Make skiboot version configurable

This allows us to specify both a global default stable skiboot version
(like we've been doing up until now), or, on a per platform (or build)
basis, build a different skiboot version.

Initially, this will be used to build garrison with skiboot master
rather than with 5.1.x

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/package/skiboot/Config.in b/openpower/package/skiboot/Config.in
index e1f571d..6b5ae0b 100644
--- a/openpower/package/skiboot/Config.in
+++ b/openpower/package/skiboot/Config.in
@@ -1,3 +1,4 @@
+menu "Skiboot"
 
 config BR2_TARGET_SKIBOOT
 	bool "skiboot"
@@ -12,4 +13,28 @@
 	bool "Embed kernel payload in skiboot image"
 	depends on BR2_LINUX_KERNEL_ZIMAGE_EPAPR
 
+choice
+	prompt "Skiboot version"
+	default BR2_SKIBOOT_LATEST_VERSION
+
+config BR2_SKIBOOT_LATEST_VERSION
+	bool "Use skiboot stable"
+
+config BR2_SKIBOOT_CUSTOM_VERSION
+	bool "Custom version"
+
+endchoice
+
+config BR2_SKIBOOT_CUSTOM_VERSION_VALUE
+	string "skiboot version"
+	depends on BR2_SKIBOOT_CUSTOM_VERSION
+
+config BR2_SKIBOOT_VERSION
+	string
+	default "skiboot-5.1.8" if BR2_SKIBOOT_LATEST_VERSION
+	default BR2_SKIBOOT_CUSTOM_VERSION_VALUE \
+		if BR2_SKIBOOT_CUSTOM_VERSION
+
 endif
+
+endmenu
diff --git a/openpower/package/skiboot/skiboot.mk b/openpower/package/skiboot/skiboot.mk
index b550b8d..90b2110 100644
--- a/openpower/package/skiboot/skiboot.mk
+++ b/openpower/package/skiboot/skiboot.mk
@@ -4,7 +4,8 @@
 #
 ################################################################################
 
-SKIBOOT_VERSION = skiboot-5.1.8
+SKIBOOT_VERSION = $(call qstrip,$(BR2_SKIBOOT_VERSION))
+
 SKIBOOT_SITE = $(call github,open-power,skiboot,$(SKIBOOT_VERSION))
 SKIBOOT_INSTALL_IMAGES = YES
 SKIBOOT_INSTALL_TARGET = NO