segger: rtt: disable unsupported shell/log features

The RTT backend of the shell does not support several of the more
advanced terminal features. This commit proposes to inactivate these
features by default when RTT is selected as shell backend.

Signed-off-by: Florian Grandel <fgrandel@code-for-humans.de>

modules/segger/Kconfig

@@ -38,6 +38,7 @@ config SEGGER_RTT_BUFFER_SIZE_UP
 
 config SEGGER_RTT_BUFFER_SIZE_DOWN
 	int "Size of the buffer for terminal input of target, from host"
+	default 32 if SHELL_BACKEND_RTT
 	default 16
 
 config SEGGER_RTT_PRINTF_BUFFER_SIZE

subsys/logging/backends/Kconfig.uart

@@ -4,7 +4,7 @@
 config LOG_BACKEND_UART
 	bool "UART backend"
 	depends on UART_CONSOLE
-	default y if !SHELL_BACKEND_SERIAL
+	default y if !SHELL_BACKEND_SERIAL && !SHELL_BACKEND_RTT
 	select LOG_OUTPUT
 	help
 	  When enabled backend is using UART to output logs.

subsys/shell/Kconfig

@@ -90,7 +90,7 @@ config SHELL_ARGC_MAX
 
 config SHELL_TAB
 	bool "The Tab button support in shell"
-	default y if !SHELL_MINIMAL
+	default y if !SHELL_MINIMAL && !SHELL_BACKEND_RTT
 	help
 	  Enable using the Tab button in the shell. The button
 	  can be used for prompting commands, or for autocompletion.
@@ -125,7 +125,7 @@ config SHELL_START_OBSCURED
 
 config SHELL_VT100_COMMANDS
 	bool "VT100 commands in shell"
-	default y
+	default y if !SHELL_BACKEND_RTT
 	help
 	  Enables VT100 commands in shell (e.g. cursor position, clear screen etc.).
 

subsys/shell/backends/Kconfig.backends

@@ -16,6 +16,8 @@ DT_CHOSEN_Z_SHELL_UART := zephyr,shell-uart
 
 config SHELL_BACKEND_SERIAL
 	bool "Serial backend"
+	# Serial (UART) requires interrupts and the RTT backend cannot be used from an ISR context.
+	default n if SHELL_BACKEND_RTT
 	default "$(dt_chosen_enabled,$(DT_CHOSEN_Z_SHELL_UART))" if HAS_DTS
 	default y if !HAS_DTS
 	select SERIAL