GLEP: 33
Title: Installing kernel module source additionally to/instead of building it
Version: $Revision: $
Last-Modified: $Date: $
Author:	Stefan Schweizer <genstef@gentoo.org>, John Mylchreest <johnm@gentoo.org>
Status: Draft
Type: Standards Track
Content-Type: text/x-rst
Created: 16 Nov 2004

Abstract
========

This GLEP aims at providing users with a new external kernel module build
system by optionally installing sources, or modules, or both.

Motivation
==========

Gentoo's current module ebuild system is slow and does not track the packages
to recompile. Currently we have ebuilds in portage that provide both userspace
and kernel part, for example fuse and submount. That makes compiling user tools
when users upgrade kernels additional bloat.

Rationale
=========

One way to solve the problem is to install the module sources, so that we
can track what source modules are installed, and fast recompile them after the
kernel has been recompiled.

Implementation
==============

We will install fully patched kernel module sources in
/usr/src/linux-modules/${PN}.

Patching includes:
	avoid calling depmod
	avoid touching files out of /usr/src or /lib/modules
	using a standard variable for KERNELDIR
	and support of make and make install.

When the build is run, it will honour 2 use flags (this is mostly eclass driven).
USE="binary source"
We will install only the source if -binary -source.
The basic process will be:

pkg_setup
	check kernel supports modules
	check other config options we might need

src_compile
	if installing source
		copy module src to image/usr/src/linux-modules/PN/
		populate metadatafiles (BUILD_ARAMS)
	if installing module build module in workdir
	
src_install
	if installing module doins ${MODULES}

When the ebuild installs the module source it will also echo build parameters to
a BUILD_PARAM file in the module source directory. This is used to allow us to control additional
make options after its initial install.

There is also need to create an external tool to recompile some, or all of the modules.
For example, those specified in /etc/kmod.conf. The tool basically does:

KERNELDIR="$(pwd)"
for i in /usr/src/linux-modules/*
do
	cd ${i}
	make clean
	make $(< BUILD_PARAMS)
	make install
done
depmod

Backwards Compatibility
=======================

This is an additional feature and existing behaviour will not change.

Reference Implementation
========================

Roadmap:

- create the user space tool
- create some example ebuilds
- change the kernel module eclass to support this, and if required,
  change ebuild src_* pkg_* functions to properly use eclass functionality.

References
==========

No links here
.. [#nothin] http://nothin

Copyright
=========

This document has been placed in the public domain.