xref: /netbsd-src/sys/rump/dev/lib/libpci/rumpdev_bus_dma.c (revision 7d871188651c65ef64e21c82f0c1a6f16c22f6f9)
1 /*	$NetBSD: rumpdev_bus_dma.c,v 1.11 2022/02/13 19:20:41 riastradh Exp $	*/
2 
3 /*-
4  * Copyright (c) 2013 Antti Kantee
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS
17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26  * POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 /*-
30  * Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
31  * All rights reserved.
32  *
33  * This code is derived from software contributed to The NetBSD Foundation
34  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
35  * NASA Ames Research Center.
36  *
37  * Redistribution and use in source and binary forms, with or without
38  * modification, are permitted provided that the following conditions
39  * are met:
40  * 1. Redistributions of source code must retain the above copyright
41  *    notice, this list of conditions and the following disclaimer.
42  * 2. Redistributions in binary form must reproduce the above copyright
43  *    notice, this list of conditions and the following disclaimer in the
44  *    documentation and/or other materials provided with the distribution.
45  *
46  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
47  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
48  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
49  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
50  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
51  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
52  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
53  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
54  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
55  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
56  * POSSIBILITY OF SUCH DAMAGE.
57  */
58 
59 /*
60  * bus_dma(9) implementation which runs on top of rump kernel hypercalls.
61  * It's essentially the same as the PowerPC implementation its based on,
62  * except with some indirection and PowerPC MD features removed.
63  * This should/could be expected to run on x86, other archs may need
64  * some cache flushing hooks.
65  *
66  * From sys/arch/powerpc/powerpc/bus_dma.c:
67  *	NetBSD: bus_dma.c,v 1.46 2012/02/01 09:54:03 matt Exp
68  */
69 
70 #include <sys/cdefs.h>
71 __KERNEL_RCSID(0, "$NetBSD: rumpdev_bus_dma.c,v 1.11 2022/02/13 19:20:41 riastradh Exp $");
72 
73 #include <sys/param.h>
74 #include <sys/systm.h>
75 #include <sys/kernel.h>
76 #include <sys/device.h>
77 #include <sys/kmem.h>
78 #include <sys/proc.h>
79 #include <sys/mbuf.h>
80 #include <sys/bus.h>
81 #include <sys/intr.h>
82 
83 #include "pci_user.h"
84 
85 int	_bus_dmamap_load_buffer (bus_dma_tag_t, bus_dmamap_t, void *,
86 	    bus_size_t, struct vmspace *, int, paddr_t *, int *, int);
87 
88 /*
89  * Common function for DMA map creation.  May be called by bus-specific
90  * DMA map creation functions.
91  */
92 int
bus_dmamap_create(bus_dma_tag_t t,bus_size_t size,int nsegments,bus_size_t maxsegsz,bus_size_t boundary,int flags,bus_dmamap_t * dmamp)93 bus_dmamap_create(bus_dma_tag_t t, bus_size_t size, int nsegments,
94 	bus_size_t maxsegsz, bus_size_t boundary, int flags,
95 	bus_dmamap_t *dmamp)
96 {
97 	bus_dmamap_t map;
98 	void *mapstore;
99 	size_t mapsize;
100 
101 	/*
102 	 * Allocate and initialize the DMA map.  The end of the map
103 	 * is a variable-sized array of segments, so we allocate enough
104 	 * room for them in one shot.
105 	 *
106 	 * Note we don't preserve the WAITOK or NOWAIT flags.  Preservation
107 	 * of ALLOCNOW notifies others that we've reserved these resources,
108 	 * and they are not to be freed.
109 	 *
110 	 * The bus_dmamap_t includes one bus_dma_segment_t, hence
111 	 * the (nsegments - 1).
112 	 */
113 	mapsize = sizeof(*map) + sizeof(bus_dma_segment_t [nsegments - 1]);
114 	if ((mapstore = kmem_intr_alloc(mapsize,
115 	    (flags & BUS_DMA_NOWAIT) ? KM_NOSLEEP : KM_SLEEP)) == NULL)
116 		return (ENOMEM);
117 
118 	memset(mapstore, 0, mapsize);
119 	map = (void *)mapstore;
120 	map->_dm_size = size;
121 	map->_dm_segcnt = nsegments;
122 	map->_dm_maxmaxsegsz = maxsegsz;
123 	map->_dm_boundary = boundary;
124 	map->_dm_bounce_thresh = 0;
125 	map->_dm_flags = flags & ~(BUS_DMA_WAITOK|BUS_DMA_NOWAIT);
126 	map->dm_maxsegsz = maxsegsz;
127 	map->dm_mapsize = 0;		/* no valid mappings */
128 	map->dm_nsegs = 0;
129 
130 	*dmamp = map;
131 	return (0);
132 }
133 
134 /*
135  * Common function for DMA map destruction.  May be called by bus-specific
136  * DMA map destruction functions.
