[usb] Reset endpoints without waiting for a new transfer to be enqueued

The current endpoint reset logic defers the reset until the caller
attempts to enqueue a new transfer to that endpoint.  This is
insufficient when dealing with endpoints behind a transaction
translator, since the transaction translator is a resource shared
between multiple endpoints.

We cannot reset the endpoint as part of the completion handling, since
that would introduce recursive calls to usb_poll().  Instead, we
add the endpoint to a list of halted endpoints, and perform the reset
on the next call to usb_step().

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/usb.h

@@ -380,11 +380,12 @@ struct usb_endpoint {
 
 	/** Endpoint is open */
 	int open;
-	/** Current failure state (if any) */
-	int rc;
 	/** Buffer fill level */
 	unsigned int fill;
 
+	/** List of halted endpoints */
+	struct list_head halted;
+
 	/** Host controller operations */
 	struct usb_endpoint_host_operations *host;
 	/** Host controller private data */
@@ -754,7 +755,7 @@ struct usb_port {
 	 */
 	struct usb_device *usb;
 	/** List of changed ports */
-	struct list_head list;
+	struct list_head changed;
 };
 
 /** A USB hub */
@@ -888,6 +889,8 @@ struct usb_bus {
 	struct list_head hubs;
 	/** List of changed ports */
 	struct list_head changed;
+	/** List of halted endpoints */
+	struct list_head halted;
 	/** Process */
 	struct process process;