cc'ing Ubuntu kernel team.
We use their config system today and this might be of interest to them for the future.
On Wed, Mar 9, 2011 at 4:32 AM, John Stultz john.stultz@linaro.org wrote:
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-mana...
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:
- We cannot select items from a choice block
- 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).
The Ubuntu configs do something similar. The config generator makes a 3-level config - distro, arch, board.
But this is encapsulated under the debian packaging rather than in the kernel source. That is why you probably haven't seen it yet. Look at git://git.linaro.org/ubuntu/linux-linaro-natty.git under debian.linaro/config.
Most kernel developers, however, don't really care about creating a .deb package of the kernel to test new code. They'd rather have the config available in the sources. So I agree that we should fix this problem for them. If it turns out that in fixing this problem we fix it for distros too, great!
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.
No, it doesn't. The system they use allows for unified configs. The Ubuntu kernel has unified configs across 3-4 architectures.
The problem is starting a new config for a new board/SoC. The current config system expects a full config for the board dropped into place and then let the tool split it out into distro/arch and board components. If this causes any changes to the distro/arch configs, you know you might have missed some options.
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:
- 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.
- 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.
- The Kconfig.distro file should be probably broken up into
policy topics, like networking, filesystems, peripherials, etc.
- 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.
- 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.
They do use the same config - or 'flavour' as they are referred to in the Ubuntu kernel config system.
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@secretlab.ca CC: Jason Hui jason.hui@linaro.org CC: patches@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
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