Function bus_dmamap_create

freebsd/mips/mips/busdma_machdep.c:547–622

* Allocate a handle for mapping from kva/uva/physical * address space into bus device space. */

 * address space into bus device space.
 */
int
bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
{
	bus_dmamap_t newmap;
	int error = 0;

	if (dmat->segments == NULL) {
		dmat->segments = (bus_dma_segment_t *)malloc(
		    sizeof(bus_dma_segment_t) * dmat->nsegments, M_BUSDMA,
		    M_NOWAIT);
		if (dmat->segments == NULL) {
			CTR3(KTR_BUSDMA, "%s: tag %p error %d",
			    __func__, dmat, ENOMEM);
			return (ENOMEM);
		}
	}

	newmap = _busdma_alloc_dmamap(dmat);
	if (newmap == NULL) {
		CTR3(KTR_BUSDMA, "%s: tag %p error %d", __func__, dmat, ENOMEM);
		return (ENOMEM);
	}
	*mapp = newmap;

	/*
	 * Bouncing might be required if the driver asks for an active
	 * exclusion region, a data alignment that is stricter than 1, and/or
	 * an active address boundary.
	 */
	if (dmat->flags & BUS_DMA_COULD_BOUNCE) {
		/* Must bounce */
		struct bounce_zone *bz;
		int maxpages;

		if (dmat->bounce_zone == NULL) {
			if ((error = alloc_bounce_zone(dmat)) != 0) {
				_busdma_free_dmamap(newmap);
				*mapp = NULL;
				return (error);
			}
		}
		bz = dmat->bounce_zone;

		/* Initialize the new map */
		STAILQ_INIT(&((*mapp)->bpages));

		/*
		 * Attempt to add pages to our pool on a per-instance
		 * basis up to a sane limit.
		 */
		maxpages = MAX_BPAGES;
		if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0
		 || (bz->map_count > 0 && bz->total_bpages < maxpages)) {
			int pages;

			pages = MAX(atop(dmat->maxsize), 1);
			pages = MIN(maxpages - bz->total_bpages, pages);
			pages = MAX(pages, 1);