On 05/29/2013 09:59 AM, Simon Glass wrote:
Hi Stephen,
On Tue, May 28, 2013 at 1:57 PM, Stephen Warren swarren@wwwdotorg.org wrote:
On 05/28/2013 01:36 PM, Simon Glass wrote:
There are a few partially conflicting requirements in compiling the device tree, since U-Boot relies on whatever is installed on the build machine.
Some versions of dtc support -i, and this is often better than using #include since you get correct line number information in errors.
What issue is there with line numbers when using dtc? Recent dtc supports #line directives from the pre-processing results, and hence reports errors in terms of the source files, just like raw dtc without cpp.
That's the issue. What does dtc v1.3 do?
v1.3 doesn't include the feature, but it also doesn't support -i either.
Unfortunately this version must be installed manually in current Linux distributions.
Well, then that gets into the problem of some .dts files choosing to use /include/ and rely on -i, but others using #include and not. I don't really think it's a good idea to propagate both versions. Picking one and using it would be far better.
I really do think we should simply require a reasonably recent dtc and be done with it.
I would be happy with that, but it can be an extra barrier to getting U-Boot building.
The Linux kernel chose to solve this by bundling the required dtc source inside the kernel source tree as a tool. This seems by far the simplest way to solve the problem for U-Boot too. If not, it's not exactly hard to:
git clone make
... given that one is already building U-Boot from source anyway.
So do we need using #include at all if we are using -i ?
Well, *.dts are moving to #include (and other cpp constructs) rather than /include/ in the copies in the Linux kernel, which I think will eventually make their way into U-Boot for consistency. Equally, if/when *.dts get separated out into a separate project from the kernel, I think we'd want the same to happen for U-Boot so that the same *.dts is used. Then, there won't be a choice.
Some device tree files use the word 'linux' which gets replaced with '1' by many version of gcc, including version 4.7. So undefine this.
Linux chose to use -undef rather than undefining specific/individual defines. It'd be best to be consistent to that .dts files are more likely to be portable between the two.
Seems a bit extreme, but OK. Are you worried that gcc defines other things without the double underscore?
IIRC there were some other issues, yes. "unix" may have been one of them. The problem was reported (and I think that fix suggested) by someone else, so I don't remember the full details, although they're in the mailing list archives I suppose.
diff --git a/dts/Makefile b/dts/Makefile
-DARCH_CPU_DTS=\"$(SRCTREE)/arch/$(ARCH)/dts/$(CONFIG_ARCH_DEVICE_TREE).dtsi\" \ -DBOARD_DTS=\"$(SRCTREE)/board/$(VENDOR)/$(BOARD)/dts/$(DEVICE_TREE).dts\" \
-I$(SRCTREE)/board/$(VENDOR)/dts -I$(SRCTREE)/arch/$(ARCH)/dts
-D__ASSEMBLY__ -I$(OBJTREE)/include -I$(SRCTREE)/include \-I$(OBJTREE)/include2 \Do we really want include or include2 (what's that?) at all? The .dts files really should be standalone, and not interact with the U-Boot headers at all.
I understood that you were wanting to make use of U-Boot defines. If you want to include include/config.h then I think you need these.
I hope I didn't want to:-) The DT should really represent the HW not anything about the way U-Boot is configured.
-include $(OBJTREE)/include/config.h+DTS_TMP := $(OBJTREE)/include/generated/$(DEVICE_TREE).dts.in
Hmm. This really isn't a generated header file. Can this instead be $(OBJTREE)/$(dir $@).$(notdir $@).dts or something like that?
I didn't say header file.
The nice thing about having everything in include/generated is that it doesn't pollute the source for in-tree builds.
Well, it's in a directory that's for generated headers; it has "/include/" in the path. I don't think we should put it somewhere that C code could accidentally #include it, irrespective of how (un-)likely that is to get passed review. Also, for in-tree builds, doesn't every single other derived file get put into the source tree? I'm not sure why this file would need to be special?
+$(DT_BIN): $(TOPDIR)/$(DTS_SRC) rc=$$( \
cat $< | $(CPP) -P $(DTS_CPPFLAGS) - | \{ { $(DTC) -R 4 -p 0x1000 -O dtb -o ${DT_BIN} - 2>&1 ; \
cat $< | $(CPP) -P $(DTS_CPPFLAGS) - > $(DTS_TMP); \{ { $(DTC_CMD) 2>&1 ; \...
if [ $$rc != 0 ]; then \echo "Source file is $(DTS_SRC)"; \echo "Compiler: $(DTC_CMD)"; \fi; \Isn't that what make V=1 is for?
It produces about 800KB of other spiel though. If the build fails it is already printing stuff out - so I find this useful.
But again, why be special? I could apply the same argument to every single other C file where I might have typo'd something.