shell: Enable backends via Kconfig file

Added functionality to enable active shell backends via Kconfig
file. When there will be more backends implemented user will
have an option to select only required ones.

It is no longer needed to select SERIAL in prj.conf.

Fixes #10190

Signed-off-by: Jakub Rzeszutko <jakub.rzeszutko@nordicsemi.no>

samples/subsys/shell/shell_module/prj.conf

@@ -1,6 +1,5 @@
 CONFIG_PRINTK=y
 CONFIG_SHELL=y
-CONFIG_SERIAL=y
 CONFIG_LOG=y
 CONFIG_LOG_BACKEND_UART=n
 CONFIG_KERNEL_SHELL=y

subsys/shell/CMakeLists.txt

@@ -16,6 +16,10 @@ zephyr_sources_ifdef(
   shell_fprintf.c
   shell_utils.c
   shell_ops.c
+  )
+
+zephyr_sources_ifdef(
+  CONFIG_SHELL_BACKEND_SERIAL
   shell_uart.c
   )
 

subsys/shell/Kconfig

@@ -38,13 +38,13 @@ menuconfig SHELL
 	bool "Enable shell"
 	select LOG_RUNTIME_FILTERING
 	select POLL
-	depends on SERIAL
 
 if SHELL
 
 module = SHELL
 module-str = Shell
 source "subsys/logging/Kconfig.template.log_config"
+source "subsys/shell/Kconfig.backends"
 
 config SHELL_STACK_SIZE
 	int "Shell thread stack size"

subsys/shell/Kconfig.backends

@@ -0,0 +1,25 @@
+# Kconfig.backends - Shell badckends configuration options
+
+#
+# Copyright (c) 2018 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+menuconfig SHELL_BACKENDS
+	bool "Enable shell backends"
+	default y
+	help
+	  Enable shell backends.
+
+if SHELL_BACKENDS
+
+config SHELL_BACKEND_SERIAL
+	bool "Enable serial backends."
+	default y
+	select SERIAL
+	help
+	  Enable serial backends.
+
+endif # SHELL_BACKENDS
+