[ale] cross compiling

[Boris Borisov]

thank you for detailed answer ! Could not touch computer all afternoon
so I'm checking now. Today manually add line before 79. KERNDIR :=
/user/linux-2.6.24.3 dirty way but worked. so far got driver but for
x86. In the morning will try to pass parameters to compiler ARCH=mips
and CROSS_COMPILE=mips-linux- and should work. Now is too late can put
my thoughts together :)

Thanks again

On 5/5/14, Ed Cashin <ecashin at noserose.net> wrote:
> Responses will interleave with selected quotes below.
>
> On Mon, May 5, 2014 at 11:00 AM, Boris Borisov <bugyatl at gmail.com> wrote:
>> I'm trying to get my way around cross-compiling. I have host Debian 7.5
>> and
>> the toolchain for mips. I'm working with patched 2.6.24.3 kernel because
>> that is what runs on my device. So far I got how to compile the kernel
>> for
>> mips.
>
> Congratulations.  It isn't always easy to build old kernels.  I used
> to use VMs running old versions of RHEL to build old kernels.  It also
> isn't always easy to cross compile!
>
>> My question is how you are compiling module that is not in kernel tree.
>
> I have some experience with that.  I checked out the rt73 sources from
> sourceforge.
>
> ...
>> Since the module package has its own Makefile: do you make changes in
>> this
>> Makefile or you start make with extra parameters?
>
> Maybe it's helpful to break down how the parts of the build relate.
> Sorry if you know all this, but the Module/Makefile inside rt73 looks
> for the kernel sources via the expected "build" symlink:
>
>     79  ifdef KERNDIR
>     80   KERNEL_SOURCES := $(KERNDIR)
>     81  else
>     82   KERNEL_SOURCES := /lib/modules/$(shell uname -r)/build
>     83  endif
>
> ... so you can do 'make KERNDIR=/path/to/my/sources' ... to specify your
> own.
>
> It uses the KERNEL_SOURCES to build parameters for the build command:
>
>    115  KBUILD_PARAMS := -C $(KERNEL_SOURCES) SUBDIRS=$(CURDIR)
> $(KERNEL_OUTPUT)
>
> Notice the "-C" option.  That's going to cause make to change
> directories to the kernel sources and to use the Makefile there.  So
> this is a recursive make, where it starts out in the rt73 sources but
> quickly changes to the kernel sources.
>
> When it's (the child) make running on the Makefile in the kernel
> sources, it's being told to build the modules in the subdirectories
> $(SUBDIRS), which is set to be rt73's Module/ subdirectory.
>
> Back when rt73 invoked this child make, it passed on the EXTRA_CFLAGS:
>
>    127  module:
>    128          @$(MAKE) $(KBUILD_PARAMS)
> 'EXTRA_CFLAGS=$(EXTRA_CFLAGS)' modules; \
>    129          $(MODULE_CHECK)
>
> ... and that suggests that you can supply EXTRA_CFLAGS from your
> invocation inside rt73's Module/ subdirectory.  You can also edit
> Module/Makefile if you like.
>
> With that example, you can probably think of ways to get other
> variables to show up in the kernel build as well.
>
> --
>   Ed Cashin <ecashin at noserose.net>
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