137  */
138 void
bus_dmamap_destroy(bus_dma_tag_t t,bus_dmamap_t map)139 bus_dmamap_destroy(bus_dma_tag_t t, bus_dmamap_t map)
140 {
141 
142 	size_t mapsize = sizeof(*map)
143 	    + sizeof(bus_dma_segment_t [map->_dm_segcnt - 1]);
144 	kmem_intr_free(map, mapsize);
145 }
146 
147 /*
148  * Utility function to load a linear buffer.  lastaddrp holds state
149  * between invocations (for multiple-buffer loads).  segp contains
150  * the starting segment on entrance, and the ending segment on exit.
151  * first indicates if this is the first invocation of this function.
152  */
153 int
_bus_dmamap_load_buffer(bus_dma_tag_t t,bus_dmamap_t map,void * buf,bus_size_t buflen,struct vmspace * vm,int flags,paddr_t * lastaddrp,int * segp,int first)154 _bus_dmamap_load_buffer(bus_dma_tag_t t, bus_dmamap_t map,
155 	void *buf, bus_size_t buflen, struct vmspace *vm, int flags,
156 	paddr_t *lastaddrp, int *segp, int first)
157 {
158 	bus_size_t sgsize;
159 	bus_addr_t curaddr, lastaddr, baddr, bmask;
160 	vaddr_t vaddr = (vaddr_t)buf;
161 	int seg;
162 
163 //	printf("%s(%p,%p,%p,%u,%p,%#x,%p,%p,%u)\n", __func__,
164 //	    t, map, buf, buflen, vm, flags, lastaddrp, segp, first);
165 
166 	lastaddr = *lastaddrp;
167 	bmask = ~(map->_dm_boundary - 1);
168 
169 	for (seg = *segp; buflen > 0 ; ) {
170 		/*
171 		 * Get the physical address for this segment.
172 		 */
173 		if (!VMSPACE_IS_KERNEL_P(vm))
174 			(void) pmap_extract(vm_map_pmap(&vm->vm_map),
175 			    vaddr, (void *)&curaddr);
176 		else
177 			curaddr = vtophys(vaddr);
178 
179 		/*
180 		 * If we're beyond the bounce threshold, notify
181 		 * the caller.
182 		 */
183 		if (map->_dm_bounce_thresh != 0 &&
184 		    curaddr >= map->_dm_bounce_thresh)
185 			return (EINVAL);
186 
187 		/*
188 		 * Compute the segment size, and adjust counts.
189 		 */
190 		sgsize = PAGE_SIZE - ((u_long)vaddr & PGOFSET);
191 		if (buflen < sgsize)
192 			sgsize = buflen;
193 		sgsize = MIN(sgsize, map->dm_maxsegsz);
194 
195 		/*
196 		 * Make sure we don't cross any boundaries.
197 		 */
198 		if (map->_dm_boundary > 0) {
199 			baddr = (curaddr + map->_dm_boundary) & bmask;
200 			if (sgsize > (baddr - curaddr))
201 				sgsize = (baddr - curaddr);
202 		}
203 
204 		/*
205 		 * Insert chunk into a segment, coalescing with
206 		 * the previous segment if possible.
207 		 */
208 		if (first) {
209 			map->dm_segs[seg].ds_addr
210 			    = rumpcomp_pci_virt_to_mach((void *)curaddr);
211 			map->dm_segs[seg].ds_len = sgsize;
212 			first = 0;
213 		} else {
214 			if (curaddr == lastaddr &&
215 			    (map->dm_segs[seg].ds_len + sgsize) <=
216 			     map->dm_maxsegsz &&
217 			    (map->_dm_boundary == 0 ||
218 			     (map->dm_segs[seg].ds_addr & bmask) ==
219 			     (rumpcomp_pci_virt_to_mach((void*)curaddr)&bmask)))
220 				map->dm_segs[seg].ds_len += sgsize;
221 			else {
222 				if (++seg >= map->_dm_segcnt)
223 					break;
224 				map->dm_segs[seg].ds_addr =
225 				    rumpcomp_pci_virt_to_mach((void *)curaddr);
226 				map->dm_segs[seg].ds_len = sgsize;
227 			}
228 		}
229 
230 		lastaddr = curaddr + sgsize;
231 		vaddr += sgsize;
232 		buflen -= sgsize;
233 	}
234 
235 	*segp = seg;
236 	*lastaddrp = lastaddr;
237 
238 	/*
239 	 * Did we fit?
