+ * Populate buffer ptr and size, DMA buffer or SG list for the dto urb.
+ */
+static int __wa_populate_dto_urb(struct wa_xfer *xfer,
+ struct wa_seg *seg, size_t buf_itr_offset, size_t buf_itr_size)
+{
+ int result = 0;
+
+ if (xfer->is_dma) {
+ seg->dto_urb->transfer_dma =
+ xfer->urb->transfer_dma + buf_itr_offset;
+ seg->dto_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+ seg->dto_urb->sg = NULL;
+ seg->dto_urb->num_sgs = 0;
+ } else {
+ /* do buffer or SG processing. */
+ seg->dto_urb->transfer_flags &=
+ ~URB_NO_TRANSFER_DMA_MAP;
+ /* this should always be 0 before a resubmit. */
+ seg->dto_urb->num_mapped_sgs = 0;
+
+ if (xfer->urb->transfer_buffer) {
+ seg->dto_urb->transfer_buffer =
+ xfer->urb->transfer_buffer +
+ buf_itr_offset;
+ seg->dto_urb->sg = NULL;
+ seg->dto_urb->num_sgs = 0;
+ } else {
+ seg->dto_urb->transfer_buffer = NULL;
+
+ /*
+ * allocate an SG list to store seg_size bytes
+ * and copy the subset of the xfer->urb->sg that
+ * matches the buffer subset we are about to
+ * read.
+ */
+ seg->dto_urb->sg = wa_xfer_create_subset_sg(
+ xfer->urb->sg,
+ buf_itr_offset, buf_itr_size,
+ &(seg->dto_urb->num_sgs));
+ if (!(seg->dto_urb->sg))
+ result = -ENOMEM;
+ }
+ }
+ seg->dto_urb->transfer_buffer_length = buf_itr_size;
+
+ return result;
+}
+
+/*