+ if (subs->hwptr_done >= runtime->buffer_size * stride)
+ subs->hwptr_done -= runtime->buffer_size * stride;
+}
+
+static void copy_to_urb(struct snd_usb_substream *subs, struct urb *urb,
+ int offset, int stride, unsigned int bytes)
+{
+ struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
+
+ if (subs->hwptr_done + bytes > runtime->buffer_size * stride) {
+ /* err, the transferred area goes over buffer boundary. */
+ unsigned int bytes1 =
+ runtime->buffer_size * stride - subs->hwptr_done;
+ memcpy(urb->transfer_buffer + offset,
+ runtime->dma_area + subs->hwptr_done, bytes1);
+ memcpy(urb->transfer_buffer + offset + bytes1,
+ runtime->dma_area, bytes - bytes1);
+ } else {
+ memcpy(urb->transfer_buffer + offset,
+ runtime->dma_area + subs->hwptr_done, bytes);
+ }
+ subs->hwptr_done += bytes;
+ if (subs->hwptr_done >= runtime->buffer_size * stride)
+ subs->hwptr_done -= runtime->buffer_size * stride;
+}
+
+static unsigned int copy_to_urb_quirk(struct snd_usb_substream *subs,
+ struct urb *urb, int stride,
+ unsigned int bytes)
+{
+ __le32 packet_length;
+ int i;
+
+ /* Put __le32 length descriptor at start of each packet. */
+ for (i = 0; i < urb->number_of_packets; i++) {
+ unsigned int length = urb->iso_frame_desc[i].length;
+ unsigned int offset = urb->iso_frame_desc[i].offset;
+
+ packet_length = cpu_to_le32(length);
+ offset += i * sizeof(packet_length);
+ urb->iso_frame_desc[i].offset = offset;
+ urb->iso_frame_desc[i].length += sizeof(packet_length);
+ memcpy(urb->transfer_buffer + offset,
+ &packet_length, sizeof(packet_length));
+ copy_to_urb(subs, urb, offset + sizeof(packet_length),
+ stride, length);
+ }
+ /* Adjust transfer size accordingly. */
+ bytes += urb->number_of_packets * sizeof(packet_length);
+ return bytes;