[PATCH 00/12][RFC] Intial Kconfig Fragment Demo

[John Stultz]

This patch set provides enough to demo how the Kconfig fragment
based defconfigs could be used to simplify both generating and
managing the configs used to build Linaro kernels.

This is for the kernel config managment tool and dependent bluprints:
https://blueprints.launchpad.net/linux-linaro/+spec/other-kernel-config-management-tool


The basic idea is to use a Kconfig fragment to generate the 
per-board defconfigs. The Kconfig fragments contain a meta-option
that defaults to yes, which then selects the needed config values
to enable a system.

This has been proposed by others, and we're using Stephen
Rothwell's initial patch to start things off.

Once we have the infrasturcture to use Kconfig fragments for
defconfigs we had to overcome some limitations:
1) We cannot select items from a choice block
2) We need a way to select for values and modules.

Limitation #1 is resolved by a patch to the kbuild system I 
made.

Limitation #2 is unsolved, but Jason Hui found a workaround that
is sufficient. Basically we can just redefine the default with a 
short declaration: 
	config VAL
		default 256
or 
	config VAL
		default m


With these two solutions, I went forward generating basic Kconfig
fragments for omap3, imx51 and vexpress. 

Getting per-board defconfigs is only of limited value, because 
we also want to be able to have a common policy settings for
Linaro kernels. Many distros run into this problem, and use 
.config fragments which are then assembled at package build 
time. 

My solution is to have a Kconfig.distro file, which is patched
with Distro specific policy config, such as which filesystems
should be enabled, networking policy, debug options, or periphrial 
driver modules that should be enabled. Basically anything that
isn't hardware specific (by that I mean, part of the architecture
or wired on the board).

>From there, I add in as much of the generic Linaro config policy
as I could, utilizing the config files that were used to build
the omap3, imx51 and vexpress hardware packs.

Since the Linaro config polciy is not unified at this point
(in other words, each board has totally different set of generic
policy options configured). I added the per target differences
into the board kconfig fragments.

Ideally we can review and settle down on specific linaro config
policy and this generic per-board stuff can go away.

These are initial and rough patches, but are the result of lots
of painful manual labor to match the Linaro .configs as closely
as possible.

There are a few remaining issues, but these can probably be
worked around:
1) Omap has a strange tristate choice option for the usb gadget
options. So you can only pick one, or you can pick multiple items
as modules. My choice selection patch doesn't yet address this.
I need to see how common this style of choice is and see if we
can either just make it a non-choice options block or if other
fixes are needed.

2) Not having a module selction is a little painful, as the 
module "default m" entries are numerous and annoyingly separate
from the meta-config selects.

3) The Kconfig.distro file should be probably broken up into 
policy topics, like networking, filesystems, peripherials, etc.

4) The current board Kconfig fragments are named slightly
differently from the standard defconfigs to allow testing
with both. That will need to be fixed, and the old defconfigs
removed prior to submitting.

5) The igep, overo, and panda configs all use the same omap3
config according to the hwpacks. I'm not sure I believe that,
but went along with it to get this out the door.


Many thanks to Jason for his help figuring out an approach here.

Feedback and thoughts would be greatly appreciated.

thanks
-john


CC: Grant Likely <grant.likely at secretlab.ca>
CC: Jason Hui <jason.hui at linaro.org>
CC: patches at linaro.org


John Stultz (11):
  kbuild: Allow configs from choice blocks to be selected.
  kbuild: Use kconfig defaults as defconfig starting point
  kbuild: Avoid kconfig fragment defconfigs from having odd config
    order
  Add blank Kconfig.distro fragment file
  Initial omap3 Kconfig fragment
  Initial imx51 defconfig fragment
  Add initial vexpress defconfig fragment
  Add Linaro config policy to Kconfig.distro
  omap3 kconfig fragment changes to align with linaro build
  Update imx51 to better match linaro configs
  Update vexpress to be closer to linaro config

Stephen Rothwell (1):
  kbuild: Enable building defconfigs from Kconfig files

 Kconfig.distro                 | 1754 +++++++++++++++++++++++++++++
 arch/arm/configs/Kconfig.imx51 |  503 +++++++++
 arch/arm/configs/Kconfig.omap3 | 2430 ++++++++++++++++++++++++++++++++++++++++
 arch/arm/configs/Kconfig.vexp  |  234 ++++
 scripts/kconfig/Makefile       |   16 +-
 scripts/kconfig/symbol.c       |   15 +-
 6 files changed, 4949 insertions(+), 3 deletions(-)
 create mode 100644 Kconfig.distro
 create mode 100644 arch/arm/configs/Kconfig.imx51
 create mode 100644 arch/arm/configs/Kconfig.omap3
 create mode 100644 arch/arm/configs/Kconfig.vexp

-- 
1.7.3.2.146.gca209