kernel-config: Check and repair kernel config after forcing options

Manually forcing kernel options with 'call_extensions_kernel_config()' can introduce missing dependencies or misconfigurations. This commit introduces a function which checks the config, re-establishes its sanity if necessary and outputs any changes to the user.
This also makes `./compile.sh kernel-config` (exiting without changes) and `./compile.sh rewrite-kernel-config` ouput the same config file. Previously, this was not the case.

lib/functions/compilation/kernel-config.sh

@@ -29,10 +29,16 @@ function kernel_config() {
 	[[ ! -d "${kernel_work_dir}" ]] && exit_with_error "kernel_work_dir does not exist: ${kernel_work_dir}"
 	declare previous_config_filename=".config.armbian.previous"
 	declare kernel_config_source_filename="" # which actual .config was used?
+	declare config_after_kernel_config_extension_filename=".config_after_kernel_config_extension"
 
 	LOG_SECTION="kernel_config_initialize" do_with_logging do_with_hooks kernel_config_initialize
 
 	if [[ "${KERNEL_CONFIGURE}" == "yes" ]]; then
+
+		# Check sanity of kernel config and repair the config if necessary
+		LOG_SECTION="kernel_config_check_and_repair" do_with_logging do_with_hooks kernel_config_check_and_repair
+
+		# Start interactive config menu unless running rewrite-kernel-config
 		if [[ "${ARMBIAN_COMMAND}" != "rewrite-kernel-config" ]]; then
 			# This piece is interactive, no logging
 			display_alert "Starting (interactive) kernel ${KERNEL_MENUCONFIG:-menuconfig}" "${LINUXCONFIG}" "debug"
@@ -78,6 +84,9 @@ function kernel_config_initialize() {
 	# Call the extensions. This is _also_ done during the kernel artifact's prepare_version, for consistent caching.
 	call_extensions_kernel_config
 
+	# Save the config state after the extensions forced some kernel options, for later checks
+	run_host_command_logged cp -pv ".config" "${config_after_kernel_config_extension_filename}"
+	
 	display_alert "Kernel configuration" "${LINUXCONFIG}" "info"
 }
 
@@ -89,6 +98,7 @@ function call_extensions_kernel_config() {
 		Instead, use `custom_kernel_config` which runs later and can undo anything done by this step.
 		Important: this hook might be run multiple times, and one of them might not have a .config in place.
 		Either way, the hook _must_ add representative changes to the `kernel_config_modifying_hashes` array, for kernel config hashing.
+		Please note: Manually changing options doesn't check the validity of the .config file. Check for warnings in your build log.
 	ARMBIAN_KERNEL_CONFIG
 
 	# Custom hooks receive a clean / updated config; depending on their modifications, they may need to run olddefconfig again.
@@ -99,6 +109,7 @@ function call_extensions_kernel_config() {
 		Armbian default Kconfig modifications have already been applied and can be overriden.
 		Important: this hook might be run multiple times, and one of them might not have a .config in place.
 		Either way, the hook _must_ add representative changes to the `kernel_config_modifying_hashes` array, for kernel config hashing.
+		Please note: Manually changing options doesn't check the validity of the .config file. Check for warnings in your build log.
 	CUSTOM_KERNEL_CONFIG
 }
 
@@ -138,3 +149,25 @@ function kernel_config_export() {
 		run_host_command_logged cp -pv defconfig "${kernel_config_source_filename}.defconfig"
 	fi
 }
+
+# Manually forcing kernel options with 'call_extensions_kernel_config()' can introduce missing dependencies or misconfigurations
+# This function checks the config, re-establishes its sanity if necessary and outputs any changes to the user
+function kernel_config_check_and_repair() {
+	# Re-run kernel make to automatically solve any dependencies and/or misconfigurations
+	run_kernel_make_dialog oldconfig
+
+	# Compare the previously saved config file with the current one
+	if cmp --silent "${kernel_work_dir}/.config" "${kernel_work_dir}/${config_after_kernel_config_extension_filename}"; then
+		# Do nothing if both files are the same
+		display_alert "No misconfigurations or missing kernel option dependencies detected" "info"
+	else
+		# Warn user and output diffs if make had to change anything because of missing dependencies or misconfigurations
+		display_alert "Forced kernel options introduced misconfigurations or missing dependencies!" "Please re-run rewrite-kernel-config" "warn"
+		display_alert "If this warning persists" "please remove dependent options using kernel-config or adapt your custom_kernel_config hooks" "warn"
+		display_alert "In some cases, the issue might also be" "misconfigured options in armbian_kernel_config hooks" "debug"
+
+		run_host_command_logged scripts/diffconfig "${config_after_kernel_config_extension_filename}" ".config"
+
+		display_alert "See options above which have been changed automatically" "to solve dependencies and/or misconfigurations" "warn"
+	fi
+}