virtio_scsi: now handles events like capacity data changed.

* push event requests on the event queue, handles them.
* activate feature VIRTIO_SCSI_F_CHANGE.
* when a capacity data changed event is received, schedule a rescan of the scsi device node
on the scsi dpc queue. we find out unique child node and call the rescan_node() hook.
* Haiku only handles media changed events on removable devices, so the feature
only actually works when the device is defined as such, aka for QEMU the following option:
-device scsi-hd,drive=hd,removable=true

src/add-ons/kernel/busses/scsi/virtio/VirtioSCSIController.cpp

@@ -32,13 +32,17 @@ VirtioSCSIController::VirtioSCSIController(device_node *node)
 	fVirtio(NULL),
 	fVirtioDevice(NULL),
 	fStatus(B_NO_INIT),
-	fRequest(NULL)
+	fRequest(NULL),
+	fEventDPC(NULL)
 {
 	CALLED();
 
 	B_INITIALIZE_SPINLOCK(&fInterruptLock);
 	fInterruptCondition.Init(this, "virtio scsi transfer");
 
+	if (gSCSI->alloc_dpc(&fEventDPC) != B_OK)
+		return;
+	
 	// get the Virtio device from our parent's parent
 	device_node *parent = gDeviceManager->get_parent_node(node);
 	device_node *virtioParent = gDeviceManager->get_parent_node(parent);
@@ -49,7 +53,7 @@ VirtioSCSIController::VirtioSCSIController(device_node *node)
 	gDeviceManager->put_node(virtioParent);
 
 	fVirtio->negociate_features(fVirtioDevice,
-		0 /*VIRTIO_SCSI_F_HOTPLUG*/,
+		VIRTIO_SCSI_F_CHANGE /*VIRTIO_SCSI_F_HOTPLUG*/,
 		&fFeatures, &get_feature_name);
 
 	fStatus = fVirtio->read_device_config(fVirtioDevice, 0, &fConfig,
@@ -84,6 +88,9 @@ VirtioSCSIController::VirtioSCSIController(device_node *node)
 	fEventVirtioQueue = virtioQueues[1];
 	fRequestVirtioQueue = virtioQueues[2];
 
+	for (uint32 i = 0; i < VIRTIO_SCSI_NUM_EVENTS; i++)
+		_SubmitEvent(i);
+	
 	fStatus = fVirtio->setup_interrupt(fVirtioDevice, NULL, this);
 	if (fStatus != B_OK) {
 		ERROR("interrupt setup failed (%s)\n", strerror(fStatus));
@@ -98,6 +105,8 @@ VirtioSCSIController::~VirtioSCSIController()
 {
 	CALLED();
 	delete fRequest;
+
+	gSCSI->free_dpc(fEventDPC);
 }
 
 
@@ -262,3 +271,81 @@ VirtioSCSIController::_RequestInterrupt()
 	fInterruptCondition.NotifyAll();
 }
 
+
+
+void
+VirtioSCSIController::_EventCallback(void* driverCookie, void* cookie)
+{
+	CALLED();
+	VirtioSCSIController* controller = (VirtioSCSIController*)driverCookie;
+	struct virtio_scsi_event* event = (struct virtio_scsi_event*)cookie;
+	controller->_EventInterrupt(event);
+}
+
+
+void
+VirtioSCSIController::_EventInterrupt(struct virtio_scsi_event* event)
+{
+	CALLED();
+	TRACE("events %#x\n", event->event);
+	if ((event->event & VIRTIO_SCSI_T_EVENTS_MISSED) != 0) {
+		ERROR("events missed\n");
+	} else switch (event->event) {
+		case VIRTIO_SCSI_T_TRANSPORT_RESET:
+			ERROR("transport reset\n");
+			break;		
+		case VIRTIO_SCSI_T_ASYNC_NOTIFY:
+			ERROR("async notify\n");
+			break;
+		case VIRTIO_SCSI_T_PARAM_CHANGE:
+		{
+			uint16 sense = (event->reason >> 8)
+				| ((event->reason & 0xff) << 8);
+			if (sense == SCSIS_ASC_CAPACITY_DATA_HAS_CHANGED) {
+				ERROR("capacity data has changed for %x:%x\n", event->lun[1],
+					event->lun[2] << 8 | event->lun[3]);
+				gSCSI->schedule_dpc(fBus, fEventDPC, _RescanChildBus, this);
+			} else
+				ERROR("param change, unknown reason\n");
+			break;
+		}
+		default:
+			ERROR("unknown event %#x\n", event->event);
+			break;
+	}
+}
+
+
+void
+VirtioSCSIController::_SubmitEvent(uint32 eventNumber)
+{
+	CALLED();
+	struct virtio_scsi_event* event = &fEventBuffers[eventNumber];
+	bzero(event, sizeof(struct virtio_scsi_event));
+
+	physical_entry entry;
+	get_memory_map(event, sizeof(struct virtio_scsi_event), &entry, 1);
+
+	fVirtio->queue_request_v(fEventVirtioQueue, &entry,
+		0, 1, VirtioSCSIController::_EventCallback, event);
+}
+
+
+void
+VirtioSCSIController::_RescanChildBus(void *cookie)
+{
+	CALLED();
+	VirtioSCSIController* controller = (VirtioSCSIController*)cookie;
+	device_node *childNode = NULL;
+	const device_attr attrs[] = { { NULL } };
+	if (gDeviceManager->get_next_child_node(controller->fNode, attrs,
+		&childNode) != B_OK) {
+		ERROR("couldn't find the child node for %p\n", controller->fNode);
+		return;
+	}
+
+	gDeviceManager->rescan_node(childNode);
+	TRACE("rescan done %p\n", childNode);
+	gDeviceManager->put_node(childNode);
+}
+

src/add-ons/kernel/busses/scsi/virtio/VirtioSCSIPrivate.h

@@ -35,6 +35,8 @@ void swap_words(void *data, size_t size);
 #define VIRTIO_SCSI_STANDARD_TIMEOUT		10 * 1000 * 1000
 #define VIRTIO_SCSI_INITIATOR_ID	7
 
+#define VIRTIO_SCSI_NUM_EVENTS		4
+
 
 class VirtioSCSIRequest;
 
@@ -63,6 +65,11 @@ private:
 	static	void				_RequestCallback(void* driverCookie,
 									void *cookie);
 			void				_RequestInterrupt();
+	static	void				_EventCallback(void *driverCookie, void *cookie);
+			void				_EventInterrupt(struct virtio_scsi_event* event);
+	static	void				_RescanChildBus(void *cookie);
+
+			void				_SubmitEvent(uint32 event);
 
 			device_node*		fNode;
 			scsi_bus 			fBus;
@@ -87,6 +94,8 @@ private:
 			ConditionVariableEntry fInterruptConditionEntry;
 			bool				fExpectsInterrupt;
 
+			scsi_dpc_cookie		fEventDPC;
+			struct virtio_scsi_event fEventBuffers[VIRTIO_SCSI_NUM_EVENTS];
 };