2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2012 EMC Corp.
7 * Copyright (c) 1997, 1998 Justin T. Gibbs.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
36 #include "opt_iommu.h"
38 #include <sys/param.h>
40 #include <sys/systm.h>
43 #include <sys/callout.h>
47 #include <sys/memdesc.h>
48 #include <sys/mutex.h>
53 #include <vm/vm_page.h>
54 #include <vm/vm_map.h>
58 #include <cam/cam_ccb.h>
60 #include <opencrypto/cryptodev.h>
62 #include <machine/bus.h>
65 * Convenience function for manipulating driver locks from busdma (during
66 * busdma_swi, for example).
69 busdma_lock_mutex(void *arg, bus_dma_lock_op_t op)
73 dmtx = (struct mtx *)arg;
82 panic("Unknown operation 0x%x for busdma_lock_mutex!", op);
87 * dflt_lock should never get called. It gets put into the dma tag when
88 * lockfunc == NULL, which is only valid if the maps that are associated
89 * with the tag are meant to never be deferred.
91 * XXX Should have a way to identify which driver is responsible here.
94 _busdma_dflt_lock(void *arg, bus_dma_lock_op_t op)
97 panic("driver error: _bus_dma_dflt_lock called");
102 * Load up data starting at offset within a region specified by a
103 * list of virtual address ranges until either length or the region
107 _bus_dmamap_load_vlist(bus_dma_tag_t dmat, bus_dmamap_t map,
108 bus_dma_segment_t *list, int sglist_cnt, struct pmap *pmap, int *nsegs,
109 int flags, size_t offset, size_t length)
114 for (; sglist_cnt > 0 && length != 0; sglist_cnt--, list++) {
118 KASSERT((offset < list->ds_len),
119 ("Invalid mid-segment offset"));
120 addr = (char *)(uintptr_t)list->ds_addr + offset;
121 ds_len = list->ds_len - offset;
126 KASSERT((ds_len != 0), ("Segment length is zero"));
127 error = _bus_dmamap_load_buffer(dmat, map, addr, ds_len, pmap,
136 * Load a list of physical addresses.
139 _bus_dmamap_load_plist(bus_dma_tag_t dmat, bus_dmamap_t map,
140 bus_dma_segment_t *list, int sglist_cnt, int *nsegs, int flags)
145 for (; sglist_cnt > 0; sglist_cnt--, list++) {
146 error = _bus_dmamap_load_phys(dmat, map,
147 (vm_paddr_t)list->ds_addr, list->ds_len, flags, NULL,
156 * Load an unmapped mbuf
159 _bus_dmamap_load_mbuf_epg(bus_dma_tag_t dmat, bus_dmamap_t map,
160 struct mbuf *m, bus_dma_segment_t *segs, int *nsegs, int flags)
162 int error, i, off, len, pglen, pgoff, seglen, segoff;
169 /* Skip over any data removed from the front. */
170 off = mtod(m, vm_offset_t);
172 if (m->m_epg_hdrlen != 0) {
173 if (off >= m->m_epg_hdrlen) {
174 off -= m->m_epg_hdrlen;
176 seglen = m->m_epg_hdrlen - off;
178 seglen = min(seglen, len);
181 error = _bus_dmamap_load_buffer(dmat, map,
182 &m->m_epg_hdr[segoff], seglen, kernel_pmap,
186 pgoff = m->m_epg_1st_off;
187 for (i = 0; i < m->m_epg_npgs && error == 0 && len > 0; i++) {
188 pglen = m_epg_pagelen(m, i, pgoff);
194 seglen = pglen - off;
195 segoff = pgoff + off;
197 seglen = min(seglen, len);
199 error = _bus_dmamap_load_phys(dmat, map,
200 m->m_epg_pa[i] + segoff, seglen, flags, segs, nsegs);
203 if (len != 0 && error == 0) {
204 KASSERT((off + len) <= m->m_epg_trllen,
205 ("off + len > trail (%d + %d > %d)", off, len,
207 error = _bus_dmamap_load_buffer(dmat, map,
208 &m->m_epg_trail[off], len, kernel_pmap, flags, segs,
215 * Load a single mbuf.