240 	 */
241 	if (buflen != 0)
242 		return (EFBIG);		/* XXX better return value here? */
243 
244 	return (0);
245 }
246 
247 /*
248  * Common function for loading a DMA map with a linear buffer.  May
249  * be called by bus-specific DMA map load functions.
250  */
251 int
bus_dmamap_load(bus_dma_tag_t t,bus_dmamap_t map,void * buf,bus_size_t buflen,struct proc * p,int flags)252 bus_dmamap_load(bus_dma_tag_t t, bus_dmamap_t map,
253 	void *buf, bus_size_t buflen, struct proc *p, int flags)
254 {
255 	paddr_t lastaddr = 0;
256 	int seg, error;
257 	struct vmspace *vm;
258 
259 	/*
260 	 * Make sure that on error condition we return "no valid mappings".
261 	 */
262 	map->dm_mapsize = 0;
263 	map->dm_nsegs = 0;
264 	KASSERT(map->dm_maxsegsz <= map->_dm_maxmaxsegsz);
265 
266 	if (buflen > map->_dm_size)
267 		return (EINVAL);
268 
269 	if (p != NULL) {
270 		vm = p->p_vmspace;
271 	} else {
272 		vm = vmspace_kernel();
273 	}
274 
275 	seg = 0;
276 	error = _bus_dmamap_load_buffer(t, map, buf, buflen, vm, flags,
277 		&lastaddr, &seg, 1);
278 	if (error == 0) {
279 		map->dm_mapsize = buflen;
280 		map->dm_nsegs = seg + 1;
281 	}
282 	return (error);
283 }
284 
285 /*
286  * Like _bus_dmamap_load(), but for mbufs.
287  */
288 int
bus_dmamap_load_mbuf(bus_dma_tag_t t,bus_dmamap_t map,struct mbuf * m0,int flags)289 bus_dmamap_load_mbuf(bus_dma_tag_t t, bus_dmamap_t map,
290 	struct mbuf *m0, int flags)
291 {
292 	paddr_t lastaddr = 0;
293 	int seg, error, first;
294 	struct mbuf *m;
295 
296 	/*
297 	 * Make sure that on error condition we return "no valid mappings."
298 	 */
299 	map->dm_mapsize = 0;
300 	map->dm_nsegs = 0;
301 	KASSERT(map->dm_maxsegsz <= map->_dm_maxmaxsegsz);
302 
303 #ifdef DIAGNOSTIC
304 	if ((m0->m_flags & M_PKTHDR) == 0)
305 		panic("_bus_dmamap_load_mbuf: no packet header");
306 #endif
307 
308 	if (m0->m_pkthdr.len > map->_dm_size)
309 		return (EINVAL);
310 
311 	first = 1;
312 	seg = 0;
313 	error = 0;
314 	for (m = m0; m != NULL && error == 0; m = m->m_next, first = 0) {
315 		if (m->m_len == 0)
316 			continue;
317 #ifdef POOL_VTOPHYS
318 		/* XXX Could be better about coalescing. */
319 		/* XXX Doesn't check boundaries. */
320 		switch (m->m_flags & (M_EXT|M_EXT_CLUSTER)) {
321 		case M_EXT|M_EXT_CLUSTER:
322 			/* XXX KDASSERT */
323 			KASSERT(m->m_ext.ext_paddr != M_PADDR_INVALID);
324 			lastaddr = m->m_ext.ext_paddr +
325 			    (m->m_data - m->m_ext.ext_buf);
326  have_addr:
327 			if (first == 0 && ++seg >= map->_dm_segcnt) {
328 				error = EFBIG;
329 				continue;
330 			}
331 			map->dm_segs[seg].ds_addr =
332 			    rumpcomp_pci_virt_to_mach((void *)lastaddr);
333 			map->dm_segs[seg].ds_len = m->m_len;
334 			lastaddr += m->m_len;
335 			continue;
336 
337 		case 0:
338 			lastaddr = m->m_paddr + M_BUFOFFSET(m) +
339 			    (m->m_data - M_BUFADDR(m));
340 			goto have_addr;
341 
342 		default:
343 			break;
344 		}
345 #endif
346 		error = _bus_dmamap_load_buffer(t, map, m->m_data,
347 		    m->m_len, vmspace_kernel(), flags, &lastaddr, &seg, first);
348 	}
349 	if (error == 0) {
350 		map->dm_mapsize = m0->m_pkthdr.len;
351 		map->dm_nsegs = seg + 1;
352 	}
353 	return (error);
354 }
355 
356 /*
357  * Like _bus_dmamap_load(), but for uios.
