引用 1 楼 guopeixin 的回复: 1。host通过初始化时候注册的api直接调用bus； 2。而bus通过bus层类的基类直接调用host，同样是在host初始化的时候注册

引用 19 楼 so927 的回复: PLATFORM\COMMON\SRC\COMMON\OTHER\memory.c 中有 BOOL OEMGetExtensionDRAM(LPDWORD pMemoryStart, LPDWORD pMemoryLength) { ? ? return FALSE; } 没有代码，直接返回了FALSE 我在PLATFORM\DEVICEEMULATOR\SRC\OAL\OALLIB\init.c中找到了一个此函数的实现代码 C/C++ codeBOOL OEMGetExtensionDRAM(     LPDWORD lpMemStart,     LPDWORD lpMemLen     ) {     typedefvolatile unsignedlong MegOfExtendedRam_t[1024*1024/sizeof (unsignedlong)];     MegOfExtendedRam_t*MegsOfRam= (MegOfExtendedRam_t*)EXTENDED_RAM_BASE;     DWORD each_meg;const DWORD dwPageSize=4096;// PAGE_SIZE in ceddk isn't valid until later in boot     OALMSG(OAL_FUNC, (L"++OEMGetExtensionDRAM\r\n"));// Employ a simple memory test to see that all N meg's are there.// NB: Because an empty memory bus can "float" data for several// cycles and appear as valid memory, discharge the bus before// verifying the data.//// The probe is nondestructive, to allow the contents of extension// RAM to be preserved across soft resetstry {for (each_meg=0; each_meg< EXTENDED_RAM_MEGS;++each_meg)         {             unsignedlong temp0= MegsOfRam[each_meg][0];             unsignedlong temp1= MegsOfRam[each_meg][1];             MegsOfRam[each_meg][0]=0x55555555UL;// Write pattern            MegsOfRam[each_meg][1]=~0x55555555UL;// Dischargeif (MegsOfRam[each_meg][0]!=0x55555555UL)// Verify paternbreak;             MegsOfRam[each_meg][0]=~0x55555555UL;// Write pattern-not            MegsOfRam[each_meg][1]=0x55555555UL;// Dischargeif (MegsOfRam[each_meg][0]!=~0x55555555UL)break;             MegsOfRam[each_meg][0]= temp0;             MegsOfRam[each_meg][1]= temp1;         }     } except (EXCEPTION_EXECUTE_HANDLER) {         OALMSG(OAL_FUNC, (L"--OEMGetExtensionDRAM\r\n"));return FALSE;// no extension DRAM    }*lpMemStart= EXTENDED_RAM_BASE;*lpMemLen= each_meg*sizeof (MegOfExtendedRam_t);     OALMSG(OAL_LOG_INFO, (L"OEMGetExtensionDRAM: found 0x%08x bytes of ram at 0x%08x\r\n",*lpMemLen,*lpMemStart));// adjust by RAM FMD amountif(g_dwExtensionRAMFMDSize!=0) {if((g_dwExtensionRAMFMDSize& (dwPageSize-1))!=0) {             OALMSG(OAL_LOG_WARN,                 (L"OEMGetExtensionDRAM: g_dwExtensionRAMFMDSize 0x%08x not a multiple of %u\r\n",                 g_dwExtensionRAMFMDSize, dwPageSize));         }elseif(*lpMemLen< g_dwExtensionRAMFMDSize) {             OALMSG(OAL_LOG_WARN,                 (L"OEMGetExtensionDRAM: 0x%08x bytes of extension ram not enough to satisfy FMD request for 0x%0x bytes\r\n",*lpMemLen, g_dwExtensionRAMFMDSize));         }else {             g_pvExtensionRAMFMDBaseAddr= (PVOID) EXTENDED_RAM_BASE;*lpMemStart= EXTENDED_RAM_BASE+ g_dwExtensionRAMFMDSize;*lpMemLen-= g_dwExtensionRAMFMDSize;                 OALMSG(OAL_LOG_INFO, (L"OEMGetExtensionDRAM: reserving 0x%08x bytes of ram at 0x%08x for RAMFMD\r\n",                     g_dwExtensionRAMFMDSize, g_pvExtensionRAMFMDBaseAddr));         }     }     OALMSG(OAL_LOG_INFO, (L"OEMGetExtensionDRAM: returning 0x%08x bytes of ram at 0x%08x\r\n",*lpMemLen,*lpMemStart));     OALMSG(OAL_FUNC, (L"--OEMGetExtensionDRAM\r\n"));return TRUE; } 有点搞不明白了