Commit 0da6bcd9fcc0 ("scripts: dtc: Build fdtoverlay tool") enabled
building fdtoverlay, but failed to add it to .gitignore.

Also add a note to keep hostprogs in sync with .gitignore.

Fixes: 0da6bcd9fcc0 ("scripts: dtc: Build fdtoverlay tool")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>

We will start building overlays for platforms soon in the kernel and
would need fdtoverlay going forward. Lets start building it.

The fdtoverlay program applies one or more overlay dtb blobs to a base
dtb blob. The kernel build system would later use fdtoverlay to generate
the overlaid blobs based on platform specific configurations.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/4a201dea3ba11a00cab7e936dfc1140dac1a1ae3.1611904394.git.viresh.kumar@linaro.org

When building with

	$ HOST_EXTRACFLAGS=-g make

the expectation is that host tools are built with debug informations.
This however doesn't happen if the Makefile assigns a new value to the
HOST_EXTRACFLAGS instead of appending to it. So use += instead of := for
the first assignment.

Fixes: e3fd9b5384f3 ("scripts/dtc: consolidate include path options in Makefile")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Rob Herring <robh@kernel.org>

To build host programs, you need to add the program names to 'hostprogs'
to use the necessary build rule, but it is not enough to build them
because there is no dependency.

There are two types of host programs: built as the prerequisite of
another (e.g. gen_crc32table in lib/Makefile), or always built when
Kbuild visits the Makefile (e.g. genksyms in scripts/genksyms/Makefile).

The latter is typical in Makefiles under scripts/, which contains host
programs globally used during the kernel build. To build them, you need
to add them to both 'hostprogs' and 'always-y'.

This commit adds hostprogs-always-y as a shorthand.

The same applies to user programs. net/bpfilter/Makefile builds
bpfilter_umh on demand, hence always-y is unneeded. In contrast,
programs under samples/ are added to both 'userprogs' and 'always-y'
so they are always built when Kbuild visits the Makefiles.

userprogs-always-y works as a shorthand.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

Commit 067c650c456e ("dtc: Use pkg-config to locate libyaml") added
'pkg-config --libs' to link libyaml installed in a non-standard
location.

yamltree.c includes <yaml.h>, but that commit did not add the search
path for <yaml.h>. If /usr/include/yaml.h does not exist, it fails to
build. A user can explicitly pass HOSTCFLAGS to work around it, but
the policy is not consistent.

There are two ways to deal with libraries in a non-default location.

[1] Use HOSTCFLAGS and HOSTLDFLAGS for additional search paths for
    headers and libraries.
    They are documented in Documentation/kbuild/kbuild.rst

    $ make HOSTCFLAGS='-I <prefix>/include' HOSTLDFLAGS='-L <prefix>/lib'

[2] Use pkg-config

    'pkg-config --cflags' for querying the header search path
    'pkg-config --libs'   for querying the lib and its path

If we go with pkg-config, use [2] consistently. Do not mix up
[1] and [2].

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

If you run 'make dtbs_check' without installing the libyaml package,
the error message "dtc needs libyaml ..." is shown.

This should be checked also for 'make dt_binding_check' because dtc
needs to validate *.example.dts extracted from *.yaml files.

It is missing since commit 4f0e3a57d6eb ("kbuild: Add support for DT
binding schema checks"), but this fix-up is applicable only after commit
e10c4321dc1e ("kbuild: allow to run dt_binding_check and dtbs_check
in a single command").

I gave the Fixes tag to the latter in case somebody is interested in
back-porting this.

Fixes: e10c4321dc1e ("kbuild: allow to run dt_binding_check and dtbs_check in a single command")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

The dt_binding_check target is located outside of the
'ifneq ($(dtstree),) ... endif' block.

So, you can run 'make dt_binding_check' on any architecture.
This makes a perfect sense because the dt-schema is arch-agnostic.

The only one problem I see is that scripts/dtc/dtc is not always built.
For example, ARCH=x86 defconfig does not define CONFIG_DTC. Kbuild
descends into scripts/dtc/ with doing nothing. Then, it fails to build
*.example.dt.yaml files.

Let's build scripts/dtc/dtc forcibly when running dt_binding_check.

The dt-schema does not depend on any CONFIG option either, so you
should be able to run dt_binding_check without the .config file.

Going forward, you can directly run 'make dt_binding_check' in a
pristine source tree.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>

In old days, the "host-progs" syntax was used for specifying host
programs. It was renamed to the current "hostprogs-y" in 2004.

It is typically useful in scripts/Makefile because it allows Kbuild to
selectively compile host programs based on the kernel configuration.

This commit renames like follows:

  always       ->  always-y
  hostprogs-y  ->  hostprogs

So, scripts/Makefile will look like this:

  always-$(CONFIG_BUILD_BIN2C) += ...
  always-$(CONFIG_KALLSYMS)    += ...
      ...
  hostprogs := $(always-y) $(always-m)

I think this makes more sense because a host program is always a host
program, irrespective of the kernel configuration. We want to specify
which ones to compile by CONFIG options, so always-y will be handier.

The "always", "hostprogs-y", "hostprogs-m" will be kept for backward
compatibility for a while.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Using Makefile's wildcard with absolute path to detect
the presence of libyaml results in false-positive
detection when cross-compiling e.g. in yocto environment.
The latter results in build error:
| scripts/dtc/yamltree.o: In function `yaml_propval_int':
| yamltree.c: undefined reference to `yaml_sequence_start_event_initialize'
| yamltree.c: undefined reference to `yaml_emitter_emit'
| yamltree.c: undefined reference to `yaml_scalar_event_initialize'
...
Use pkg-config to locate libyaml to address this scenario.

Signed-off-by: Pavel Modilaynen <pavel.modilaynen@axis.com>
[robh: silence stderr]
Signed-off-by: Rob Herring <robh@kernel.org>

Currently, the Kbuild core manipulates header search paths in a crazy
way [1].

To fix this mess, I want all Makefiles to add explicit $(srctree)/ to
the search paths in the srctree. Some Makefiles are already written in
that way, but not all. The goal of this work is to make the notation
consistent, and finally get rid of the gross hacks.

Having whitespaces after -I does not matter since commit 48f6e3cf5bc6
("kbuild: do not drop -I without parameter").

[1]: https://patchwork.kernel.org/patch/9632347/

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>