From 22435f38337ef6a8abb33574604e77c335b75d14 Mon Sep 17 00:00:00 2001 From: Stephen Warren Date: Tue, 5 Feb 2013 12:06:28 -0700 Subject: kbuild: create a rule to run the pre-processor on *.dts files Create cmd_dtc_cpp to run the C pre-processor on *.dts file before passing them to dtc for final compilation. This allows the use of #define and #include within the .dts file. Acked-by: Simon Glass Acked-by: Jean-Christophe PLAGNIOL-VILLARD Acked-by: Michal Marek Acked-by: Srinivas Kandagatla Signed-off-by: Stephen Warren Signed-off-by: Grant Likely --- Documentation/kbuild/makefiles.txt | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'Documentation/kbuild') diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 14c3f4f1b617..5198b742fde1 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -1186,6 +1186,29 @@ When kbuild executes, the following steps are followed (roughly): clean-files += *.dtb DTC_FLAGS ?= -p 1024 + dtc_cpp + This is just like dtc as describe above, except that the C pre- + processor is invoked upon the .dtsp file before compiling the result + with dtc. + + In order for build dependencies to work, all files compiled using + dtc_cpp must use the C pre-processor's #include functionality and not + dtc's /include/ functionality. + + Using the C pre-processor allows use of #define to create named + constants. In turn, the #defines will typically appear in a header + file, which may be shared with regular C code. Since the dtc language + represents a data structure rather than code in C syntax, similar + restrictions are placed on a header file included by a device tree + file as for a header file included by an assembly language file. + In particular, the C pre-processor is passed -x assembler-with-cpp, + which sets macro __ASSEMBLY__. __DTS__ is also set. These allow header + files to restrict their content to that compatible with device tree + source. + + A central rule exists to create $(obj)/%.dtb from $(src)/%.dtsp; + architecture Makefiles do no need to explicitly write out that rule. + --- 6.8 Custom kbuild commands When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand -- cgit v1.2.1