busdma(9): Add bus_dmamap_load_mbuf_segment()

See the comment in sys/bus_dma.h for detailed information
about this function.

Let bus_dmamap_load_mbuf() call this function with busdma tag's
segments and nsegments.

Inspired-by: FreeBSD's bus_dmamap_load_mbuf_sg()

diff --git a/sys/platform/pc32/i386/busdma_machdep.c b/sys/platform/pc32/i386/busdma_machdep.c
index fed5e2f..02b2d18 100644 (file)
--- a/sys/platform/pc32/i386/busdma_machdep.c
+++ b/sys/platform/pc32/i386/busdma_machdep.c
@@ -539,6 +539,8 @@ static int
 _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
                        bus_dmamap_t map,
                        void *buf, bus_size_t buflen,
+                       bus_dma_segment_t *segments,
+                       int nsegments,
                        pmap_t pmap,
                        int flags,
                        vm_paddr_t *lastpaddrp,
@@ -607,9 +609,9 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
                BZ_UNLOCK(bz);
        }
 
-       KKASSERT(*segp >= 1 && *segp <= dmat->nsegments);
+       KKASSERT(*segp >= 1 && *segp <= nsegments);
        seg = *segp;
-       sg = &dmat->segments[seg - 1];
+       sg = &segments[seg - 1];
 
        vaddr = (vm_offset_t)buf;
        nextpaddr = *lastpaddrp;
@@ -647,7 +649,7 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
                } else {
                        sg++;
                        seg++;
-                       if (seg > dmat->nsegments)
+                       if (seg > nsegments)
                                break;
                        sg->ds_addr = paddr;
                        sg->ds_len = size;
@@ -678,7 +680,7 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
                        /*
                         * Futz, split the data into a new segment.
                         */
-                       if (seg >= dmat->nsegments)
+                       if (seg >= nsegments)
                                goto fail;
                        sg[1].ds_len = sg[0].ds_len - tmpsize;
                        sg[1].ds_addr = sg[0].ds_addr + tmpsize;
@@ -734,6 +736,7 @@ bus_dmamap_load(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
        }
 
        error = _bus_dmamap_load_buffer(dmat, map, buf, buflen,
+                       dmat->segments, dmat->nsegments,
                        NULL, flags, &lastaddr, &nsegs, 1);
        if (error == EINPROGRESS)
                return error;
@@ -753,8 +756,6 @@ bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map,
 {
        int nsegs, error;
 
-       M_ASSERTPKTHDR(m0);
-
        /*
         * XXX
         * Follow old semantics.  Once all of the callers are fixed,
@@ -763,12 +764,41 @@ bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map,
        flags &= ~BUS_DMA_WAITOK;
        flags |= BUS_DMA_NOWAIT;
 
+       error = bus_dmamap_load_mbuf_segment(dmat, map, m0,
+                       dmat->segments, dmat->nsegments, &nsegs, flags);
+       if (error) {
+               /* force "no valid mappings" in callback */
+               callback(callback_arg, dmat->segments, 0, 0, error);
+       } else {
+               callback(callback_arg, dmat->segments, nsegs,
+                        m0->m_pkthdr.len, error);
+       }
+       return error;
+}
+
+int
+bus_dmamap_load_mbuf_segment(bus_dma_tag_t dmat, bus_dmamap_t map,
+                            struct mbuf *m0,
+                            bus_dma_segment_t *segs, int maxsegs,
+                            int *nsegs, int flags)
+{
+       int error;
+
+       M_ASSERTPKTHDR(m0);
+
+       KASSERT(maxsegs >= 1, ("invalid maxsegs %d\n", maxsegs));
+       KASSERT(maxsegs <= dmat->nsegments,
+               ("%d too many segments, dmat only support %d segments\n",
+                maxsegs, dmat->nsegments));
+       KASSERT(flags & BUS_DMA_NOWAIT,
+               ("only BUS_DMA_NOWAIT is supported\n"));
+
        if (m0->m_pkthdr.len <= dmat->maxsize) {
                int first = 1;
                vm_paddr_t lastaddr = 0;
                struct mbuf *m;
 
-               nsegs = 1;
+               *nsegs = 1;
                error = 0;
                for (m = m0; m != NULL && error == 0; m = m->m_next) {
                        if (m->m_len == 0)
@@ -776,8 +806,9 @@ bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map,
 
                        error = _bus_dmamap_load_buffer(dmat, map,
                                        m->m_data, m->m_len,
+                                       segs, maxsegs,
                                        NULL, flags, &lastaddr,
-                                       &nsegs, first);
+                                       nsegs, first);
                        if (error == ENOMEM && !first) {
                                /*
                                 * Out of bounce pages due to too many
@@ -788,18 +819,15 @@ bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map,
                        }
                        first = 0;
                }
+#ifdef INVARIANTS
+               if (!error)
+                       KKASSERT(*nsegs <= maxsegs && *nsegs >= 1);
+#endif
        } else {
-               nsegs = 0;
+               *nsegs = 0;
                error = EINVAL;
        }
-
-       if (error) {
-               /* force "no valid mappings" in callback */
-               callback(callback_arg, dmat->segments, 0, 0, error);
-       } else {
-               callback(callback_arg, dmat->segments, nsegs,
-                        m0->m_pkthdr.len, error);
-       }
+       KKASSERT(error != EINPROGRESS);
        return error;
 }
 
@@ -854,6 +882,7 @@ bus_dmamap_load_uio(bus_dma_tag_t dmat, bus_dmamap_t map,
                caddr_t addr = (caddr_t) iov[i].iov_base;
 
                error = _bus_dmamap_load_buffer(dmat, map, addr, minlen,
+                               dmat->segments, dmat->nsegments,
                                pmap, flags, &lastaddr, &nsegs, first);
                first = 0;
 

diff --git a/sys/sys/bus_dma.h b/sys/sys/bus_dma.h
index 49c96e8..b1b3c03 100644 (file)
--- a/sys/sys/bus_dma.h
+++ b/sys/sys/bus_dma.h
@@ -243,6 +243,20 @@ int bus_dmamap_load_uio(bus_dma_tag_t dmat, bus_dmamap_t map,
                        int flags);
 
 /*
+ * Like bus_dmamap_load_mbuf without callback.
+ * Segmentation information are saved in 'segs' and 'nsegs' if
+ * the loading is successful.  'maxsegs' must be set by caller
+ * and must be at least 1 but less than 'dmat' nsegment.  It
+ * indicates the number of elements in 'segs'.  'flags' must
+ * have BUS_DMA_NOWAIT turned on.
+ */
+int
+bus_dmamap_load_mbuf_segment(bus_dma_tag_t dmat, bus_dmamap_t map,
+                            struct mbuf *mbuf,
+                            bus_dma_segment_t *segs, int maxsegs,
+                            int *nsegs, int flags);
+
+/*
  * Convenient function to create coherent busdma memory
  */
 int