Updating the upstream source
============================

1) You can use either:
   a) a git repository of the kernel source
   b) a kernel tarball from kernel.org (e.g. linux-2.6.25.tar.bz2)
      and, optionally, a patch (e.g. patch-2.6.26-rc3.bz2).

2) Run ./debian/bin/genorig.py <repository>
   or  ./debian/bin/genorig.py <tarball> [patch]
   This will produce ../orig/linux-2.6_<version>.orig.tar.gz
   (e.g. linux-2.6_2.6.26~rc3.orig.tar.gz).

   (genorig.py requires the python and unifdef packages to be
    installed)

3) Unpack linux-2.6-<version>.orig.tar.gz, cd into the new directory,
   and do a 'svn export' to get the debian/ subdirectory.
   Alternatively unpack using "make -f debian/rules orig".

   (the orig target of the Makefiles requires rsync)

Applying patches to the Debian kernel tree
==========================================

The Debian kernel packaging uses a custom patching system:

Patches are stored below debian/patches, loosely sorted in bugfix/,
features/ and debian/. Patches are in the standard kernel patch
format.

The order and the selection of patches which are applied during build
time are specified in the series/ subdirectory. For each revision
there may be up to one file named REVISION specifying the patches
applied for the standard revision and one file named REVISION-extra
for addon flavours. If, e.g. the patches are specified for 2.6.26-12, 
the patch order file is called debian/patches/series/12 for the
standard kernel images and debian/patches/series/12-extra for the
addon flavours.

Let's look at the actual series file for 2.6.26-12:

+ bugfix/all/net-unix-gc-fix-soft-lockups-oom-issues.patch
+ bugfix/all/inotify-watch-removal-umount-races.patch
+ bugfix/all/atm-duplicate-listen-on-socket-corrupts-the-vcc-table.patch
+ bugfix/all/ata-pata_marvell-vs-ahci.patch
+ features/sparc/video-sunxvr500-intergraph.patch

The patches to be applied are specified relative to debian/patches.
"+" indicates that the patch should be added, "-" can be used to
drop a patch in later patch series (e.g. if the patch turned out to
be faulty). The series files may be arbitrarily documented with 
comments starting with "#".

Let's now have a look at the series file for the addon kernel flavours
of 2.6.26-12:

+ features/all/xen/dom0-fix-processor-throttling-when-pr-id-is-minus-1.patch featureset=xen

The same syntax applies for specifing the patches, but an additional
argument is needed which specifies the featureset the patch applies to.


If you want to generate a source tree with all patches applied, run
make -f debian/rules source-all

The resulting source can be found below debian/build.

Kernel config files
===================
Configuration files are constructed dynamically from a number of config
files, as listed in debian/config/<arch>/defines.

Control file
============
The master control file debian/control must be generated before
the package is uploaded. debian/rules contains the debian/control 
target, which generates the control file by invoking the 
debian/bin/gencontrol.py script, which combines the templates from
the templates directory and architecture-specific defines file to
produce the debian/control file. Note that this target is intentionally
made to fail with a non-zero exit code to make sure that it is never
run during an automatic build. The following variables are substituted
into the templates:

@version@      Upstream kernel version, for example 2.6.11.
@major@        The major version, for example 2.6
@arch@         The Debian arch name, such as powerpc or i386.
@flavour@      The build flavour, such as 686 or k7-smp.
@class@        The CPU/architecture class; displayed in synopsis.  It should
               be fairly short, as the synopsis is supposed to be <80 chars.
               It should be in the form "foo class", and will show up in the
	       description as "foo class machines".
@longclass@    The CPU/architecture class; displayed in the extended
               description.  The same rules apply as in @class@.  If
	       this is unset, it will default to @class@.
@desc@         (Potentially) multi-line verbiage that's appended to
               -image descriptions.
@abiname@      Current abiname, a single digit.

Normally, the arch-specific contents should be controlled by
adjusting the corresponding defines file.

TODO:
- Patches applied to the upstream source
- How to define a flavour
- More detail on generation of debian/control and configs