usbdump: comments update

And I was wondering why the interrupt packets in dev-hid.c had a
reversed type marking...

1 files changed, 20 insertions, 2 deletions

diff --git a/hw/usb/dump.h b/hw/usb/dump.h
index a54bc5862d..247016f259 100644
--- a/hw/usb/dump.h
+++ b/hw/usb/dump.h
@@ -54,9 +54,27 @@ typedef struct UsbDumpState UsbDumpState;
  * - setup(setup_len == 0, OUT) / status(OUT) (BROKEN!)
  *
  * handle_data is called for all non-EP0 transfers. PID is either IN or OUT.
- * Sequence for the PID cases:
- * - IN: submit(); make data; complete(data); usb_packet_copy(data)
+ * Sequence for the PID cases (interrupt):
+ * - IN: make data; complete(data); usb_packet_copy(data); submit()
  * - OUT: usb_packet_copy(data); submit(data); process data; complete()
+ *
+ * If there is no data for IN, just return NAK without dumping to avoid log
+ * flood (due to the periodic polling by interrupts and isoc).
+ * Isoc has probably the same sequence as interrupt; bulk less so.
+ * In the IN sequence, note that complete(data) is called before submit. See the
+ * below diagram for the reason.
+ *             ___________
+ *       _____ \ ev_type /
+ *      | dir \ | S | C |
+ *      |       +---+---+
+ *      |  IN   | n | y | (whether the packet has data for this
+ *      |  OUT  | y | n |  combination of ev_type and direction)
+ *      --------+---+---+
+ *
+ * Control: DONE
+ * Int: IN PROGRESS
+ * Bulk: TODO
+ * Isoc: TODO
  */
 
 /*