drv: wait for any drivers to be added before trying to match iface

drvBind races with drvAdd. This change ensures that devices won't be
orphaned if added by hcd before adding the corresponding driver in the
single-driver scenario. This does not fix the race in case of
multi-driver scenario, though, hence the "orphaned" todo is left
untouched

JIRA: RTOS-937

usb/drv.c

@@ -29,6 +29,7 @@
 struct {
 	handle_t lock;
 	usb_drv_t *drvs;
+	handle_t drvAddedCond;
 } usbdrv_common;
 
 
@@ -251,11 +252,10 @@ static usb_drv_t *usb_drvMatchIface(usb_dev_t *dev, usb_iface_t *iface)
 	int i, match, bestmatch = 0;
 
 	mutexLock(usbdrv_common.lock);
-	drv = usbdrv_common.drvs;
-	if (drv == NULL) {
-		mutexUnlock(usbdrv_common.lock);
-		return NULL;
+	while (usbdrv_common.drvs == NULL) {
+		condWait(usbdrv_common.drvAddedCond, usbdrv_common.lock, 0);
 	}
+	drv = usbdrv_common.drvs;
 
 	do {
 		for (i = 0; i < drv->nfilters; i++) {
@@ -363,6 +363,9 @@ int usb_drvBind(usb_dev_t *dev)
 	umsg->insertion.descriptor = dev->desc;
 	umsg->insertion.locationID = dev->locationID;
 
+	/* FIXME: drvAdd races with drvMatchIface in multi-driver scenario.
+	 * Devices may become orphaned forever if they get added by hcd before the driver
+	 * is connected */
 	for (i = 0; i < dev->nifs; i++) {
 		if ((drv = usb_drvMatchIface(dev, &dev->ifs[i])) != NULL) {
 			dev->ifs[i].driver = drv;
@@ -417,6 +420,7 @@ void usb_drvAdd(usb_drv_t *drv)
 	idtree_init(&drv->pipes);
 	idtree_init(&drv->urbs);
 	LIST_ADD(&usbdrv_common.drvs, drv);
+	condSignal(usbdrv_common.drvAddedCond);
 	mutexUnlock(usbdrv_common.lock);
 }
 
@@ -617,10 +621,19 @@ void usb_drvPipeFree(usb_drv_t *drv, usb_pipe_t *pipe)
 
 int usb_drvInit(void)
 {
-	if (mutexCreate(&usbdrv_common.lock) != 0) {
+	int ret;
+
+	ret = mutexCreate(&usbdrv_common.lock);
+	if (ret != 0) {
 		USB_LOG("usbdrv: Can't create mutex!\n");
 		return -ENOMEM;
 	}
 
+	ret = condCreate(&usbdrv_common.drvAddedCond);
+	if (ret != 0) {
+		USB_LOG("usbdrv: Can't create cond!\n");
+		return -ENOMEM;
+	}
+
 	return 0;
 }