Function bounce_bus_dmamap_load_buffer

freebsd/arm64/arm64/busdma_bounce.c:891–1002

* Utility function to load a linear buffer. segp contains * the starting segment on entrace, and the ending segment on exit. */

 * the starting segment on entrace, and the ending segment on exit.
 */
static int
bounce_bus_dmamap_load_buffer(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
    bus_size_t buflen, pmap_t pmap, int flags, bus_dma_segment_t *segs,
    int *segp)
{
	struct sync_list *sl;
	bus_size_t sgsize;
	bus_addr_t curaddr, sl_pend;
	vm_offset_t kvaddr, vaddr, sl_vend;
	int error;

	KASSERT((map->flags & DMAMAP_FROM_DMAMEM) != 0 ||
	    dmat->common.alignment <= PAGE_SIZE,
	    ("loading user buffer with alignment bigger than PAGE_SIZE is not "
	    "supported"));

	if (segs == NULL)
		segs = dmat->segments;

	if (flags & BUS_DMA_LOAD_MBUF)
		map->flags |= DMAMAP_MBUF;

	if (might_bounce(dmat, map, (bus_addr_t)buf, buflen)) {
		_bus_dmamap_count_pages(dmat, map, pmap, buf, buflen, flags);
		if (map->pagesneeded != 0) {
			error = _bus_dmamap_reserve_pages(dmat, map, flags);
			if (error)
				return (error);
		}
	}

	/*
	 * XXX Optimally we should parse input buffer for physically
	 * continuous segments first and then pass these segment into
	 * load loop.
	 */
	sl = map->slist + map->sync_count - 1;
	vaddr = (vm_offset_t)buf;
	sl_pend = 0;
	sl_vend = 0;

	while (buflen > 0) {
		/*
		 * Get the physical address for this segment.
		 */
		if (__predict_true(pmap == kernel_pmap)) {
			curaddr = pmap_kextract(vaddr);
			kvaddr = vaddr;
		} else {
			curaddr = pmap_extract(pmap, vaddr);
			kvaddr = 0;
		}

		/*
		 * Compute the segment size, and adjust counts.
		 */
		sgsize = MIN(buflen, dmat->common.maxsegsz);
		if ((map->flags & DMAMAP_FROM_DMAMEM) == 0)