218 _bus_dmamap_load_single_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map,
219 struct mbuf *m, bus_dma_segment_t *segs, int *nsegs, int flags)
224 if ((m->m_flags & M_EXTPG) != 0)
225 error = _bus_dmamap_load_mbuf_epg(dmat, map, m, segs, nsegs,
228 error = _bus_dmamap_load_buffer(dmat, map, m->m_data, m->m_len,
229 kernel_pmap, flags | BUS_DMA_LOAD_MBUF, segs, nsegs);
230 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
231 __func__, dmat, flags, error, *nsegs);
236 * Load an mbuf chain.
239 _bus_dmamap_load_mbuf_sg(bus_dma_tag_t dmat, bus_dmamap_t map,
240 struct mbuf *m0, bus_dma_segment_t *segs, int *nsegs, int flags)
246 for (m = m0; m != NULL && error == 0; m = m->m_next) {
248 if ((m->m_flags & M_EXTPG) != 0)
249 error = _bus_dmamap_load_mbuf_epg(dmat,
250 map, m, segs, nsegs, flags);
252 error = _bus_dmamap_load_buffer(dmat, map,
253 m->m_data, m->m_len, kernel_pmap,
254 flags | BUS_DMA_LOAD_MBUF, segs, nsegs);
257 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
258 __func__, dmat, flags, error, *nsegs);
263 * Load from block io.
266 _bus_dmamap_load_bio(bus_dma_tag_t dmat, bus_dmamap_t map, struct bio *bio,
267 int *nsegs, int flags)
270 if ((bio->bio_flags & BIO_VLIST) != 0) {
271 bus_dma_segment_t *segs = (bus_dma_segment_t *)bio->bio_data;
272 return (_bus_dmamap_load_vlist(dmat, map, segs, bio->bio_ma_n,
273 kernel_pmap, nsegs, flags, bio->bio_ma_offset,
277 if ((bio->bio_flags & BIO_UNMAPPED) != 0)
278 return (_bus_dmamap_load_ma(dmat, map, bio->bio_ma,
279 bio->bio_bcount, bio->bio_ma_offset, flags, NULL, nsegs));
281 return (_bus_dmamap_load_buffer(dmat, map, bio->bio_data,
282 bio->bio_bcount, kernel_pmap, flags, NULL, nsegs));
286 bus_dmamap_load_ma_triv(bus_dma_tag_t dmat, bus_dmamap_t map,
287 struct vm_page **ma, bus_size_t tlen, int ma_offs, int flags,
288 bus_dma_segment_t *segs, int *segp)
295 for (i = 0; tlen > 0; i++, tlen -= len) {
296 len = min(PAGE_SIZE - ma_offs, tlen);
297 paddr = VM_PAGE_TO_PHYS(ma[i]) + ma_offs;
298 error = _bus_dmamap_load_phys(dmat, map, paddr, len,
308 * Load a cam control block.
311 _bus_dmamap_load_ccb(bus_dma_tag_t dmat, bus_dmamap_t map, union ccb *ccb,
312 int *nsegs, int flags)
314 struct ccb_hdr *ccb_h;
322 switch (ccb_h->func_code) {
324 struct ccb_scsiio *csio;
327 data_ptr = csio->data_ptr;
328 dxfer_len = csio->dxfer_len;
329 sglist_cnt = csio->sglist_cnt;
332 case XPT_CONT_TARGET_IO: {
333 struct ccb_scsiio *ctio;
336 data_ptr = ctio->data_ptr;
337 dxfer_len = ctio->dxfer_len;
338 sglist_cnt = ctio->sglist_cnt;
342 struct ccb_ataio *ataio;
345 data_ptr = ataio->data_ptr;
346 dxfer_len = ataio->dxfer_len;
351 case XPT_NVME_ADMIN: {
352 struct ccb_nvmeio *nvmeio;
354 nvmeio = &ccb->nvmeio;
355 data_ptr = nvmeio->data_ptr;
356 dxfer_len = nvmeio->dxfer_len;
357 sglist_cnt = nvmeio->sglist_cnt;
361 panic("_bus_dmamap_load_ccb: Unsupported func code %d",
365 switch ((ccb_h->flags & CAM_DATA_MASK)) {
367 error = _bus_dmamap_load_buffer(dmat, map, data_ptr, dxfer_len,
368 kernel_pmap, flags, NULL, nsegs);
371 error = _bus_dmamap_load_phys(dmat, map,
372 (vm_paddr_t)(uintptr_t)data_ptr, dxfer_len, flags, NULL,
376 error = _bus_dmamap_load_vlist(dmat, map,
377 (bus_dma_segment_t *)data_ptr, sglist_cnt, kernel_pmap,
378 nsegs, flags, 0, dxfer_len);
380 case CAM_DATA_SG_PADDR:
381 error = _bus_dmamap_load_plist(dmat, map,
382 (bus_dma_segment_t *)data_ptr, sglist_cnt, nsegs, flags);
385 error = _bus_dmamap_load_bio(dmat, map, (struct bio *)data_ptr,
389 panic("_bus_dmamap_load_ccb: flags 0x%X unimplemented",
399 _bus_dmamap_load_uio(bus_dma_tag_t dmat, bus_dmamap_t map, struct uio *uio,
400 int *nsegs, int flags)
409 if (uio->uio_segflg == UIO_USERSPACE) {
410 KASSERT(uio->uio_td != NULL,
411 ("bus_dmamap_load_uio: USERSPACE but no proc"));
412 pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace);
415 resid = uio->uio_resid;
419 for (i = 0; i < uio->uio_iovcnt && resid != 0 && !error; i++) {
421 * Now at the first iovec to load. Load each iovec
422 * until we have exhausted the residual count.
