;

RIL Functions

ril.h defines RIL states and variables, such as RIL_UNSOL_STK_CALL_SETUP , RIL_SIM_READY , RIL_SIM_NOT_READY , as well as the functions described in the tables below. Skim the header file (/device/include/telephony/ril.h ) for details.

RIL Solicited Command Requests

The vendor RIL must provide the functions described in the table below to handle solicited commands. The RIL solicited command request types are defined in ril.h with the RIL_REQUEST_ prefix. Check the header file for details.

The vendor RIL uses the following callback methods to communicate back to the Android RIL daemon.

RIL Unsolicited Commands

The functions listed in the table below are call-back functions used by the Vendor RIL to invoke unsolicited commands on the Android platform. See ril.h for details.