apps/ make changes + SLIP MTU notes

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3381 42af7a65-404d-4744-a932-0658087f49c3

TODO

@@ -309,13 +309,18 @@ o Network (net/, drivers/net)
                function so that little of this incompatibilities need be exposed.
 
   Description: The SLIP driver (drivers/net/slip.c) has had only the most superficial
-               testing.  The main issue is the I haven't yet gotten a dual UART Linux
+               testing.  Issues/Notes:
-               configuration that supports SLIP (I need one UART for SLIP and one for
+               (1) The main issue is the I haven't yet gotten a dual UART Linux
-               the serial debug console).  A second issue is that SLIP requires
+                   configuration that supports SLIP (I need one UART for SLIP and
-               hardware handshake and that has not been implemented in the UART
+                   one for the serial debug console).
-               drivers on most platforms.  It might be possible to use a special
+               (2) A second issue is that SLIP requires hardware handshake and
-               cable to bypass the handshaking (but which may also result in data
+                   that has not been implemented in the UART drivers on most platforms.
-               overrun errors).
+                   It might be possible to use a special cable to bypass the handshaking.
+                   Tiy might also try the slattach' option -L which is supposed to
+                   enable "3-wire operation."  Either action which may also result in
+                   data overrun errors).
+               (3) Finally, the Linux slip driver is hard-coded to use an MTU of 296
+                   so setting CONFIG_NET_BUFSIZE to a 296 is also advised.
   Status:      Open
   Priority:    Medium
 

configs/olimex-lpc1766stk/README.txt

@@ -816,16 +816,15 @@ Where <subdir> is one of the following:
        This should create an interface with a name like sl0, or sl1, etc.
        Add -d to get debug output.  This will show the interface name.
 
+       NOTE: The Linux slip module hard-codes its MTU size to 296.  So you
+       might as well set CONFIG_NET_BUFSIZE to 296 as well.
+
     4. After turning over the line to the SLIP driver, you must configure
        the network interface. Again, you do this using the standard
        ifconfig and route commands. Assume that we have connected to a
        host PC with address 192.168.0.101 from your target with address
        10.0.0.2. On the Linux PC you would execute the following as root:
 
-       $ ifconfig sl0 10.0.0.2/24 up
-
-       Or maybe,
-
        $ ifconfig sl0 10.0.0.1 pointopoint 10.0.0.2 up
        $ route add 10.0.0.2 dev sl0
 
@@ -835,6 +834,10 @@ Where <subdir> is one of the following:
 
        $ tcpdump -n -nn -i sl0 -x -X -s 1500
 
+    NOTES:  Only UART1 supports the hardware handshake.  If hardware
+    handshake is not available, then you might try the slattach option
+    -L which is supposed to enable "3-wire operation."
+
   thttpd:
     This builds the THTTPD web server example using the THTTPD and
     the examples/thttpd application.

configs/olimex-lpc1766stk/slip-httpd/defconfig

@@ -552,7 +552,7 @@ CONFIG_NET_MULTIBUFFER=y
 CONFIG_NET_IPv6=n
 CONFIG_NSOCKET_DESCRIPTORS=16
 CONFIG_NET_SOCKOPTS=y
-CONFIG_NET_BUFSIZE=420
+CONFIG_NET_BUFSIZE=296
 CONFIG_NET_TCP=y
 CONFIG_NET_TCP_CONNS=16
 CONFIG_NET_NTCP_READAHEAD_BUFFERS=8

drivers/net/slip.c

@@ -67,6 +67,11 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
+/* NOTE:  Slip requires UART hardware handshake.  If hardware handshake is
+ * not available with your UART, then you might try the 'slattach' option
+ * -L which is supposed to enable "3-wire operation."
+ */
+
 /* Configuration ************************************************************/
 
 #if UIP_LLH_LEN > 0
@@ -85,6 +90,14 @@
 #  define CONFIG_SLIP_DEFPRIO 128
 #endif
 
+/* The Linux slip module hard-codes its MTU size to 296.  So you
+       might as well set CONFIG_NET_BUFSIZE to 296 as well.
+#if CONFIG_NET_BUFSIZE < 296
+#  error "CONFIG_NET_BUFSIZE >= 296 is required"
+#elif CONFIG_NET_BUFSIZE > 296
+#  warning "CONFIG_NET_BUFSIZE == 296 is optimal"
+#endif
+
 /*  SLIP special character codes *******************************************/
 
 #define SLIP_END      0300    /* Indicates end of packet */