shell: Parametrize dummy shell buffer size

The commit adds Kconfig option to configure dummy shell buffer size.
Size of this buffer determines how mutch of command output will be
stored in buffer.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

include/shell/shell_dummy.h

@@ -24,7 +24,7 @@ struct shell_dummy {
 	size_t len;
 
 	/** output buffer to collect shell output */
-	char buf[300];
+	char buf[CONFIG_SHELL_BACKEND_DUMMY_BUF_SIZE];
 };
 
 #define SHELL_DUMMY_DEFINE(_name)					\

subsys/shell/Kconfig.backends

@@ -291,11 +291,21 @@ config SHELL_BACKEND_DUMMY
 	  Enable dummy backend which can be used to execute commands with no
 	  need for physical transport interface.
 
+if SHELL_BACKEND_DUMMY
+
 config SHELL_PROMPT_DUMMY
 	string "Displayed prompt name"
-	depends on SHELL_BACKEND_DUMMY
 	default "~$ "
 	help
 	  Displayed prompt name for DUMMY backend.
 
+config SHELL_BACKEND_DUMMY_BUF_SIZE
+	int "Size of dummy buffer size"
+	default 300
+	help
+	  This is size of output buffer that will be used by dummy backend, this limits number of
+	  characters that will be captured from command output.
+
+endif # SHELL_BACKEND_DUMMY
+
 endif # SHELL_BACKENDS

subsys/shell/shell.c

@@ -8,7 +8,9 @@
 #include <stdlib.h>
 #include <sys/atomic.h>
 #include <shell/shell.h>
+#if defined(CONFIG_SHELL_BACKEND_DUMMY)
 #include <shell/shell_dummy.h>
+#endif
 #include "shell_ops.h"
 #include "shell_help.h"
 #include "shell_utils.h"