425 addr = (caddr_t) iov[i].iov_base;
426 minlen = resid < iov[i].iov_len ? resid : iov[i].iov_len;
428 error = _bus_dmamap_load_buffer(dmat, map, addr,
429 minlen, pmap, flags, NULL, nsegs);
438 * Map the buffer buf into bus space using the dmamap map.
441 bus_dmamap_load(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
442 bus_size_t buflen, bus_dmamap_callback_t *callback,
443 void *callback_arg, int flags)
445 bus_dma_segment_t *segs;
451 mem = memdesc_vaddr(buf, buflen);
452 _bus_dmamap_load_kmsan(dmat, map, &mem);
455 if ((flags & BUS_DMA_NOWAIT) == 0) {
456 mem = memdesc_vaddr(buf, buflen);
457 _bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
461 error = _bus_dmamap_load_buffer(dmat, map, buf, buflen, kernel_pmap,
462 flags, NULL, &nsegs);
465 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
466 __func__, dmat, flags, error, nsegs);
468 if (error == EINPROGRESS)
471 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
473 (*callback)(callback_arg, segs, 0, error);
475 (*callback)(callback_arg, segs, nsegs, 0);
478 * Return ENOMEM to the caller so that it can pass it up the stack.
479 * This error only happens when NOWAIT is set, so deferral is disabled.
488 bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m0,
489 bus_dmamap_callback2_t *callback, void *callback_arg, int flags)
491 bus_dma_segment_t *segs;
497 struct memdesc mem = memdesc_mbuf(m0);
498 _bus_dmamap_load_kmsan(dmat, map, &mem);
501 flags |= BUS_DMA_NOWAIT;
503 error = _bus_dmamap_load_mbuf_sg(dmat, map, m0, NULL, &nsegs, flags);
506 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
508 (*callback)(callback_arg, segs, 0, 0, error);
510 (*callback)(callback_arg, segs, nsegs, m0->m_pkthdr.len, error);
512 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
513 __func__, dmat, flags, error, nsegs);
518 bus_dmamap_load_mbuf_sg(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m0,
519 bus_dma_segment_t *segs, int *nsegs, int flags)
524 struct memdesc mem = memdesc_mbuf(m0);
525 _bus_dmamap_load_kmsan(dmat, map, &mem);
528 flags |= BUS_DMA_NOWAIT;
530 error = _bus_dmamap_load_mbuf_sg(dmat, map, m0, segs, nsegs, flags);
532 _bus_dmamap_complete(dmat, map, segs, *nsegs, error);
537 bus_dmamap_load_uio(bus_dma_tag_t dmat, bus_dmamap_t map, struct uio *uio,
538 bus_dmamap_callback2_t *callback, void *callback_arg, int flags)
540 bus_dma_segment_t *segs;
544 struct memdesc mem = memdesc_uio(uio);
545 _bus_dmamap_load_kmsan(dmat, map, &mem);
548 flags |= BUS_DMA_NOWAIT;
550 error = _bus_dmamap_load_uio(dmat, map, uio, &nsegs, flags);
553 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
555 (*callback)(callback_arg, segs, 0, 0, error);
557 (*callback)(callback_arg, segs, nsegs, uio->uio_resid, error);
559 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
560 __func__, dmat, flags, error, nsegs);
565 bus_dmamap_load_ccb(bus_dma_tag_t dmat, bus_dmamap_t map, union ccb *ccb,
566 bus_dmamap_callback_t *callback, void *callback_arg,
569 bus_dma_segment_t *segs;
570 struct ccb_hdr *ccb_h;
576 mem = memdesc_ccb(ccb);
577 _bus_dmamap_load_kmsan(dmat, map, &mem);
581 if ((ccb_h->flags & CAM_DIR_MASK) == CAM_DIR_NONE) {
582 callback(callback_arg, NULL, 0, 0);
585 if ((flags & BUS_DMA_NOWAIT) == 0) {
586 mem = memdesc_ccb(ccb);
587 _bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
590 error = _bus_dmamap_load_ccb(dmat, map, ccb, &nsegs, flags);
593 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
594 __func__, dmat, flags, error, nsegs);
596 if (error == EINPROGRESS)
599 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
601 (*callback)(callback_arg, segs, 0, error);
603 (*callback)(callback_arg, segs, nsegs, error);
605 * Return ENOMEM to the caller so that it can pass it up the stack.
