virtual net_result nrecv( LinkLayerAddress *addr, uint8_t *payload, size_t &length ) {
packet_addr_t dest;
packet_error_t pferror = recvFrame( handle, &dest, payload, length );
if( pferror != PACKET_NO_ERROR && pferror != PACKET_RECVTIMEOUT_ERROR ) return net_fatal;
if( pferror == PACKET_RECVTIMEOUT_ERROR ) return net_trfail;
*addr = LinkLayerAddress( dest.addr );
return net_succeed;
}
void NcpSpi::HandleRxFrame(void)
{
SpiFrame recvFrame(mReceiveFrame);
SpiFrame sendFrame(mSendFrame);
// Pass the received frame to base class to process.
HandleReceive(recvFrame.GetData(), recvFrame.GetHeaderDataLen());
// The order of operations below is important. We should clear
// the `mHandlingRxFrame` before checking `mTxState` and possibly
// preparing the next transaction. Note that the callback
// `SpiTransactionComplete()` can be invoked from ISR at any point.
//
// If we switch the order, we have the following race situation:
// We check `mTxState` and it is in `kTxStateSending`, so we skip
// preparing the transaction here. But before we set the
// `mHandlingRxFrame` to `false`, the `SpiTransactionComplete()`
// happens and prepares the next transaction and sets the accept
// length to zero on `mSendFrame` (since it assumes we are still
// handling the previous received frame).
mHandlingRxFrame = false;
// If tx state is in `kTxStateSending`, we wait for the callback
// `SpiTransactionComplete()` which will then set up everything
// and prepare the next transaction.
if (mTxState != kTxStateSending)
{
sendFrame.SetHeaderAcceptLen(kSpiBufferSize - kSpiHeaderSize);
otPlatSpiSlavePrepareTransaction(mEmptySendFrameFullAccept, kSpiHeaderSize, mReceiveFrame, kSpiBufferSize,
/* aRequestTrans */ false);
// No need to check the error status. Getting `OT_ERROR_BUSY`
// is OK as everything will be set up properly from callback when
// the current transaction is completed.
}
}
