vmbus_br_idxinc
return vmbus_br_idxinc(windex, cplen, br_dsize);
next_windex = vmbus_br_idxinc(old_windex, total, ring_size);
return vmbus_br_idxinc(rindex, cplen, br_dsize);
rindex = vmbus_br_idxinc(rbr->vbr->rindex, skip, br_dsize);
rindex = vmbus_br_idxinc(rindex, sizeof(uint64_t), br_dsize);