MAX_DMA_DESC_NUM_HS_ISOC
return (frame_idx & ((MAX_DMA_DESC_NUM_HS_ISOC / 8) - 1)) * 8;
((speed == USB_SPEED_HIGH ? MAX_DMA_DESC_NUM_HS_ISOC :
((speed == USB_SPEED_HIGH ? MAX_DMA_DESC_NUM_HS_ISOC :
MAX_DMA_DESC_NUM_HS_ISOC : MAX_DMA_DESC_NUM_GENERIC;