[Buildroot] [PATCH 01/11 v2] package-infra: add helper to build kernel modules

[Arnout Vandecappelle <arnout@mind.be>]

On 06/10/15 21:22, Yann E. MORIN wrote:
> The Linux kernel offers a nice and easy-to-use infra to build
> out-of-tree kernel modules.
> 
> Currently, we have quite a few packages that build kernel modules, and
> most duplicate (or rewrite) the same code over-and-over again.
> 
> Introduce a new infrastructure that provides helpers to build kernel
> modules, so packages do not have to duplicate/rewrite that.
> 
> The infrastructure, unlike any other package infra, is not standalone.
> It needs another package infra to be used. This is so that packages that
> provide both userland and kernel modules can be built easily. So, this
> infra only defines post-build and post-install hooks, that will build
> the kernel modules after the rest of the package.
> 
> Also, no host version is provided, since it does not make sense to build
> kernel modules for the host.
> 
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: Baruch Siach <baruch@tkos.co.il>
> Cc: Arnout Vandecappelle <arnout@mind.be>

 Just some comments about the comments, and an optional remark, so after fixing
those you can add my

Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

[snip]
> diff --git a/package/pkg-kernel-module.mk b/package/pkg-kernel-module.mk
> new file mode 100644
> index 0000000..608c9e6
> --- /dev/null
> +++ b/package/pkg-kernel-module.mk
> @@ -0,0 +1,89 @@
> +################################################################################
> +# kernel module infrastructure for building Linux kernel modules
> +#
> +# This file implements an infrastructure that eases development of package
> +# .mk files for out-of-tree Linux kernel modules. It should be used for all
> +# packages that build a Linux kernel module using the kernel's out-of-tree
> +# buildsystem, unless they use a complex custom build-system.

 buildsystem, build-system. What about consistently choosing "build system"? :-)

> +#
> +# In terms of implementation, this infrastructure relies on another package
> +# infrastructure, and only defines post-build and post-install hooks, so that
> +# packages can both build user-space (with any of the other *-package infra)
> +# and/or build kernel modules.

# The kernel-module infrastructure requires the packages that use it to also
# include another package infrastructure. kernel-module only defines post-build
# and post-install hooks. This allows the package to build both kernel modules
# and/or user-space components (with any of the other *-package infra).

> +#
> +# As such, it is to be used in conjunction with another *-package infra,
> +# like so:
> +#
> +#   $(eval $(kernel-module))
> +#   $(eval $(generic-package))
> +#
> +# Note: if the caller needs access to the kernel modules (either after they
> +# are built or after they are installed), it will have to define its own
> +# post-build/install hooks after calling kernel-module, but before calling

 after -> *after*

> +# the other *-package infra, like so:
> +#
> +#   $(eval $(kernel-module))
> +#   define FOO_MOD_TWEAK
> +#   	# do something
> +#   endef
> +#   FOO_POST_BUILD_HOOKS += FOO_MOD_TWEAK
> +#   $(eval $(generic-package))
> +#
> +# Note: this infra does not check that the kernel is enabled; it is expected
> +# to be enforced at the Kconfig level with proper 'depends on'.
> +################################################################################
> +
> +################################################################################
> +# inner-kernel-module -- generates the make targets needed to support building
> +# a kernel module
> +#
> +#  argument 1 is the lowercase package name

 Is there any reason to keep this, since it's not used?

> +#  argument 2 is the uppercase package name
> +################################################################################
> +
> +define inner-kernel-module
> +
> +# The kernel must be built first.
> +$(2)_DEPENDENCIES += linux
> +
> +# This is only defined in some infrastructures (e.g. autotools, cmake), but
> +# not in others (generic). So define it if not already defined.
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                              So define it here as well.


 Regards,
 Arnout

> +$(2)_MAKE ?= $$(MAKE)
> +
> +# If not specified, consider the source of the kernel module to be at
> +# the root of the package.
> +$(2)_MODULE_SUBDIRS ?= .
> +
> +# Build the kernel module(s)
> +define $(2)_KERNEL_MODULES_BUILD
> +	@$$(call MESSAGE,"Building kernel module(s)")
> +	$$(foreach d,$$($(2)_MODULE_SUBDIRS), \
> +		$$(LINUX_MAKE_ENV) $$($$(PKG)_MAKE) \
> +			-C $$(LINUX_DIR) \
> +			$$(LINUX_MAKE_FLAGS) \
> +			$$($(2)_MODULE_MAKE_OPTS) \
> +			M=$$(@D)/$$(d) \
> +			modules$$(sep))
> +endef
> +$(2)_POST_BUILD_HOOKS += $(2)_KERNEL_MODULES_BUILD
> +
> +# Install the kernel module(s)
> +define $(2)_KERNEL_MODULES_INSTALL
> +	@$$(call MESSAGE,"Installing kernel module(s)")
> +	$$(foreach d,$$($(2)_MODULE_SUBDIRS), \
> +		$$(LINUX_MAKE_ENV) $$($$(PKG)_MAKE) \
> +			-C $$(LINUX_DIR) \
> +			$$(LINUX_MAKE_FLAGS) \
> +			$$($(2)_MODULE_MAKE_OPTS) \
> +			M=$$(@D)/$$(d) \
> +			modules_install$$(sep))
> +endef
> +$(2)_POST_INSTALL_TARGET_HOOKS += $(2)_KERNEL_MODULES_INSTALL
> +
> +endef
> +
> +################################################################################
> +# kernel-module -- the target generator macro for kernel module packages
> +################################################################################
> +
> +kernel-module = $(call inner-kernel-module,$(pkgname),$(call UPPERCASE,$(pkgname)))
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F