doc: move README.NetConsole to HTML documentation

Convert README.NetConsole to reStructured text and move it to
doc/usage/netconsole.rst.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

2 files changed, 111 insertions, 0 deletions

diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index af7d50650df..063e9709819 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -3,6 +3,8 @@ Use U-Boot
 
 .. toctree::
 
+   netconsole
+
 Shell commands
 --------------
 
diff --git a/doc/usage/netconsole.rst b/doc/usage/netconsole.rst
new file mode 100644
index 00000000000..0156f0212d9
--- /dev/null
+++ b/doc/usage/netconsole.rst
@@ -0,0 +1,109 @@
+Network console
+===============
+
+In U-Boot, we implemented the networked console via the standard
+"devices" mechanism, which means that you can switch between the
+serial and network input/output devices by adjusting the 'stdin' and
+'stdout' environment variables. To switch to the networked console,
+set either of these variables to "nc". Input and output can be
+switched independently.
+
+The default buffer size can be overridden by setting
+CONFIG_NETCONSOLE_BUFFER_SIZE.
+
+We use an environment variable 'ncip' to set the IP address and the
+port of the destination. The format is <ip_addr>:<port>. If <port> is
+omitted, the value of 6666 is used. If the env var doesn't exist, the
+broadcast address and port 6666 are used. If it is set to an IP
+address of 0 (or 0.0.0.0) then no messages are sent to the network.
+The source / listening port can be configured separately by setting
+the 'ncinport' environment variable and the destination port can be
+configured by setting the 'ncoutport' environment variable.
+
+For example, if your server IP is 192.168.1.1, you could use::
+
+	=> setenv nc 'setenv stdout nc;setenv stdin nc'
+	=> setenv ncip 192.168.1.1
+	=> saveenv
+	=> run nc
+
+On the host side, please use this script to access the console
+
+.. code-block:: bash
+
+	tools/netconsole <ip> [port]
+
+The script uses netcat to talk to the board over UDP.  It requires you to
+specify the target IP address (or host name, assuming DNS is working). The
+script can be interrupted by pressing ^T (CTRL-T).
+
+Be aware that in some distributives (Fedora Core 5 at least)
+usage of nc has been changed and -l and -p options are considered
+as mutually exclusive. If nc complains about options provided,
+you can just remove the -p option from the script.
+
+It turns out that 'netcat' cannot be used to listen to broadcast
+packets. We developed our own tool 'ncb' (see tools directory) that
+listens to broadcast packets on a given port and dumps them to the
+standard output.  It will be built when compiling for a board which
+has CONFIG_NETCONSOLE defined.  If the netconsole script can find it
+in PATH or in the same directory, it will be used instead.
+
+For Linux, the network-based console needs special configuration.
+Minimally, the host IP address needs to be specified. This can be
+done either via the kernel command line, or by passing parameters
+while loading the netconsole.o module (when used in a loadable module
+configuration). Please refer to Documentation/networking/logging.txt
+file for the original Ingo Molnar's documentation on how to pass
+parameters to the loadable module.
+
+The format of the kernel command line parameter (for the static
+configuration) is as follows
+
+.. code-block:: bash
+
+    netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
+
+where
+
+src-port
+    source for UDP packets (defaults to 6665)
+
+src-ip
+    source IP to use (defaults to the interface's address)
+
+dev
+    network interface (defaults to eth0)
+
+tgt-port
+  port for logging agent (defaults to 6666)
+
+tgt-ip
+  IP address for logging agent (this is the required parameter)
+
+tgt-macaddr
+    ethernet MAC address for logging agent (defaults to broadcast)
+
+Examples
+
+.. code-block:: bash
+
+  netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
+  netconsole=@/,@192.168.3.1/
+
+Please note that for the Linux networked console to work, the
+ethernet interface has to be up by the time the netconsole driver is
+initialized. This means that in case of static kernel configuration,
+the respective Ethernet interface has to be brought up using the "IP
+Autoconfiguration" kernel feature, which is usually done by defaults
+in the ELDK-NFS-based environment.
+
+To browse the Linux network console output, use the 'netcat' tool invoked
+as follows:
+
+.. code-block:: bash
+
+	nc -u -l -p 6666
+
+Note that unlike the U-Boot implementation the Linux netconsole is
+unidirectional, i. e. you have console output only in Linux.