task #7013: Added option LWIP_NETIF_TX_SINGLE_PBUF to try to create transmit packets from only one pbuf to help MACs that don't support scatter-gather DMA.

CHANGELOG

@@ -19,6 +19,11 @@ HISTORY
 
   ++ New features:
 
+  2009-05-10 Simon Goldschmidt
+  * opt.h, sockets.c, pbuf.c, netbuf.h, pbuf.h: task #7013: Added option
+    LWIP_NETIF_TX_SINGLE_PBUF to try to create transmit packets from only
+    one pbuf to help MACs that don't support scatter-gather DMA.
+
   2009-05-09 Simon Goldschmidt
   * icmp.h, icmp.c: Shrinked ICMP code, added option to NOT check icoming
     ECHO pbuf for size (just use it): LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN

src/api/sockets.c

@@ -668,7 +668,7 @@ lwip_sendto(int s, const void *data, size_t size, int flags,
 {
   struct lwip_socket *sock;
   struct ip_addr remote_addr;
-  int err;
+  err_t err;
   u16_t short_size;
 #if !LWIP_TCPIP_CORE_LOCKING
   struct netbuf buf;
@@ -738,17 +738,25 @@ lwip_sendto(int s, const void *data, size_t size, int flags,
               s, data, short_size, flags));
   ip_addr_debug_print(SOCKETS_DEBUG, &remote_addr);
   LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F"\n", remote_port));
-    
+
   /* make the buffer point to the data that should be sent */
-  if ((err = netbuf_ref(&buf, data, short_size)) == ERR_OK) {
+#if LWIP_NETIF_TX_SINGLE_PBUF
+  /* Allocate a new netbuf and copy the data into it. */
+  if (netbuf_alloc(&buf, short_size) == NULL) {
+    err = ERR_MEM;
+  } else {
+    err = netbuf_take(&buf, data, short_size);
+  }
+#else /* LWIP_NETIF_TX_SINGLE_PBUF */
+  err = netbuf_ref(&buf, data, short_size);
+#endif /* LWIP_NETIF_TX_SINGLE_PBUF */
+  if (err == ERR_OK) {
     /* send the data */
     err = netconn_send(sock->conn, &buf);
   }
 
   /* deallocated the buffer */
-  if (buf.p != NULL) {
-    pbuf_free(buf.p);
-  }
+  netbuf_free(&buf);
 #endif /* LWIP_TCPIP_CORE_LOCKING */
   sock_set_errno(sock, err_to_errno(err));
   return (err == ERR_OK ? short_size : -1);

src/core/pbuf.c

@@ -790,8 +790,8 @@ pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
   u16_t buf_copy_len;
   u16_t copied_total = 0;
 
-  LWIP_ERROR("netbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
-  LWIP_ERROR("netbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
+  LWIP_ERROR("pbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
+  LWIP_ERROR("pbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
 
   left = 0;
 
@@ -819,3 +819,76 @@ pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
   }
   return copied_total;
 }
+
+/**
+ * Copy application supplied data into a pbuf.
+ * This function can only be used to copy the equivalent of buf->tot_len data.
+ *
+ * @param buf pbuf to fill with data
+ * @param dataptr application supplied data buffer
+ * @param len length of the application supplied data buffer
+ *
+ * @return ERR_OK if successful, ERR_MEM if the pbuf is not big enough
+ */
+err_t
+pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len)
+{
+  struct pbuf *p;
+  u16_t buf_copy_len;
+  u16_t total_copy_len = len;
+  u16_t copied_total = 0;
+
+  LWIP_ERROR("pbuf_take: invalid buf", (buf != NULL), return 0;);
+  LWIP_ERROR("pbuf_take: invalid dataptr", (dataptr != NULL), return 0;);
+
+  if ((buf == NULL) || (dataptr == NULL) || (buf->tot_len < len)) {
+    return ERR_ARG;
+  }
+
+  /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
+  for(p = buf; total_copy_len != 0; p = p->next) {
+    LWIP_ASSERT("pbuf_take: invalid pbuf", p != NULL);
+    buf_copy_len = total_copy_len;
+    if (buf_copy_len > p->len) {
+      /* this pbuf cannot hold all remaining data */
+      buf_copy_len = p->len;
+    }
+    /* copy the necessary parts of the buffer */
+    MEMCPY(p->payload, &((char*)dataptr)[copied_total], buf_copy_len);
+    total_copy_len -= buf_copy_len;
+    copied_total += buf_copy_len;
+  }
+  LWIP_ASSERT("did not copy all data", total_copy_len == 0 && copied_total == len);
+  return ERR_OK;
+}
+
+/**
+ * Creates a single pbuf out of a queue of pbufs.
+ *
+ * @remark: The source pbuf 'p' is not freed by this function because that can
+ *          be illegal in some places!
+ *
+ * @param p the source pbuf
+ * @param layer pbuf_layer of the new pbuf
+ *
+ * @return a new, single pbuf (p->next is NULL)
+ *         or the old pbuf if allocation fails
+ */
+struct pbuf*
+pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
+{
+  struct pbuf *q;
+  err_t err;
+  if (p->next == NULL) {
+    return p;
+  }
+  q = pbuf_alloc(layer, p->tot_len, PBUF_RAM);
+  if (q == NULL) {
+    /* @todo: what do we do now? */
+    return p;
+  }
+  err = pbuf_copy(q, p);
+  LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
+  pbuf_free(p);
+  return q;
+}

src/include/lwip/netbuf.h

@@ -65,6 +65,7 @@ void              netbuf_first    (struct netbuf *buf);
 #define netbuf_copy_partial(buf, dataptr, len, offset) \
   pbuf_copy_partial((buf)->p, (dataptr), (len), (offset))
 #define netbuf_copy(buf,dataptr,len) netbuf_copy_partial(buf, dataptr, len, 0)
+#define netbuf_take(buf, dataptr, len) pbuf_take((buf)->p, dataptr, len)
 #define netbuf_len(buf)              ((buf)->p->tot_len)
 #define netbuf_fromaddr(buf)         ((buf)->addr)
 #define netbuf_fromport(buf)         ((buf)->port)

src/include/lwip/opt.h

@@ -965,6 +965,19 @@
 #define LWIP_NETIF_LOOPBACK_MULTITHREADING    (!NO_SYS)
 #endif
 
+/**
+ * LWIP_NETIF_TX_SINGLE_PBUF: if this is set to 1, lwIP tries to put all data
+ * to be sent into one single pbuf. This is for compatibility with DMA-enabled
+ * MACs that do not support scatter-gather.
+ * Beware that this might involve CPU-memcpy before transmitting that would not
+ * be needed without this flag! Use this only if you need to!
+ *
+ * @todo: TCP and IP-frag do not work with this, yet:
+ */
+#ifndef LWIP_NETIF_TX_SINGLE_PBUF
+#define LWIP_NETIF_TX_SINGLE_PBUF             0
+#endif /* LWIP_NETIF_TX_SINGLE_PBUF */
+
 /*
    ------------------------------------
    ---------- LOOPIF options ----------

src/include/lwip/pbuf.h

@@ -110,6 +110,8 @@ void pbuf_chain(struct pbuf *head, struct pbuf *tail);
 struct pbuf *pbuf_dechain(struct pbuf *p);
 err_t pbuf_copy(struct pbuf *p_to, struct pbuf *p_from);
 u16_t pbuf_copy_partial(struct pbuf *p, void *dataptr, u16_t len, u16_t offset);
+err_t pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len);
+struct pbuf *pbuf_coalesce(struct pbuf *p, pbuf_layer layer);
 
 #ifdef __cplusplus
 }