606 * This error only happens when NOWAIT is set, so deferral is disabled.
615 bus_dmamap_load_bio(bus_dma_tag_t dmat, bus_dmamap_t map, struct bio *bio,
616 bus_dmamap_callback_t *callback, void *callback_arg,
619 bus_dma_segment_t *segs;
625 mem = memdesc_bio(bio);
626 _bus_dmamap_load_kmsan(dmat, map, &mem);
629 if ((flags & BUS_DMA_NOWAIT) == 0) {
630 mem = memdesc_bio(bio);
631 _bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
634 error = _bus_dmamap_load_bio(dmat, map, bio, &nsegs, flags);
637 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
638 __func__, dmat, flags, error, nsegs);
640 if (error == EINPROGRESS)
643 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
645 (*callback)(callback_arg, segs, 0, error);
647 (*callback)(callback_arg, segs, nsegs, error);
649 * Return ENOMEM to the caller so that it can pass it up the stack.
650 * This error only happens when NOWAIT is set, so deferral is disabled.
659 bus_dmamap_load_mem(bus_dma_tag_t dmat, bus_dmamap_t map,
660 struct memdesc *mem, bus_dmamap_callback_t *callback,
661 void *callback_arg, int flags)
663 bus_dma_segment_t *segs;
668 _bus_dmamap_load_kmsan(dmat, map, mem);
671 if ((flags & BUS_DMA_NOWAIT) == 0)
672 _bus_dmamap_waitok(dmat, map, mem, callback, callback_arg);
676 switch (mem->md_type) {
678 error = _bus_dmamap_load_buffer(dmat, map, mem->u.md_vaddr,
679 mem->md_opaque, kernel_pmap, flags, NULL, &nsegs);
682 error = _bus_dmamap_load_phys(dmat, map, mem->u.md_paddr,
683 mem->md_opaque, flags, NULL, &nsegs);
686 error = _bus_dmamap_load_vlist(dmat, map, mem->u.md_list,
687 mem->md_opaque, kernel_pmap, &nsegs, flags, 0, SIZE_T_MAX);
690 error = _bus_dmamap_load_plist(dmat, map, mem->u.md_list,
691 mem->md_opaque, &nsegs, flags);
694 error = _bus_dmamap_load_bio(dmat, map, mem->u.md_bio,
698 error = _bus_dmamap_load_uio(dmat, map, mem->u.md_uio,
702 error = _bus_dmamap_load_mbuf_sg(dmat, map, mem->u.md_mbuf,
703 NULL, &nsegs, flags);
706 error = _bus_dmamap_load_ccb(dmat, map, mem->u.md_ccb, &nsegs,
712 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
713 __func__, dmat, flags, error, nsegs);
715 if (error == EINPROGRESS)
718 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
720 (*callback)(callback_arg, segs, 0, error);
722 (*callback)(callback_arg, segs, nsegs, 0);
725 * Return ENOMEM to the caller so that it can pass it up the stack.
726 * This error only happens when NOWAIT is set, so deferral is disabled.
