Re: [PATCH v3] kbuild: Add support for DT binding schema checks

[Rob Herring]

On Mon, Dec 10, 2018 at 10:39 PM Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
>
> Hi Rob,
>
> On Tue, Dec 11, 2018 at 5:50 AM Rob Herring <robh@xxxxxxxxxx> wrote:
> >
> > This adds the build infrastructure for checking DT binding schema
> > documents and validating dts files using the binding schema.
> >
> > Check DT binding schema documents:
> > make dt_binding_check
> >
> > Build dts files and check using DT binding schema:
> > make dtbs_check
> >
> > Optionally, DT_SCHEMA_FILES can passed in with a schema file(s) to use
>
>
> Perhaps, "can be passed" ?

Yes.

[...]

> > +quiet_cmd_chk_binding = CHKDT   $<
>
>
> In convention, the short log displays the target name
> instead of the prerequisite.

Yes, but here there is no target. We're just running a check on the source.


> If O=foo/bar is given, $< shows the full path,
> then log will look like follows:
>
>
>   CHKDT   /home/masahiro/ref/linux-devicetree/Documentation/devicetree/bindings/arm/calxeda.yaml
>   DTC     Documentation/devicetree/bindings/arm/calxeda.example.dtb
>   CHKDT   /home/masahiro/ref/linux-devicetree/Documentation/devicetree/bindings/arm/qcom.yaml
>   DTC     Documentation/devicetree/bindings/arm/qcom.example.dtb
>   CHKDT   /home/masahiro/ref/linux-devicetree/Documentation/devicetree/bindings/arm/xilinx.yaml
>   DTC     Documentation/devicetree/bindings/arm/xilinx.example.dtb
>   CHKDT   /home/masahiro/ref/linux-devicetree/Documentation/devicetree/bindings/arm/ti/nspire.yaml
>   DTC     Documentation/devicetree/bindings/arm/ti/nspire.example.dtb
>   CHKDT   /home/masahiro/ref/linux-devicetree/Documentation/devicetree/bindings/arm/ti/ti,davinci.yaml
>   DTC     Documentation/devicetree/bindings/arm/ti/ti,davinci.example.dtb
>   CHKDT   /home/masahiro/ref/linux-devicetree/Documentation/devicetree/bindings/arm/altera.yaml
>
> You might think it is ugly.

I've changed it to this:

quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)

[...]

> > +$(obj)/%.example.dts: $(src)/%.yaml FORCE
> > +       $(call if_changed,chk_binding)
> > +
> > +DT_TMP_SCHEMA := .schema.yaml.tmp
>
>
> BTW, why does this file start with a period?
> What is the meaning of '.tmp' extension?

Nothing really. Just named it something so it gets cleaned and ignored by git.

> > +extra-y += $(DT_TMP_SCHEMA)
> > +
> > +quiet_cmd_mk_schema = SCHEMA  $@
> > +      cmd_mk_schema = mkdir -p $(obj); \
> > +                      rm -f $@; \
> > +                      $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(filter-out FORCE, $^)
>
>
> "mkdir -p $(obj)" is redundant.
>
>
> Why is 'rm -f $@' necessary ?
> Can't dt-mk-schema overwrite the output file?

It is for error case when the output file is not generated. I can
handle this within dt-mk-schema instead.

> > +DT_DOCS = $(shell cd $(srctree)/$(src) && find * -name '*.yaml')
> > +DT_SCHEMA_FILES ?= $(addprefix $(src)/,$(DT_DOCS))
> > +
> > +extra-y += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
> > +extra-y += $(patsubst $(src)/%.yaml,%.example.dtb, $(DT_SCHEMA_FILES))
>
>
>
> I assume you intentionally did not do like this:
>
> extra-y += $(patsubst %.yaml,%.example.dtb, $(DT_DOCS))
>
> From the commit description, DT_SCHEMA_FILES might be overridden by a user.
> So, I think this is OK.
>
>
>
>
> > +$(obj)/$(DT_TMP_SCHEMA): | $(addprefix $(obj)/,$(patsubst $(src)/%.yaml,%.example.dtb, $(DT_SCHEMA_FILES)))
>
> I do not understand this line.
> Why is it necessary?
>
> *.example.dtb files are generated anyway
> since they are listed in extra-y.

It is enforcing the ordering. Without it, the binding checks and
building .schema.yaml.tmp happen in parallel because both only have
the source files as dependencies. The '|' keeps the dependencies out
of the dependency list($^).

[...]

> > +cmd_dtc_yaml_chk = \
> > +       if ! echo "/dts-v1/; /{};" | $(DTC) -I dts -O yaml > /dev/null ; then \
> > +               echo "*"; \
> > +               echo "* dtc needs libyaml for DT schema validation support."; \
> > +               echo "* Install the necessary libyaml development package from your distro."; \
> > +               echo "*"; \
> > +               false; \
> > +       fi; \
> > +       touch $@
> > +
> > +$(objtree)/scripts/dtc/.dtc-yaml-chk.tmp: $(DTC) FORCE
> > +       $(call if_changed,dtc_yaml_chk)
>
>
> Hmm, this is kind of ugly.
>
> I'd rather check this in scripts/dtc/Makefile
>
>
>
> How about something like below?

Looks good.

>  ifeq ($(wildcard /usr/include/yaml.h),)
> +ifeq ($(CHECK_DTBS),1)

I'm going to change this to "ifneq ($CHECK_DTBS),)" in case we start
supporting more than 1 value such as warning levels.

> +$(error dtc needs libyaml for DT schema validation support. \
> +        Install the necessary libyaml development package.)
> +endif
>  HOST_EXTRACFLAGS += -DNO_YAML
>  else
>  dtc-objs       += yamltree.o
>
>
>
>
>
> One drawback of this approach is,
> this is not checked if you are using out-of-tree DTC.
> Probably, Rob is the only person that overrides DTC.

Sadly, that's probably true.

Thanks for your thorough review.

Rob