From b83f28b91190b6fe558dc1fb440beb33210624a8 Mon Sep 17 00:00:00 2001
From: Sepherosa Ziehau <sephe@dragonflybsd.org>
Date: Sun, 18 Jan 2009 11:56:03 +0800
Subject: [PATCH] busdma(9): Add bus_dmamap_load_mbuf_defrag()

This function is mainly used to avoid code duplication in various
(should be many) NIC driver code.
---
 sys/kern/subr_busdma.c | 27 +++++++++++++++++++++++++++
 sys/sys/bus_dma.h      | 11 +++++++++++
 2 files changed, 38 insertions(+)

diff --git a/sys/kern/subr_busdma.c b/sys/kern/subr_busdma.c
index e5cee385f7..a9bb313b12 100644
--- a/sys/kern/subr_busdma.c
+++ b/sys/kern/subr_busdma.c
@@ -35,6 +35,7 @@
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/bus_dma.h>
+#include <sys/mbuf.h>
 
 static void
 _bus_dmamem_coherent_cb(void *arg, bus_dma_segment_t *segs, int nseg, int error)
@@ -91,3 +92,29 @@ bus_dmamem_coherent(bus_dma_tag_t parent,
 	}
 	return 0;
 }
+
+int
+bus_dmamap_load_mbuf_defrag(bus_dma_tag_t dmat, bus_dmamap_t map,
+			    struct mbuf **m_head,
+			    bus_dma_segment_t *segs, int maxsegs,
+			    int *nsegs, int flags)
+{
+	struct mbuf *m = *m_head;
+	int error;
+
+	error = bus_dmamap_load_mbuf_segment(dmat, map, m,
+			segs, maxsegs, nsegs, flags);
+	if (error == EFBIG) {
+		struct mbuf *m_new;
+
+		m_new = m_defrag(m, MB_DONTWAIT);
+		if (m_new == NULL)
+			return ENOBUFS;
+		else
+			*m_head = m = m_new;
+
+		error = bus_dmamap_load_mbuf_segment(dmat, map, m,
+				segs, maxsegs, nsegs, BUS_DMA_NOWAIT);
+	}
+	return error;
+}
diff --git a/sys/sys/bus_dma.h b/sys/sys/bus_dma.h
index b1b3c03c25..b4fe07d0e2 100644
--- a/sys/sys/bus_dma.h
+++ b/sys/sys/bus_dma.h
@@ -256,6 +256,17 @@ bus_dmamap_load_mbuf_segment(bus_dma_tag_t dmat, bus_dmamap_t map,
 			     bus_dma_segment_t *segs, int maxsegs,
 			     int *nsegs, int flags);
 
+/*
+ * Like bus_dmamap_load_mbuf_segment, but it will call m_defrag()
+ * and try reloading if low level code indicates too many fragments
+ * in the '*mbuf'; 'mbuf' will be updated under this situation.
+ */
+int
+bus_dmamap_load_mbuf_defrag(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
  */
-- 
2.41.0