Linux: Handle early complete of multi-URB transfer

diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 67d2a87..d0db7e2 100644 (file)
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -1415,7 +1415,7 @@ static int submit_bulk_transfer(struct usbi_transfer *itransfer,
                        }
 
                        /* if it's not the first URB that failed, the situation is a bit
-                        * tricky. we must discard all previous URBs. there are
+                        * tricky. we may need to discard all previous URBs. there are
                         * complications:
                         *  - discarding is asynchronous - discarded urbs will be reaped
                         *    later. the user must not have freed the transfer when the
@@ -1423,15 +1423,23 @@ static int submit_bulk_transfer(struct usbi_transfer *itransfer,
                         *    freed memory.
                         *  - the earlier URBs may have completed successfully and we do
                         *    not want to throw away any data.
-                        * so, in this case we discard all the previous URBs BUT we report
-                        * that the transfer was submitted successfully. then later when
-                        * the final discard completes we can report error to the user.
+                        *  - this URB failing may be no error; EREMOTEIO means that
+                        *    this transfer simply didn't need all the URBs we submitted
+                        * so, we report that the transfer was submitted successfully and
+                        * in case of error we discard all previous URBs. later when
+                        * the final reap completes we can report error to the user,
+                        * or success if an earlier URB was completed successfully.
                         */
-                       tpriv->reap_action = SUBMIT_FAILED;
+                       tpriv->reap_action = EREMOTEIO == errno ? COMPLETED_EARLY : SUBMIT_FAILED;
 
                        /* The URBs we haven't submitted yet we count as already
                         * retired. */
                        tpriv->num_retired += num_urbs - i;
+
+                       /* If we completed short then don't try to discard. */
+                       if (COMPLETED_EARLY == tpriv->reap_action)
+                               return 0;
+
                        for (j = 0; j < i; j++) {
                                int tmp = ioctl(dpriv->fd, IOCTL_USBFS_DISCARDURB, &urbs[j]);
                                if (tmp && errno != EINVAL)