Linux: fix logical URB allocation

We were allocating the wrong number of URBs for transfers of size
multiples of 16k.

diff --git a/TODO b/TODO
index 955e501..289798f 100644 (file)
--- a/TODO
+++ b/TODO
@@ -5,7 +5,6 @@ review functionality missing over 0.1
 endianness of control setup, issues when resubmitting transfers
 doxygen warnings
 serialization of handle_events
-0.1 compat layer
 internal docs for OS porters
 
 1.0 API style/naming points to reconsider

diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 40a32f1..ec7907f 100644 (file)
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -598,7 +598,13 @@ static int submit_bulk_transfer(struct usbi_transfer *itransfer,
         * into smaller units to meet such restriction, then fire off all the
         * units at once. it would be simpler if we just fired one unit at a time,
         * but there is a big performance gain through doing it this way. */
-       int num_urbs = (transfer->length / MAX_BULK_BUFFER_LENGTH) + 1;
+       int num_urbs = transfer->length / MAX_BULK_BUFFER_LENGTH;
+       int last_urb_partial = 0;
+
+       if ((transfer->length % MAX_BULK_BUFFER_LENGTH) > 0) {
+               last_urb_partial = 1;
+               num_urbs++;
+       }
        usbi_dbg("need %d urbs for new transfer with length %d", num_urbs,
                transfer->length);
        alloc_size = num_urbs * sizeof(struct usbfs_urb);
@@ -618,7 +624,7 @@ static int submit_bulk_transfer(struct usbi_transfer *itransfer,
                urb->type = urb_type;
                urb->endpoint = transfer->endpoint;
                urb->buffer = transfer->buffer + (i * MAX_BULK_BUFFER_LENGTH);
-               if (i == num_urbs - 1)
+               if (i == num_urbs - 1 && last_urb_partial)
                        urb->buffer_length = transfer->length % MAX_BULK_BUFFER_LENGTH;
                else
                        urb->buffer_length = MAX_BULK_BUFFER_LENGTH;