- ep->nurbs = (total_packs + urb_packs - 1) / urb_packs;
- if (ep->nurbs > MAX_URBS) {
- /* too much... */
- ep->nurbs = MAX_URBS;
- total_packs = MAX_URBS * urb_packs;
- } else if (ep->nurbs < 2) {
- /* too little - we need at least two packets
- * to ensure contiguous playback/capture
- */
- ep->nurbs = 2;
+ /* how many packets will contain an entire ALSA period? */
+ max_packs_per_period = DIV_ROUND_UP(period_bytes, minsize);
+
+ /* how many URBs will contain a period? */
+ urbs_per_period = DIV_ROUND_UP(max_packs_per_period,
+ max_packs_per_urb);
+ /* how many packets are needed in each URB? */
+ urb_packs = DIV_ROUND_UP(max_packs_per_period, urbs_per_period);
+
+ /* limit the number of frames in a single URB */
+ ep->max_urb_frames = DIV_ROUND_UP(frames_per_period,
+ urbs_per_period);
+
+ /* try to use enough URBs to contain an entire ALSA buffer */
+ max_urbs = min((unsigned) MAX_URBS,
+ MAX_QUEUE * packs_per_ms / urb_packs);
+ ep->nurbs = min(max_urbs, urbs_per_period * periods_per_buffer);