IWM_MAX_SCATTER
nsegments = IWM_MAX_SCATTER - 2;
bus_dma_segment_t *seg, segs[IWM_MAX_SCATTER];
segs, IWM_MAX_SCATTER - 2,
m1 = m_collapse(m, M_WAITOK, IWM_MAX_SCATTER - 2);
&m, segs, IWM_MAX_SCATTER - 2, &nsegs, BUS_DMA_NOWAIT);