[Buildroot] [PATCH v2 3/8] grub2: use grub2-tools as a host package

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello,

I'm finally reviewing this patch series. Sorry for the time it has
taken, especially since I believe it is a very useful topic. I have a
few questions below.

On Wed, 26 Apr 2017 23:39:48 +0200, Erico Nunes wrote:

> diff --git a/boot/grub2/grub2.mk b/boot/grub2/grub2.mk
> index 171829d..f0bd2ee 100644
> --- a/boot/grub2/grub2.mk
> +++ b/boot/grub2/grub2.mk
> @@ -9,7 +9,9 @@ GRUB2_SITE = http://ftp.gnu.org/gnu/grub
>  GRUB2_SOURCE = grub-$(GRUB2_VERSION).tar.xz
>  GRUB2_LICENSE = GPL-3.0+
>  GRUB2_LICENSE_FILES = COPYING
> -GRUB2_DEPENDENCIES = host-bison host-flex
> +GRUB2_DEPENDENCIES = host-bison host-flex host-grub2-tools

Do we still need to depend on host-bison and host-flex, now that the
tools are built by as part of host-grub2-tools ?

Also, what in boot/grub2/grub2.mk ensures that the tools are *not*
built ?

> +GRUB2_INSTALL_TARGET = NO

Grub really doesn't install anything to the target ? I thought it
installed some modules in /usr/lib/grub2 or something like that, that
grub2 could load dynamically at runtime. Did I miss something?

>  # Grub2 is kind of special: it considers CC, LD and so on to be the
>  # tools to build the native tools (i.e to be executed on the build
>  # machine), and uses TARGET_CC, TARGET_CFLAGS, TARGET_CPPFLAGS,
> -# TARGET_LDFLAGS to build the bootloader itself. However, to add to
> -# the confusion, it also uses NM, OBJCOPY and STRIP to build the
> -# bootloader itself; none of these are used to build the native
> -# tools.
> +# TARGET_LDFLAGS to build the bootloader itself.

It is not clear to me what is happening now: you no longer pass
HOST_CONFIGURE_OPTS in GRUB2_CONF_ENV, but we continue to pass
TARGET_CC/TARGET_CFLAGS/TARGET_CPPFLAGS, etc.

So at the very least, the comment needs to be updated.

>  #
>  # NOTE: TARGET_STRIP is overridden by BR2_STRIP_none, so always
>  # use the cross compile variant to ensure grub2 builds
>  
>  GRUB2_CONF_ENV = \
> -	$(HOST_CONFIGURE_OPTS) \
> -	CPP="$(HOSTCC) -E" \
> +	CPP="$(TARGET_CC) -E" \
>  	TARGET_CC="$(TARGET_CC)" \
>  	TARGET_CFLAGS="$(TARGET_CFLAGS)" \
>  	TARGET_CPPFLAGS="$(TARGET_CPPFLAGS)" \
>  	TARGET_LDFLAGS="$(TARGET_LDFLAGS)" \
> -	NM="$(TARGET_NM)" \
> -	OBJCOPY="$(TARGET_OBJCOPY)" \
> -	STRIP="$(TARGET_CROSS)strip"
> +	TARGET_NM="$(TARGET_NM)" \
> +	TARGET_OBJCOPY="$(TARGET_OBJCOPY)" \
> +	TARGET_STRIP="$(TARGET_CROSS)strip"

This is the part that confuses me.

> diff --git a/package/grub2-tools/grub2-tools.mk b/package/grub2-tools/grub2-tools.mk
> index 8bf1a31..f98f4aa 100644
> --- a/package/grub2-tools/grub2-tools.mk
> +++ b/package/grub2-tools/grub2-tools.mk
> @@ -10,6 +10,10 @@ GRUB2_TOOLS_SOURCE = grub-$(GRUB2_VERSION).tar.xz
>  GRUB2_TOOLS_LICENSE = GPLv3+
>  GRUB2_TOOLS_LICENSE_FILES = COPYING
>  GRUB2_TOOLS_DEPENDENCIES = host-bison host-flex
> +HOST_GRUB2_TOOLS_DEPENDENCIES = host-bison host-flex
> +
> +HOST_GRUB2_TOOLS_CONF_ENV = \
> +	CPP="$(HOSTCC) -E"
>  
>  GRUB2_TOOLS_CONF_ENV = \
>  	CPP="$(TARGET_CC) -E" \
> @@ -29,4 +33,7 @@ GRUB2_TOOLS_CONF_OPTS = \
>  	--enable-libzfs=no \
>  	--disable-werror
>  
> +HOST_GRUB2_TOOLS_CONF_OPTS = $(GRUB2_TOOLS_CONF_OPTS)
> +
>  $(eval $(autotools-package))
> +$(eval $(host-autotools-package))

Perhaps adding a host variant for the grub2-tools package could have
been a separate patch. But that's not a big deal, the above
questions/comments are much more important.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com