Cross compile rules update

[Loïc Minier]

On Wed, Sep 29, 2010, Tim Gardner wrote:
> +ifneq ($(DEB_BUILD_GNU_TYPE),$(DEB_HOST_GNU_TYPE))
> +	cross_compile = CROSS_COMPILE=$(DEB_HOST_GNU_TYPE)-
> +endif
[...]
> +ifneq ($(cross_compile),)
> +	kmake += $(cross_compile)
> +endif

 This means you don't support CROSS_COMPILE in the environment anymore;
 this is entirely correct for Debian style cross-builds, but it might
 disappoint people who use the CS toolchains: these use a different
 prefix, arm-none-linux-gnueabi-, or even arm-none-eabi-.  In the Debian
 cross scheme, this is not supposed to be supported, but nevertheless
 you could try supporting it by doing:
    ifneq ($(DEB_BUILD_GNU_TYPE),$(DEB_HOST_GNU_TYPE))
            CROSS_COMPILE ?= $(DEB_HOST_GNU_TYPE)-
    endif
    ifneq ($(CROSS_COMPILE),)
            kmake += CROSS_COMPILE=$(CROSS_COMPILE)
    endif

> +ifneq ($(cross_compile),)
> +	#
> +	# Can't build the tools 'cause the make wants cross libraries and such.
> +	#
> +	do_tools=false
> +endif

 So that's an opinionated decision on what you cross-compile.  In
 theory, these tools would cross-compile file, it's just that you lack
 some pre-dependencies: cross-built versions of libdw and libelf.

 I think we should aim at having cross-built packages as close as
 possible to natively built packages, so I would suggest not setting
 do_tools=false by default.  However, I recognize that kernel developers
 mostly cross-build as a time saver, and it's cumbersome to have to
 cross-build libdw and libelf before cross-building the kernel (or to
 import the native versions in the cross-build location).
   Perhaps it would make more sense to keep "disable tools" as an
 orthogonal option for people who only care to cross-compile the actual
 kernel, and not the tools?
   Developers could disable tools in DEB_BUILD_OPTIONS or when calling
 rules; e.g.:
    DEB_BUILD_OPTIONS=notools dpkg-buildpackage -aarmel
 or:
    DEB_BUILD_OPTIONS="do_tools=false"

 or when calling rules directly:
    debian/rules arch=armel do_tools=false

-- 
Loïc Minier