kernel headers not properly generated on platforms with a mach- and a plat- (i.e. mach-mx5, plat-mxc etc.)

[Matt Sealey]

Okay so it's a Debian packaging problem then. To get dkms and similar
to work properly with just -headers there are a bunch of hacks (it
installs a pre-prepped kernel tree up to the point it's needed to get
that to work) and this would have to be handled.

Arnd, Thanks for the machdirs hint.

-- 
Matt Sealey <matt at genesi-usa.com>
Product Development Analyst, Genesi USA, Inc.



On Sat, Jan 29, 2011 at 3:43 AM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Fri, Jan 28, 2011 at 06:57:19PM -0600, Matt Sealey wrote:
>> Puzzling over this again, is there some deep dark reason that if I
>> create kernel headers (headers_install or headers_check) for MX51
>> processors, or anything with a mach- AND a plat-, that the
>> plat-foo/include/mach/* headers are not copied into the header tree?
>
> headers_install does not install headers for building modules.  It
> installs headers for use by userspace - specifically your libc.  These
> headers purposely do not contain any platform specifics because those
> are not part of the userspace API.  They also have various kernel
> specific information stripped out of them.
>
> They are completely unsuitable for building anything kernel-related.
>
>> As a quick example, build any external module (compat-wireless is a
>> good example) or libc against the headers alone and not the full
>> source and they will complain about asm/memory.h trying to include
>> mach/memory.h which does not exist. Doing a little hack to copy those
>> files across absolutely fixes it.
>
> asm/memory.h is not part of headers_install.
>
>> I know there is a weirdness here: the root arch/arm/Kconfig in my tree
>> includes plat-mxc/Kconfig which includes mach-mx5/Kconfig. This is how
>> the magic happens, but I can't find any magic that modifies the
>> include paths to pick includes from these directories in the first
>> place. They don't seem symlinked into the asm-arm/mach directory on a
>> kernel build.
>
> We don't use symlinks anymore when dealing with header file directories.
>
> You can only build modules against the kernel source.  Building external
> modules is documented in Documentation/kbuild/modules.txt.  This requires
> more than just the kernel headers - it requires a preconfigured kernel
> tree, which if you're using modversions, has already been built.
>