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kbuild: create a rule to run the pre-processor on *.dts files

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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 <sjg@chromium.org>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Michal Marek <mmarek@suse.cz>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Stephen Warren 2013-02-05 12:06:28 -07:00 committed by Grant Likely
parent 1d0b1c74ed
commit 22435f3833
2 changed files with 33 additions and 0 deletions
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23
Documentation/kbuild/makefiles.txt
View File

@ -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

10
scripts/Makefile.lib
View File

@ -269,6 +269,16 @@ cmd_dtc = $(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 $(DTC_FLAGS) -d $(depfile
$(obj)/%.dtb: $(src)/%.dts FORCE
$(call if_changed_dep,dtc)
dtc-tmp = $(subst $(comma),_,$(dot-target).dts)
quiet_cmd_dtc_cpp = DTC+CPP $@
cmd_dtc_cpp = $(CPP) $(cpp_flags) -x assembler-with-cpp -undef -D__DTS__ \
-o $(dtc-tmp) $< ; \
$(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 $(DTC_FLAGS) $(dtc-tmp)
$(obj)/%.dtb: $(src)/%.dtsp FORCE
$(call if_changed_dep,dtc_cpp)
# Bzip2
# ---------------------------------------------------------------------------