usb_audio: Clean up buffer management.

* Get rid of fPacketSize and use fSamplesCount in GetBuffers instead.

 * Clarify logic in _TransferCallback.

 * Properly multiply in kSamplesBufferCount to fAreaSize
   (this should be the only functional change in here.)

The larger buffers (now similarly sized to HDA at least in the
default cases of 44100 or 48000) seem to help with jittering
and discontinuities, which are significantly reduced now,
at least under emulation.

src/add-ons/kernel/drivers/audio/usb/Stream.cpp

@@ -31,7 +31,6 @@ Stream::Stream(Device* device, size_t interface, usb_interface_list* List)
 	fCurrentBuffer(0),
 	fSamplesCount(0),
 	fStartingFrame(0),
-	fPacketSize(0),
 	fProcessedBuffers(0),
 	fInsideNotify(0)
 {
@@ -164,11 +163,11 @@ Stream::_SetupBuffers()
 	uint32 sampleSize = format->fNumChannels * format->fSubframeSize;
 
 	// data size pro 1 ms USB 1 frame or 1/8 ms USB 2 microframe
-	fPacketSize = samplingRate * sampleSize
+	size_t packetSize = samplingRate * sampleSize
 		/ (fDevice->fUSBVersion < 0x0200 ? 1000 : 8000);
-	TRACE(INF, "packetSize:%ld\n", fPacketSize);
+	TRACE(INF, "packetSize:%ld\n", packetSize);
 
-	if (fPacketSize == 0) {
+	if (packetSize == 0) {
 		TRACE(ERR, "computed packet size is 0!");
 		return B_BAD_VALUE;
 	}
@@ -180,7 +179,7 @@ Stream::_SetupBuffers()
 		delete fDescriptors;
 	}
 
-	fAreaSize = sampleSize * kSamplesBufferSize;
+	fAreaSize = sampleSize * kSamplesBufferSize * kSamplesBufferCount;
 	TRACE(INF, "estimate fAreaSize:%d\n", fAreaSize);
 
 	// round up to B_PAGE_SIZE and create area
@@ -210,19 +209,19 @@ Stream::_SetupBuffers()
 	TRACE(INF, "Created area id:%d at addr:%#010x size:%#010lx\n",
 		fArea, fDescriptors, fAreaSize);
 
-	fDescriptorsCount = fAreaSize / fPacketSize;
+	fDescriptorsCount = fAreaSize / packetSize;
 	// we need same size sub-buffers. round it
 	fDescriptorsCount = ROUNDDOWN(fDescriptorsCount, kSamplesBufferCount);
 	fDescriptors = new usb_iso_packet_descriptor[fDescriptorsCount];
 	TRACE(INF, "descriptorsCount:%d\n", fDescriptorsCount);
 
 	// samples count
-	fSamplesCount = fDescriptorsCount * fPacketSize / sampleSize;
+	fSamplesCount = fDescriptorsCount * packetSize / sampleSize;
 	TRACE(INF, "samplesCount:%d\n", fSamplesCount);
 
 	// initialize descriptors array
 	for (size_t i = 0; i < fDescriptorsCount; i++) {
-		fDescriptors[i].request_length = fPacketSize;
+		fDescriptors[i].request_length = packetSize;
 		fDescriptors[i].actual_length = 0;
 		fDescriptors[i].status = B_OK;
 	}
@@ -317,7 +316,7 @@ Stream::_QueueNextTransfer(size_t queuedBuffer, bool start)
 		Stream::_TransferCallback, this);
 
 	TRACE(DTA, "frame:%#010x\n", fStartingFrame);
-	return status; // B_OK;
+	return status;
 }
 
 
@@ -325,6 +324,8 @@ void
 Stream::_TransferCallback(void* cookie, status_t status, void* data,
 	size_t actualLength)
 {
+	TRACE(DTA, "st:%#010x, data:%#010x, len:%d\n", status, data, actualLength);
+
 	Stream* stream = (Stream*)cookie;
 	atomic_add(&stream->fInsideNotify, 1);
 	if (status == B_CANCELED || stream->fDevice->fRemoved || !stream->fIsRunning) {
@@ -334,18 +335,15 @@ Stream::_TransferCallback(void* cookie, status_t status, void* data,
 		return;
 	}
 
-	stream->fCurrentBuffer = (stream->fCurrentBuffer + 1) % kSamplesBufferCount;
-
 	stream->_DumpDescriptors();
 
-	/*status_t result =*/ stream->_QueueNextTransfer(stream->fCurrentBuffer, false);
-
 	if (atomic_add(&stream->fProcessedBuffers, 1) > (int32)kSamplesBufferCount)
 		TRACE(ERR, "Processed buffers overflow:%d\n", stream->fProcessedBuffers);
 
 	release_sem_etc(stream->fDevice->fBuffersReadySem, 1, B_DO_NOT_RESCHEDULE);
 
-	TRACE(DTA, "st:%#010x, data:%#010x, len:%d\n", status, data, actualLength);
+	stream->fCurrentBuffer = (stream->fCurrentBuffer + 1) % kSamplesBufferCount;
+	status = stream->_QueueNextTransfer(stream->fCurrentBuffer, false);
 
 	atomic_add(&stream->fInsideNotify, -1);
 }
@@ -498,13 +496,9 @@ Stream::GetBuffers(multi_buffer_list* List)
 			uint32 stride = format->fSubframeSize * format->fNumChannels;
 			descs[channel].stride = stride;
 
-			// init to buffers area begin
+			size_t bufferSize = (fSamplesCount / kSamplesBufferCount) * stride;
 			descs[channel].base = (char*)fBuffers;
-			// shift for whole buffer if required
-			size_t bufferSize = fPacketSize
-				* (fDescriptorsCount / kSamplesBufferCount);
 			descs[channel].base += buffer * bufferSize;
-			// shift for channel if required
 			descs[channel].base += channel * format->fSubframeSize;
 
 			TRACE(DTA, "%d:%d: base:%#010x; stride:%#010x\n", buffer, channel,

src/add-ons/kernel/drivers/audio/usb/Stream.h

@@ -58,7 +58,6 @@ protected:
 			size_t			fCurrentBuffer;
 			size_t			fSamplesCount;
 
-			size_t			fPacketSize;
 			uint32			fStartingFrame;
 			int32			fProcessedBuffers;
 			int32			fInsideNotify;