When trying to use the exact same device tree source to build the dtbs used with U-Boot and linux, one often runs into various problems. For example, files under include/dt-bindings/ might not be completely in sync, so some #defines are available in linux but not in U-Boot.
It's also possible that there are nodes/hardware one simply doesn't need or want to describe to U-Boot, e.g. to reduce the size of the .dtb (for SPL, there's already the whole fdtgrep machinery to deal with that, but not for U-Boot proper), or configuration settings like watchdog timeout one wants to make different between linux and U-Boot.
So in order to allow such tweaks, add an explicit define of the macro __U_BOOT__. Since U-Boot includes linux/kconfig.h (and defines __ASSEMBLY__ to make that work) while linux doesn't, one could also use __ASSEMBLY__ or just about any known-to-be-defined CONFIG_* macro as a proxy, but it's much more readable, maintainable and robust if one's .dts has "ifdef __U_BOOT__" rather than "ifdef __ASSEMBLY__".
Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk --- scripts/Makefile.lib | 1 + 1 file changed, 1 insertion(+)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 3db2550085..4183767a62 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -190,6 +190,7 @@ dtc_cpp_flags = -Wp,-MD,$(depfile).pre.tmp -nostdinc \ -I$(srctree)/arch/$(ARCH)/dts/include \ -I$(srctree)/include \ -D__ASSEMBLY__ \ + -D__U_BOOT__ \ -undef -D__DTS__
# Finds the multi-part object the current object will be linked into