doc: shell: add information about dummy backend

Shell documentation has been updated with information about new
backend called DUMMY.

Signed-off-by: Jakub Rzeszutko <[email protected]>

Author: Jakub Rzeszutko

doc/subsystems/shell/shell.rst

@@ -31,6 +31,7 @@ The module can be connected to any transport for command input and output.
 At this point, the following transport layers are implemented:
 
 * UART
+* DUMMY - not a physical transport layer
 
 See the :ref:`shell_api` documentation for more information.
 
@@ -168,6 +169,27 @@ that is found deepest in the command tree and further subcommands (without a
 handler) are passed as arguments. Characters within parentheses are treated
 as one argument. If shell wont find a handler it will display an error message.
 
+Commands can be also executed from a user application using any active backend
+and a function :cpp:func:`shell_execute_cmd`, as shown in this example:
+
+.. code-block:: c
+
+	void main(void)
+	{
+		/* Below code will execute "clear" command on a DUMMY backend */
+		shell_execute_cmd(NULL, "clear");
+
+		/* Below code will execute "shell colors off" command on
+		 * an UART backend
+		 */
+		shell_execute_cmd(shell_backend_uart_get_ptr(),
+				  "shell colors off");
+	}
+
+Enable the DUMMY backend by setting the Kconfig
+:option:`CONFIG_SHELL_BACKEND_DUMMY` option.
+
+
 Command handler
 ----------------
 

subsys/shell/Kconfig.backends

@@ -23,10 +23,8 @@ config SHELL_BACKEND_SERIAL
 
 config SHELL_BACKEND_DUMMY
 	bool "Enable dummy backend."
-	select SERIAL
 	help
-	  Enable dummy backend which can be used to test commands with no need
-	  for physical transport interface.
+	  Enable dummy backend which can be used to execute commands with no
+	  need for physical transport interface.
 
 endif # SHELL_BACKENDS
-

subsys/shell/shell_dummy.c

@@ -31,8 +31,8 @@ static int uninit(const struct shell_transport *transport)
 {
 	struct shell_dummy *sh_dummy = (struct shell_dummy *)transport->ctx;
 
-	if (sh_dummy->initialized == false) {
-		return -EINVAL;
+	if (!sh_dummy->initialized) {
+		return -ENODEV;
 	}
 
 	sh_dummy->initialized = false;
@@ -44,8 +44,8 @@ static int enable(const struct shell_transport *transport, bool blocking)
 {
 	struct shell_dummy *sh_dummy = (struct shell_dummy *)transport->ctx;
 
-	if (sh_dummy->initialized == false) {
-		return -EINVAL;
+	if (!sh_dummy->initialized) {
+		return -ENODEV;
 	}
 
 	return 0;
@@ -58,7 +58,7 @@ static int write(const struct shell_transport *transport,
 
 	if (!sh_dummy->initialized) {
 		*cnt = 0;
-		return -EINVAL;
+		return -ENODEV;
 	}
 
 	*cnt = length;
@@ -70,9 +70,8 @@ static int read(const struct shell_transport *transport,
 {
 	struct shell_dummy *sh_dummy = (struct shell_dummy *)transport->ctx;
 
-
-	if (sh_dummy->initialized) {
-		return -EINVAL;
+	if (!sh_dummy->initialized) {
+		return -ENODEV;
 	}
 
 	*cnt = 0;