NVRAM讀寫操作詳解在MTK中，NVRAM是作為一個獨立的task來運行的。在nvram_main.c文件中，(代碼有刪減,注釋部分用黃色標出,便于閱讀)voidnvram_task_main(task_entry_struct*task_entry_ptr){kal_get_my_task_index(&my_index);/*nvramspecialservice*/nvram_special_service();while(1){//從Q中得到消息receive_msg_ext_q(task_info_g[task_entry_ptr->task_indx].task_ext_qid,¤t_ilm);stack_set_active_module_id(my_index,current_ilm.dest_mod_id); //處理消息nvram_main(¤t_ilm); //釋放消息free_ilm(¤t_ilm);}}Nvram_main函數,處理NVRAM相關的消息voidnvram_main(ilm_struct*ilm_ptr){if(ilm_ptr!=NULL){if((ilm_ptr->msg_id>=MSG_ID_NVRAM_CODE_BEGIN)&&(ilm_ptr->msg_id<=MSG_ID_NVRAM_CODE_END)){if(ilm_ptr->msg_id==MSG_ID_NVRAM_STARTUP_REQ){ //STARTUP消息nvram_startup_handler(ilm_ptr);}elseif(ilm_ptr->msg_id==MSG_ID_NVRAM_RESET_REQ){ //RESET消息nvram_reset_handler(ilm_ptr);}elseif(ilm_ptr->msg_id==MSG_ID_NVRAM_READ_REQ){ nvram_read_handler(ilm_ptr); //READ消息}elseif(ilm_ptr->msg_id==MSG_ID_NVRAM_WRITE_REQ){nvram_write_handler(ilm_ptr);//WRITE消息}elseif(ilm_ptr->msg_id==MSG_ID_NVRAM_SET_LOCK_REQ){nvram_set_lock_handler(ilm_ptr);//LOCK消息,比較多用在TST中}}}/*endofmodulemainfunction*/也可以看到NVRAMtask處理幾個消息.READ流程從NV中讀取一個數據,例如讀取語言設置信息:ReadValue(NVRAM_SETTING_LANG,&data,DS_BYTE,&error);我們需要注明,NVRAM的LID,讀取數據存放的指針,數據類型,和返回錯誤信息的地址.#defineReadValue(nId,pBuffer,nDataType,pError)\ReadValueInt(nId,pBuffer,nDataType,pError,__FILE__,__LINE__)ReadValue精簡了兩個參數,不需要注明文件和第多少行,方面了應用使用.看一下ReadValueInt這個函數.我們來看看這個函數到底干了什么事情:S32ReadValueInt(U8nDataItemId,void*pBuffer,U8nDataType,S16*pError,S8*fileName,S32lineNumber){switch(nDataType){caseDS_BYTE:{ //byteDataReadFlag先記住這個標志,它標志了byte的數據是否已經被讀取,所以從這里我們可以猜測,NVRAM的數據,應該不是每次都從硬件讀取的,而是有緩存的(記住這個假設,稍后驗證)/*secondtimereading,italwasyreturnonerequestitem*/if(byteDataReadFlag){ //這個注釋就更加明白了/*DataiscachednoneedtoreadfromNVRAM*/memcpy(pBuffer,&byte_data[nDataItemId*nDataType],nDataType);status=DS_BYTE;error=NVRAM_READ_SUCCESS;}/*processfirsttimereadingalldataandreturnfirstrequestitemdata*/else{/*ReaddatafromtheNVRAMfile*/ //這才從NVRAM文件中讀取 //這個BUFFER的大小,8*512=4KU8tempBuffer[NVRAM_CACHE_SIZE]; //這個函數重點分析status=ReadRecordInt(NVRAM_EF_CACHE_BYTE_LID,1,tempBuffer,sizeof(tempBuffer),&error,fileName,lineNumber);/*copyoutalltotalreadingdata*/ //把讀取的數據copy到byte_data里面去memcpy(byte_data,tempBuffer,sizeof(tempBuffer)); //這個時候把這個flag置上了byteDataReadFlag=1;/*returnfirstrequestitemdata*/memcpy(pBuffer,&byte_data[nDataItemId*nDataType],nDataType);status=DS_BYTE;error=NVRAM_READ_SUCCESS;}break;}/*EndofcaseDS_BYTE*///后面的SHORT,DOUBLE同樣道理caseDS_SHORT:{}/*EndofcaseDS_SHORT*/caseDS_DOUBLE:{}/*EndofcaseDS_DOUBLE*/}*pError=error;returnstatus;}ReadValueInt總結:這個函數,就是把以前讀好的三個數組的數據拿出來,如果還沒有從NVRAM讀取到cashe里面,就讀一次.關鍵的函數是:ReadRecordInt.第一次讀BYTE類型的數據之前,三個數組都是空的,flag也是空的,讀一個之后,byte數據被從NVRAM文件中讀入到cashe中,放在byte的數組里面,byteflag也被置上了.下次再讀的byte,就只需要從CACHE中讀取就可以了.同理,short和double數據也相同.