[Buildroot] [PATCH] Make BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT public

[lists at philipp-wagner.com]

From: Philipp Wagner <philipp.wagner at tum.de>

Currently the BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT option is only
available as dependency. This option controls if the Linux build system
should build the DTB itself, or if buildroot explicitly calls the Linux
Makefile like "make something.dtb".

My use case: I want to build an OpenRISC image with a custom device tree
file. OpenRISC does not support appended DTBs, and I'm not using a
bootloader, but link everything into a single kernel (vmlinux) image.

The kernel option CONFIG_OPENRISC_BUILTIN_DTB allows me to specify a dtb
file, which is typically located in the kernel source tree in
arch/openrisc/boot/dts/NAME.dts.

Since my dts file is not part of the upstream kernel, I have two
options: either patch the kernel to include the DTS file, and then
specify it using the CONFIG_OPENRISC_BUILTIN_DTB option.

Or use buildroot's BR2_LINUX_KERNEL_CUSTOM_DTS_PATH config option to
copy any DTS file to the kernel source tree, and then specify this file
with CONFIG_OPENRISC_BUILTIN_DTB as before.

However, the second option also requries the buildroot option
BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT to be set, otherwise I end up with a
"make -C kerneldir NAME.dts" call, which doesn't work (no such target
exists).

Currently the BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT option exists, but it's
not visible/available. Simply making it available solves the problem for
me nicely.
---
 linux/Config.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/linux/Config.in b/linux/Config.in
index ecb12d0b16..1f02ee6e3b 100644
--- a/linux/Config.in
+++ b/linux/Config.in
@@ -373,7 +373,7 @@ if BR2_LINUX_KERNEL_DTS_SUPPORT
 # The variable below address the second case, were you only want
 # limited actions from buildroot.
 config BR2_LINUX_KERNEL_DTB_IS_SELF_BUILT
-	bool
+	bool "DTB is built by kernel itself"
 
 config BR2_LINUX_KERNEL_APPENDED_DTB
 	bool
-- 
2.19.1