preboot: Introduce CONFIG_USE_PREBOOT and migrate CONFIG_PREBOOT
This is the same migration path as commit b6251db8c3f0 ("Kconfig:
Introduce USE_BOOTCOMMAND and migrate BOOTCOMMAND").
I also moved the description in README to the Kconfig help.
I ripped off the sentence about 'LWMON' since it is gone already.
I only let my boards migrate, leaving the rest to platform maintainers.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/common/Kconfig b/common/Kconfig
index e100c22..1a1951f 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -232,6 +232,24 @@
This is the string of commands that will be used as bootcmd and if
AUTOBOOT is set, automatically run.
+config USE_PREBOOT
+ bool "Enable preboot"
+ help
+ When this option is enabled, the existence of the environment
+ variable "preboot" will be checked immediately before starting the
+ CONFIG_BOOTDELAY countdown and/or running the auto-boot command resp.
+ entering interactive mode.
+
+ This feature is especially useful when "preboot" is automatically
+ generated or modified. For example, the boot code can modify the
+ "preboot" when a user holds down a certain combination of keys.
+
+config PREBOOT
+ string "preboot default value"
+ depends on USE_PREBOOT
+ help
+ This is the default of "preboot" environment variable.
+
menu "Console"
config MENU