735 bus_dmamap_load_crp_buffer(bus_dma_tag_t dmat, bus_dmamap_t map,
736 struct crypto_buffer *cb, bus_dmamap_callback_t *callback,
737 void *callback_arg, int flags)
739 bus_dma_segment_t *segs;
743 flags |= BUS_DMA_NOWAIT;
746 switch (cb->cb_type) {
747 case CRYPTO_BUF_CONTIG:
748 error = _bus_dmamap_load_buffer(dmat, map, cb->cb_buf,
749 cb->cb_buf_len, kernel_pmap, flags, NULL, &nsegs);
751 case CRYPTO_BUF_MBUF:
752 error = _bus_dmamap_load_mbuf_sg(dmat, map, cb->cb_mbuf,
753 NULL, &nsegs, flags);
755 case CRYPTO_BUF_SINGLE_MBUF:
756 error = _bus_dmamap_load_single_mbuf(dmat, map, cb->cb_mbuf,
757 NULL, &nsegs, flags);
760 error = _bus_dmamap_load_uio(dmat, map, cb->cb_uio, &nsegs,
763 case CRYPTO_BUF_VMPAGE:
764 error = _bus_dmamap_load_ma(dmat, map, cb->cb_vm_page,
765 cb->cb_vm_page_len, cb->cb_vm_page_offset, flags, NULL,
773 CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
774 __func__, dmat, flags, error, nsegs);
776 if (error == EINPROGRESS)
779 segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
781 (*callback)(callback_arg, segs, 0, error);
783 (*callback)(callback_arg, segs, nsegs, 0);
786 * Return ENOMEM to the caller so that it can pass it up the stack.
787 * This error only happens when NOWAIT is set, so deferral is disabled.
796 bus_dmamap_load_crp(bus_dma_tag_t dmat, bus_dmamap_t map, struct cryptop *crp,
797 bus_dmamap_callback_t *callback, void *callback_arg, int flags)
799 return (bus_dmamap_load_crp_buffer(dmat, map, &crp->crp_buf, callback,
800 callback_arg, flags));
804 bus_dma_template_init(bus_dma_template_t *t, bus_dma_tag_t parent)
813 t->lowaddr = t->highaddr = BUS_SPACE_MAXADDR;
814 t->maxsize = t->maxsegsize = BUS_SPACE_MAXSIZE;
815 t->nsegments = BUS_SPACE_UNRESTRICTED;
817 t->lockfuncarg = NULL;
822 bus_dma_template_tag(bus_dma_template_t *t, bus_dma_tag_t *dmat)
825 if (t == NULL || dmat == NULL)
828 return (bus_dma_tag_create(t->parent, t->alignment, t->boundary,
829 t->lowaddr, t->highaddr, NULL, NULL, t->maxsize,
830 t->nsegments, t->maxsegsize, t->flags, t->lockfunc, t->lockfuncarg,
835 bus_dma_template_fill(bus_dma_template_t *t, bus_dma_param_t *kv, u_int count)
837 bus_dma_param_t *pkv;
842 case BD_PARAM_PARENT:
843 t->parent = pkv->ptr;
845 case BD_PARAM_ALIGNMENT:
846 t->alignment = pkv->num;
848 case BD_PARAM_BOUNDARY:
849 t->boundary = pkv->num;
851 case BD_PARAM_LOWADDR:
852 t->lowaddr = pkv->pa;
854 case BD_PARAM_HIGHADDR:
855 t->highaddr = pkv->pa;
857 case BD_PARAM_MAXSIZE:
858 t->maxsize = pkv->num;
860 case BD_PARAM_NSEGMENTS:
861 t->nsegments = pkv->num;
863 case BD_PARAM_MAXSEGSIZE:
864 t->maxsegsize = pkv->num;
869 case BD_PARAM_LOCKFUNC:
870 t->lockfunc = pkv->ptr;
872 case BD_PARAM_LOCKFUNCARG:
873 t->lockfuncarg = pkv->ptr;
878 case BD_PARAM_INVALID:
880 KASSERT(0, ("Invalid key %d\n", pkv->key));
888 bool bus_dma_iommu_set_buswide(device_t dev);
889 int bus_dma_iommu_load_ident(bus_dma_tag_t dmat, bus_dmamap_t map,
890 vm_paddr_t start, vm_size_t length, int flags);
893 bus_dma_iommu_set_buswide(device_t dev)
899 bus_dma_iommu_load_ident(bus_dma_tag_t dmat, bus_dmamap_t map,
900 vm_paddr_t start, vm_size_t length, int flags)