diff --git a/include/gint/usb.h b/include/gint/usb.h
index 0ccc08f..ffffa3c 100644
--- a/include/gint/usb.h
+++ b/include/gint/usb.h
@@ -29,32 +29,32 @@ enum {
 	/* There are no interfaces */
 	USB_OPEN_NO_INTERFACE = 1,
 	/* There are more interfaces than supported (16) */
-	USB_OPEN_TOO_MANY_INTERFACES,
+	USB_OPEN_TOO_MANY_INTERFACES = -2,
 	/* There are not enough endpoint numbers for every interface, or there
 	   are not enough pipes to set them up */
-	USB_OPEN_TOO_MANY_ENDPOINTS,
+	USB_OPEN_TOO_MANY_ENDPOINTS = -3,
 	/* There is not enough FIFO memory to use the requested buffer sizes */
-	USB_OPEN_NOT_ENOUGH_MEMORY,
+	USB_OPEN_NOT_ENOUGH_MEMORY = -4,
 	/* Information is missing, such as buffer size for some endpoints */
-	USB_OPEN_MISSING_DATA,
+	USB_OPEN_MISSING_DATA = -5,
 	/* Invalid parameters: bad endpoint numbers, bad buffer sizes... */
-	USB_OPEN_INVALID_PARAMS,
+	USB_OPEN_INVALID_PARAMS = -6,
 	/* USB interfaces are already opened */
-	USB_OPEN_ALREADY_OPEN,
+	USB_OPEN_ALREADY_OPEN = -7,
+
+	/* General timeout for a sync_timeout call */
+	USB_TIMEOUT = -8,
+	/* This pipe is busy with another call */
+	USB_BUSY = -9,
 
-	/* This pipe is busy (returned by usb_write_async()) */
-	USB_WRITE_BUSY,
 	/* Both FIFO controllers are busy, none is available to transfer */
-	USB_WRITE_NOFIFO,
-	/* Timeout */
-	USB_WRITE_TIMEOUT,
-
-	/* This pipe is busy (returned by usb_commit_async()) */
-	USB_COMMIT_BUSY,
+	USB_WRITE_NOFIFO = -10,
 	/* This pipe has no ongoing transfer to commit */
-	USB_COMMIT_INACTIVE,
-	/* Timeout */
-	USB_COMMIT_TIMEOUT,
+	USB_COMMIT_INACTIVE = -11,
+	/* This pipe is currently not receiving any data */
+	USB_READ_IDLE = -12,
+	/* No FIFO controller is available */
+	USB_READ_NOFIFO = -13,
 };
 
 /* usb_open(): Open the USB link
diff --git a/src/usb/pipes.c b/src/usb/pipes.c
index 511b0f5..ffc5050 100644
--- a/src/usb/pipes.c
+++ b/src/usb/pipes.c
@@ -366,7 +366,7 @@ int usb_write_async(int pipe, void const *data, int size, bool use_dma,
 {
 	asyncio_op_t *t = &pipe_transfers[pipe];
 	if(asyncio_op_busy(t))
-		return USB_WRITE_BUSY;
+		return USB_BUSY;
 
 	/* If this if the first write of a series, find a controller. */
 	/* TODO: usb_write_async(): TOC/TOU race on controller being free */
@@ -401,17 +401,17 @@ int usb_write_sync_timeout(int pipe, void const *data, int size, bool use_dma,
 			break;
 		if(rc == USB_WRITE_NOFIFO)
 			USB_LOG("USB_WRITE_NOFIFO\n");
-		if(rc != USB_WRITE_BUSY)
+		if(rc != USB_BUSY)
 			return rc;
 		if(timeout_elapsed(timeout))
-			return USB_WRITE_TIMEOUT;
+			return USB_TIMEOUT;
 		sleep();
 	}
 
 	while(!flag)
 	{
 		if(timeout_elapsed(timeout))
-			return USB_WRITE_TIMEOUT;
+			return USB_TIMEOUT;
 		sleep();
 	}
 	return 0;
@@ -426,7 +426,7 @@ int usb_commit_async(int pipe, gint_call_t callback)
 {
 	asyncio_op_t *t = &pipe_transfers[pipe];
 	if(asyncio_op_busy(t))
-		return USB_COMMIT_BUSY;
+		return USB_BUSY;
 	if(t->type != ASYNCIO_WRITE || t->controller == NOF)
 		return USB_COMMIT_INACTIVE;
 
@@ -473,10 +473,10 @@ int usb_commit_sync_timeout(int pipe, timeout_t const *timeout)
 		int rc = usb_commit_async(pipe, GINT_CALL_SET(&flag));
 		if(rc == 0)
 			break;
-		if(rc != USB_COMMIT_BUSY)
+		if(rc != USB_BUSY)
 			return rc;
 		if(timeout_elapsed(timeout))
-			return USB_COMMIT_TIMEOUT;
+			return USB_TIMEOUT;
 		sleep();
 	}
 
@@ -484,7 +484,7 @@ int usb_commit_sync_timeout(int pipe, timeout_t const *timeout)
 	while(!flag)
 	{
 		if(timeout_elapsed(timeout))
-			return USB_COMMIT_TIMEOUT;
+			return USB_TIMEOUT;
 		sleep();
 	}
 	return 0;
@@ -495,7 +495,6 @@ void usb_commit_sync(int pipe)
 	usb_commit_sync_timeout(pipe, NULL);
 }
 
-/* usb_pipe_write_bemp(): Callback for the BEMP interrupt on a pipe */
 void usb_pipe_write_bemp(int pipe)
 {
 	asyncio_op_t *t = &pipe_transfers[pipe];