Ticket #6: 0001-Add-LIBUSB_TRANSFER_ZERO_PACKET-6.patch

libusb/core.c

@@ -283 +283 @@
  * kernel where boundaries occur between logical libusb-level transfers. When
  * a short transfer (or other error) occurs, the kernel will cancel all the
  * subtransfers until the boundary without allowing those transfers to start.
+ *
+ * \section zlp Zero length packets
+ *
+ * - libusb is designed to be able to send a packet of zero-length to an
+ * endpoint simply by submitting a transfer of zero length. On Linux, this did
+ * not work with libusb versions prior to v1.0.3 and kernel versions prior to
+ * v2.6.31.
+ * - The \ref libusb_transfer_flags::LIBUSB_TRANSFER_ZERO_PACKET
+ * "LIBUSB_TRANSFER_ZERO_PACKET" flag is unsupported on Darwin.
  */
 
 /**

libusb/io.c

@@ -1206 +1206 @@
  * \returns 0 on success
  * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
  * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted.
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED if the transfer flags are not supported
+ * by the operating system.
  * \returns another LIBUSB_ERROR code on other failure
  */
 API_EXPORTED int libusb_submit_transfer(struct libusb_transfer *transfer)

libusb/libusb.h

@@ -672 +672 @@
          * If this flag is set, it is illegal to call libusb_free_transfer()
          * from your transfer callback, as this will result in a double-free
          * when this flag is acted upon. */
-        LIBUSB_TRANSFER_FREE_TRANSFER = 1<<2
+        LIBUSB_TRANSFER_FREE_TRANSFER = 1<<2,
+
+        /** Terminate transfers that are a multiple of the endpoint's maximum
+         * packet size with an extra zero-length packet. This is useful when a
+         * device protocol mandates that each logical request is terminated by
+         * an incomplete packet (i.e. the logical requests are not separated by
+         * other means).
+         *
+         * This flag only affects host-to-device transfers to bulk and interrupt
+         * endpoints. In other situations, it is ignored.
+         *
+         * This flag only affects transfers with a length that is a multiple of
+         * the endpoint's packet size. On transfers of other lengths, this flag
+         * has no effect. Therefore, if you are working with a device that needs
+         * a ZLP whenever the end of the logical request falls on a packet boundary,
+         * then it is sensible to set this flag on <em>every</em> transfer (you
+         * do not have to worry about only setting it on transfers that end on the
+         * boundary).
+         *
+         * This flag is unsupported on Darwin. On Darwin, libusb_submit_transfer()
+         * will return LIBUSB_ERROR_NOT_SUPPORTED for every transfer where this flag
+         * is set.
+         *
+         * Since v1.0.5.
+         */
+        LIBUSB_TRANSFER_ZERO_PACKET = 1 << 3
 };
 
 /** \ingroup asyncio

libusb/os/darwin_usb.c

@@ -1046 +1046 @@
 
   /* are we reading or writing? */
   is_read = transfer->endpoint & LIBUSB_ENDPOINT_IN;
+
+  if (!is_read & transfer->flags & LIBUSB_TRANSFER_ZERO_PACKET)
+    return LIBUSB_ERROR_NOT_SUPPORTED;
   
   if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface) != 0) {
     _usbi_log (TRANSFER_CTX (transfer), LOG_LEVEL_ERROR, "endpoint not found on any open interface");

libusb/os/linux_usbfs.c

@@ -1376 +1376 @@
                 if (i > 0 && supports_flag_bulk_continuation)
                         urb->flags |= USBFS_URB_BULK_CONTINUATION;
 
+                if (transfer->flags & LIBUSB_TRANSFER_ZERO_PACKET && i == num_urbs - 1)
+                        urb->flags |= USBFS_URB_ZERO_PACKET;
+
                 r = ioctl(dpriv->fd, IOCTL_USBFS_SUBMITURB, urb);
                 if (r < 0) {
                         int j;

libusb/os/linux_usbfs.h

@@ -64 +64 @@
 #define USBFS_URB_ISO_ASAP                      0x02
 #define USBFS_URB_BULK_CONTINUATION     0x04
 #define USBFS_URB_QUEUE_BULK            0x10
+#define USBFS_URB_ZERO_PACKET           0x40
 
 enum usbfs_urb_type {
         USBFS_URB_TYPE_ISO = 0,