358  */
359 int
bus_dmamap_load_uio(bus_dma_tag_t t,bus_dmamap_t map,struct uio * uio,int flags)360 bus_dmamap_load_uio(bus_dma_tag_t t, bus_dmamap_t map,
361 	struct uio *uio, int flags)
362 {
363 	paddr_t lastaddr = 0;
364 	int seg, i, error, first;
365 	bus_size_t minlen, resid;
366 	struct iovec *iov;
367 	void *addr;
368 
369 	/*
370 	 * Make sure that on error condition we return "no valid mappings."
371 	 */
372 	map->dm_mapsize = 0;
373 	map->dm_nsegs = 0;
374 	KASSERT(map->dm_maxsegsz <= map->_dm_maxmaxsegsz);
375 
376 	resid = uio->uio_resid;
377 	iov = uio->uio_iov;
378 
379 	first = 1;
380 	seg = 0;
381 	error = 0;
382 	for (i = 0; i < uio->uio_iovcnt && resid != 0 && error == 0; i++) {
383 		/*
384 		 * Now at the first iovec to load.  Load each iovec
385 		 * until we have exhausted the residual count.
386 		 */
387 		minlen = resid < iov[i].iov_len ? resid : iov[i].iov_len;
388 		addr = (void *)iov[i].iov_base;
389 
390 		error = _bus_dmamap_load_buffer(t, map, addr, minlen,
391 		    uio->uio_vmspace, flags, &lastaddr, &seg, first);
392 		first = 0;
393 
394 		resid -= minlen;
395 	}
396 	if (error == 0) {
397 		map->dm_mapsize = uio->uio_resid;
398 		map->dm_nsegs = seg + 1;
399 	}
400 	return (error);
401 }
402 
403 /*
404  * Like _bus_dmamap_load(), but for raw memory allocated with
405  * bus_dmamem_alloc().
406  */
407 int
bus_dmamap_load_raw(bus_dma_tag_t t,bus_dmamap_t map,bus_dma_segment_t * segs,int nsegs,bus_size_t size,int flags)408 bus_dmamap_load_raw(bus_dma_tag_t t, bus_dmamap_t map,
409 	bus_dma_segment_t *segs, int nsegs, bus_size_t size, int flags)
410 {
411 
412 	panic("_bus_dmamap_load_raw: not implemented");
413 }
414 
415 /*
416  * Common function for unloading a DMA map.  May be called by
417  * chipset-specific DMA map unload functions.
418  */
419 void
bus_dmamap_unload(bus_dma_tag_t t,bus_dmamap_t map)420 bus_dmamap_unload(bus_dma_tag_t t, bus_dmamap_t map)
421 {
422 
423 	/*
424 	 * No resources to free; just mark the mappings as
425 	 * invalid.
426 	 */
427 	map->dm_maxsegsz = map->_dm_maxmaxsegsz;
428 	map->dm_mapsize = 0;
429 	map->dm_nsegs = 0;
430 }
431 
432 void
bus_dmamap_sync(bus_dma_tag_t t,bus_dmamap_t map,bus_addr_t offset,bus_size_t len,int ops)433 bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map,
434 	bus_addr_t offset, bus_size_t len, int ops)
435 {
436 
437 	/* XXX: this might need some MD tweaks */
438 	membar_sync();
439 }
440 
441 /*
442  * Common function for freeing DMA-safe memory.  May be called by
443  * bus-specific DMA memory free functions.
444  */
445 void
bus_dmamem_free(bus_dma_tag_t t,bus_dma_segment_t * segs,int nsegs)446 bus_dmamem_free(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs)
447 {
448 #ifdef RUMPCOMP_USERFEATURE_PCI_DMAFREE
449 	vaddr_t vacookie = segs[0]._ds_vacookie;
450 	bus_size_t sizecookie = segs[0]._ds_sizecookie;
451 
452 	rumpcomp_pci_dmafree(vacookie, sizecookie);
453 #else
454 	panic("bus_dmamem_free not implemented");
455 #endif
456 }
457 
458 /*
459  * Don't have hypercall for mapping scatter-gather memory.
