[PATCH 2/3] Kbuild: Implement CONFIG_UIMAGE_KERNEL_NOLOAD

This allows the user to use U-Boot's mkimage's -T kernel_noload option
if their arch Kconfig allows it, and they desire.

Signed-off-by: Stephen Warren <redacted>
---
The next patch enables this new CONFIG_ALLOW_ option for ARM. I assume
that some other architectures will also be able to enable it, but I'm
not familiar enough with any to know which.

 init/Kconfig         |   15 +++++++++++++++
 scripts/Makefile.lib |   15 ++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 6cfd71d..2035562 100644
--- a/init/Kconfig
+++ b/init/Kconfig

@@ -203,6 +203,21 @@ config KERNEL_LZO
 
 endchoice
 
+config ALLOW_UIMAGE_KERNEL_NOLOAD
+	bool
+
+config UIMAGE_KERNEL_NOLOAD
+	bool "Use mkimage's -T kernel_noload instead of -T kernel"
+	depends on ALLOW_UIMAGE_KERNEL_NOLOAD
+	help
+	  uImage files of type "kernel" embed an absolute load and entry point
+	  address. If the uImage is loaded to a different address, then the
+	  image must be copied the uImage file to the specified load address.
+	  This copy is a waste of time if the uImage is in fact completely
+	  relocatable. If your kernel and bootloader support it, you can build
+	  a "kernel_noload" uImage rather than a "kernel" uImage, which
+	  prevents any such copying. If unsure say N.
+
 config DEFAULT_HOSTNAME
 	string "Default hostname"
 	default "(none)"

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 7b0be18..d9c1c87 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib

@@ -314,9 +314,18 @@ MKIMAGE := $(srctree)/scripts/mkuboot.sh
 UIMAGE_ARCH = $(SRCARCH)
 UIMAGE_COMPRESSION = $(if $(2),$(2),none)
 UIMAGE_OPTS-y =
-UIMAGE_TYPE = kernel
-UIMAGE_LOADADDR=arch_must_set_this
-UIMAGE_ENTRYADDR=$(UIMAGE_LOADADDR)
+ifeq ($(CONFIG_UIMAGE_KERNEL_NOLOAD),y)
+  UIMAGE_TYPE = kernel_noload
+  # Unused by bootloader:
+  UIMAGE_LOADADDR=0
+  # Entry point relative to actual load address:
+  UIMAGE_ENTRYADDR=0
+else
+  UIMAGE_TYPE = kernel
+  # Absolute addresses:
+  UIMAGE_LOADADDR=arch_must_set_this
+  UIMAGE_ENTRYADDR=$(UIMAGE_LOADADDR)
+endif
 UIMAGE_NAME = 'Linux-$(KERNELRELEASE)'
 UIMAGE_IN = $<
 UIMAGE_OUT = $@