Function _bus_dmamap_load_buffer

freebsd/mips/mips/busdma_machdep.c:978–1058

* Utility function to load a linear buffer. segp contains * the starting segment on entrance, and the ending segment on exit. * first indicates if this is the first invocation of this function. */

 * first indicates if this is the first invocation of this function.
 */
int
_bus_dmamap_load_buffer(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
    bus_size_t buflen, struct pmap *pmap, int flags, bus_dma_segment_t *segs,
    int *segp)
{
	bus_size_t sgsize;
	bus_addr_t curaddr;
	struct sync_list *sl;
	vm_offset_t vaddr = (vm_offset_t)buf;
	int error = 0;

	if (segs == NULL)
		segs = dmat->segments;
	if ((flags & BUS_DMA_LOAD_MBUF) != 0)
		map->flags |= DMAMAP_CACHE_ALIGNED;

	if ((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) {
		_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);
		}
	}
	CTR3(KTR_BUSDMA, "lowaddr= %d boundary= %d, "
	    "alignment= %d", dmat->lowaddr, dmat->boundary, dmat->alignment);

	while (buflen > 0) {
		/*
		 * Get the physical address for this segment.
		 *
		 * XXX Don't support checking for coherent mappings
		 * XXX in user address space.
		 */
		KASSERT(kernel_pmap == pmap, ("pmap is not kernel pmap"));
		curaddr = pmap_kextract(vaddr);

		/*
		 * Compute the segment size, and adjust counts.
		 */
		sgsize = PAGE_SIZE - ((u_long)curaddr & PAGE_MASK);
		if (sgsize > dmat->maxsegsz)
			sgsize = dmat->maxsegsz;
		if (buflen < sgsize)
			sgsize = buflen;

		if (((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) &&
		    map->pagesneeded != 0 && run_filter(dmat, curaddr)) {
			curaddr = add_bounce_page(dmat, map, vaddr, curaddr,
			    sgsize);
		} else {
			sl = &map->slist[map->sync_count - 1];
			if (map->sync_count == 0 ||
			    vaddr != sl->vaddr + sl->datacount) {
				if (++map->sync_count > dmat->nsegments)
					goto cleanup;
				sl++;
				sl->vaddr = vaddr;