As illustrated in the following example, a device driver stream handler implements function through two additional entry points: SHCEntryPoint and SHDEntryPoint.
Device driver stream handlers receive commands from the Sync/Stream Manager to initialize and perform streaming functions. These stream handler commands (SHCs) are accessible through a single entry point, SHCEntryPoint. The main routine is an IDC interface with the Sync/Stream Manager Device Driver. The SSM calls the device driver stream handler by issuing stream programming interface (SPI) functions such as SpiCreateStream, SpiStartStream, and SpiStopStream.
The following example illustrates the code implementation of the SHCEntryPoint.
RC DDCMDEntryPoint(PDDCMDCOMMON pCommon); /* PDD entry point from SH */
RC SHDEntryPoint(PSHD_COMMON pCommon); /* SH entry point from PDD */
RC SHCEntryPoint(PSHC_COMMON pCommon); /* SH entry point from SSM */
RC SMHEntryPoint(PSHC_COMMON pCommon); /* SSM entry point from SH */
ULONG (*ShcFuncs[])(PVOID pCommon) = { /* SHC function jump table */
SHCAssociate, /* 0 */
SHCClose, /* 1 */
SHCCreate, /* 2 */
SHCDestroy, /* 3 */
SHCStart, /* 4 */
SHCStop, /* 5 */
SHCSeek, /* 6 */
SHCEnableEvent, /* 7 */
SHCDisableEvent, /* 8 */
SHCEnableSync, /* 9 */
SHCDisableSync, /* 10 */
SHCGetTime, /* 11 */
SHCGetProtocol, /* 12 */
SHCInstallProtocol, /* 13 */
SHCEnumerateProtocols, /* 14 */
SHCNegotiateResult /* 15 */
};
USHORT MaxShcFuncs = sizeof(ShcFuncs)/sizeof(USHORT);
/**********************************************************************/
RC SHCEntryPoint(pCommon)
PSHC_COMMON pCommon;
{
if (pCommon->ulFunction > (ULONG)MaxShcFuncs)
return(ERROR_INVALID_FUNCTION);
/* Check for valid function */
return(ShcFuncs[pCommon->ulFunction](pCommon));
} /* Call SHC message */
/**********************************************************************/
RC SHCStart(PPARM_START pStart)
{
PSTREAM pSTREAM; /* Ptr to current stream */
DDCMDREADWRITE DDCMDReadWrite;
DDCMDCONTROL DDCMDControl;
ulRC rc; /* Return code */
if (rc = GetStreamEntry(&pSTREAM, pStart->hstream))
return(rc);
EnterCritSec; /* Disable interrupts */
switch (pSTREAM->ulStateFlg) {
case STREAM_RUNNING:
/*********************************************************/
/* Get a full buffer for playback */
/*********************************************************/
ParmNotify.ulFunction = SMH_NOTIFY;
ParmNotify.hid = pSTREAM->hid;
ParmNotify.hstream = pSTREAM->hStream;
ParmNotify.ulGetNumEntries = 1;
ParmNotify.ulRetNumEntries = 0;
ParmNotify.pGetBufTab = &(pSTREAM->BufTab.aBufTab[usBufTabIndex]);
ParmNotify.pRetBufTab = NULL;
ParmNotify.ulFlags = BUF_GETFULL;
SMHEntryPoint(&ParmNotify);
/**********************************************************/
/* Send full buffer to device (PDD) */
/**********************************************************/
DDCMDReadWrite.hStream = (*ppSTREAM)->hStream;
DDCMDReadWrite.ulFunction = DDCMD_WRITE;
DDCMDReadWrite.pBuffer = pCurrentBufTab->pBuffer;
DDCMDReadWrite.ulBufferSize = pCurrentBufTab->ulLength;
rc = (*pSTREAM->pDDCMDEntryPoint)(&DDCMDReadWrite);
/*********************************************************/
/* Start the device */
/*********************************************************/
DDCMDControl.ulFunction = DDCMD_CONTROL;
DDCMDControl.hStream = pSTREAM->hStream;
DDCMDControl.pParm = NULL;
DDCMDControl.ulParmSize = NULL;
DDCMDControl.ulCmd = DDCMD_START;
rc = (*pSTREAM->pDDCMDEntryPoint)(&DDCMDControl);
break;
}
ExitCritSec;
return(rc);
}