來看看它是怎么做的#defineReadRecordInt(nFileId,nRecordId,pBuffer,nBufferSize,pError,fileName,lineNumber)\AccessRecordInt(nFileId,nRecordId,pBuffer,nBufferSize,1,pError,MMI_FALSE,MMI_TRUE,fileName,lineNumber)S32AccessRecordInt(U16nFileId,U16nRecordId,void*pBuffer,U16nBufferSize,U16nRecordAmount,S16*pError,pBOOLisWrite,pBOOLisValue,S8*filename,S32lineNumber){MYQUEUEqueueNode;S32status=-1;U32my_index;circularQ_check_enumcircularQ_check_result=circularQ_check_never_check;staticU8nvram_req_count=0;MMI_BOOLtoPush;if(isWrite){//WRITE的先放一下,先看READ的再說}else{ //發了一個消息 SendNVRAMReadReq(nFileId,nRecordId,nRecordAmount);//這個函數調用了Message.oslMsgId=MSG_ID_MMI_EQ_NVRAM_READ_REQ;//OslMsgSendExtQueue(&Message),發了一個REQ消息到Q上去.}in_nvram_procedure++;//REQ消息發完了,接下來就等RSP消息來while(1){/*ifmorethan1accessrequestexist,gothroughthecircularQ*/if((nvram_req_count>0)&&(circularQ_check_result==circularQ_check_never_check)){circularQ_check_result=NVRAMCheckCircularQ(&queueNode,nFileId);}if(circularQ_check_result!=circularQ_check_found){OslReceiveMsgExtQ(mmi_ext_qid,&queueNode);OslGetMyTaskIndex(&my_index);OslStackSetActiveModuleID(my_index,MOD_MMI);}//這個標志位先置空,不管,先記住它toPush=MMI_FALSE;switch(queueNode.msg_id){//這里列出了很多消息,其他不管,先找READ_RSP消息再說caseMSG_ID_MMI_EQ_PLAY_AUDIO_RSP:caseMSG_ID_MMI_EQ_STOP_AUDIO_RSP:caseMSG_ID_MMI_EQ_EXE_GPIO_LEVEL_RSP:caseMSG_ID_MMI_EQ_SET_VOLUME_RSP:caseMSG_ID_MMI_EQ_KEYPAD_DETECT_IND:caseMSG_ID_TIMER_EXPIRY://就它了caseMSG_ID_MMI_EQ_NVRAM_READ_RSP:{mmi_eq_nvram_read_rsp_struct*readMessage;readMessage=(mmi_eq_nvram_read_rsp_struct*)queueNode.oslDataPtr;{if(readMessage->result.flag==MMI_OK){ //讀成功了,再比較一下數據大小是不是合格if(readMessage->length>nBufferSize){}elseif(readMessage->length<nBufferSize){}else{memcpy(pBuffer,readMessage->data,readMessage->length);*pError=NVRAM_READ_SUCCESS;}status=readMessage->length;}OslFreeInterTaskMsg(&queueNode);}toPush=MMI_TRUE;break;}caseMSG_ID_MMI_EQ_NVRAM_WRITE_RSP:}//這個flag標志是否讀取成功if(toPush==MMI_TRUE){ilm_structilm_ptr;flag=OslWriteCircularQ(&ilm_ptr);OslFreeInterTaskMsg(&queueNode);}}}AccessRecordInt總結:這個函數是個真正的讀取函數,發REQ消息給NVRAMTASK,等待RSP消息,得到讀取數據.寫入流程重點分析WriteValueInt這個函數S32WriteValueInt(U8nDataItemId,void*pBuffer,U8nDataType,S16*pError,S8*fileName,S32lineNumber){switch(nDataType){//還拿BYTE來說caseDS_BYTE:{ //已經從NVRAM到CACHE里面了/*secondtimeaccess,italwayssetstherequestitem*/if(byteDataReadFlag){/*DataiscachednoneedtoreadfromNVRAM*/memcpy(&byte_data[nDataItemId*nDataType],pBuffer,nDataType);/*writeintoNVRAMmodule,ifnotwaitforfalshingdirectly*/if(!byteDataWriteFlashFlag){status=WriteRecordInt(NVRAM_EF_CACHE_BYTE_LID,1,byte_data,NVRAM_CACHE_SIZE,&error,fileName,lineNumber);}status=DS_BYTE;error=NVRAM_WRITE_SUCCESS;} //還沒有讀到CACHE里面/*processfirsttimeaccessalldataandreturnfirstwriteitemdata*/else{ //那就讀到CACHE/*ReadalldatafromtheNVRAMfile*/status=ReadRecordInt(NVRAM_EF_CACHE_BYTE_LID,1,byte_data,NVRAM_CACHE_SIZE,&error,fileName,lineNumber);memcpy(&byte_data[nDataItemId*nDataType],pBuffer,nDataType); //讀好了,就寫吧/*writeintoNVRAMmodule,ifnotwaitforfalshingdirectly*/if(!byteDataWriteFlashFlag){ //關鍵還是WriteRecordIntstatus=WriteRecordInt(NVRAM_EF_CACHE_BYTE_LID,1,byte_data,NVRAM_CACHE_SIZE,