460  * So just simply fail if there's more than one segment to map
461  */
462 int
bus_dmamem_map(bus_dma_tag_t t,bus_dma_segment_t * segs,int nsegs,size_t size,void ** kvap,int flags)463 bus_dmamem_map(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs,
464 	size_t size, void **kvap, int flags)
465 {
466 	struct rumpcomp_pci_dmaseg *dss;
467 	size_t allocsize = nsegs * sizeof(*dss);
468 	int rv, i;
469 
470 	/*
471 	 * Though rumpcomp_pci_dmaseg "accidentally" matches the
472 	 * bus_dma segment descriptor (at least for now), act
473 	 * proper and actually translate it.
474 	 */
475 	dss = kmem_alloc(allocsize, KM_SLEEP);
476 	for (i = 0; i < nsegs; i++) {
477 		dss[i].ds_pa = segs[i].ds_addr;
478 		dss[i].ds_len = segs[i].ds_len;
479 		dss[i].ds_vacookie = segs[i]._ds_vacookie;
480 	}
481 	rv = rumpcomp_pci_dmamem_map(dss, nsegs, size, kvap);
482 	kmem_free(dss, allocsize);
483 
484 	return rv;
485 }
486 
487 /*
488  * Common function for unmapping DMA-safe memory.  May be called by
489  * bus-specific DMA memory unmapping functions.
490  */
491 void
bus_dmamem_unmap(bus_dma_tag_t t,void * kva,size_t size)492 bus_dmamem_unmap(bus_dma_tag_t t, void *kva, size_t size)
493 {
494 
495 	/* nothing to do as long as bus_dmamem_map() is what it is */
496 }
497 
498 paddr_t
bus_dmamem_mmap(bus_dma_tag_t t,bus_dma_segment_t * segs,int nsegs,off_t off,int prot,int flags)499 bus_dmamem_mmap(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs,
500 	off_t off, int prot, int flags)
501 {
502 
503 	panic("bus_dmamem_mmap not supported");
504 }
505 
506 /*
507  * Allocate physical memory from the given physical address range.
508  * Called by DMA-safe memory allocation methods.
509  */
510 int
bus_dmamem_alloc(bus_dma_tag_t t,bus_size_t size,bus_size_t alignment,bus_size_t boundary,bus_dma_segment_t * segs,int nsegs,int * rsegs,int flags)511 bus_dmamem_alloc(bus_dma_tag_t t, bus_size_t size, bus_size_t alignment,
512 	bus_size_t boundary, bus_dma_segment_t *segs, int nsegs, int *rsegs,
513 	int flags)
514 {
515 	paddr_t curaddr, lastaddr, pa;
516 	vaddr_t vacookie;
517 	size_t sizecookie;
518 	int curseg, error;
519 
520 	/* Always round the size. */
521 	size = round_page(size);
522 
523 	sizecookie = size;
524 
525 	/*
526 	 * Allocate pages from the VM system.
527 	 */
528 #if 0
529 	error = uvm_pglistalloc(size, low, high, alignment, boundary,
530 	    &mlist, nsegs, (flags & BUS_DMA_NOWAIT) == 0);
531 #else
532 	/* XXX: ignores boundary, nsegs, etc. */
533 	//printf("dma allocation %lx %lx %d\n", alignment, boundary, nsegs);
534 	error = rumpcomp_pci_dmalloc(size, alignment, &pa, &vacookie);
535 #endif
536 	if (error)
537 		return (error);
538 
539 	/*
540 	 * Compute the location, size, and number of segments actually
541 	 * returned by the VM code.
542 	 */
543 	curseg = 0;
544 	lastaddr = segs[curseg].ds_addr = pa;
545 	segs[curseg].ds_len = PAGE_SIZE;
546 	segs[curseg]._ds_vacookie = vacookie;
547 	segs[curseg]._ds_sizecookie = sizecookie;
548 	size -= PAGE_SIZE;
549 	pa += PAGE_SIZE;
550 	vacookie += PAGE_SIZE;
551 
552 	for (; size;
553 	    pa += PAGE_SIZE, vacookie += PAGE_SIZE, size -= PAGE_SIZE) {
554 		curaddr = pa;
555 		if (curaddr == (lastaddr + PAGE_SIZE) &&
556 		    (lastaddr & boundary) == (curaddr & boundary)) {
557 			segs[curseg].ds_len += PAGE_SIZE;
558 		} else {
559 			curseg++;
560 			if (curseg >= nsegs)
561 				return EFBIG;
562 			segs[curseg].ds_addr = curaddr;
563 			segs[curseg].ds_len = PAGE_SIZE;
564 			segs[curseg]._ds_vacookie = vacookie;
565 			segs[curseg]._ds_sizecookie = sizecookie;
566 		}
567 		lastaddr = curaddr;
568 	}
569 	*rsegs = curseg + 1;
570 
571 	return (0);
572 }
573