new way of writing defconfigs for freescale's powerpc platforms

[Lijun Pan]

> -----Original Message-----
> From: Michael Ellerman [mailto:mpe at ellerman.id.au]
> Sent: Friday, April 17, 2015 1:19 AM
> To: Wood Scott-B07421
> Cc: Pan Lijun-B44306; linuxppc-dev at ozlabs.org; Schmitt Richard-B43082
> Subject: Re: new way of writing defconfigs for freescale's powerpc platforms
> 
> On Thu, 2015-04-16 at 23:13 -0500, Scott Wood wrote:
> > On Fri, 2015-04-17 at 10:54 +1000, Michael Ellerman wrote:
> > > On Thu, 2015-04-09 at 21:52 +0000, Lijun Pan wrote:
> > > > Hi Maintainers,
> > > >
> > > > We have a proposal for writing the defconfigs for freescale's powperpc
> platforms in a new way.
> > > > Can you take a look and provide some feedback?
> > > >
> > > > You know currently we have mpc85xx_defconfig, corenet32_defconfig,
> bsc913x_defconfig, *fman*_defconfig, etc.
> > > > We are going to extract some common parts from the existing defconfigs,
> and name it, say, fsl_basic_defconfig.
> > > > Then, we could create some defconfigs targeting specific features or
> specific platforms.
> > > > Say, features specific: kvm_defconfig, fman_defconfig, etc.
> > > > Platforms specific: p1_defconfig, p2_defcongfig, p4_defconfig,
> > > > t1_defconfig, t2_defconfig, t2_defconfig, b4_defconfig, etc When
> > > > we want to make a kernel image for p1 platform, Using the following
> steps:
> > > >
> > > > make ./scripts/kconfig/merge_config.sh
> > > > arch/powerpc/configs/fsl_basic_config p1_defconfig make
> > > >
> > > > What do you think of this new approach?
> > >
> > > I don't like that the user has to manually run merge_config.sh.
> > >
> > > How does a user even know that it's an option?
> > >
> > > It also breaks scripts that auto build the kernel, which expect to be able to
> do:
> > >
> > >   $ make foo_defconfig
> > >   $ make
> > >
> > > Scripts like mine for example :)
> > >
> > >   http://kisskb.ellerman.id.au/kisskb/head/8734/
> > >
> > > What I'd be happy with is something that does merge_config under the
> > > covers. So a user still runs 'make fsl_plat_foo_defconfig', but
> > > under the covers it does a merge config.
> > >
> > > kvmconfig and tinyconfig are implemented that way already, so with a
> > > bit more work hopefully you can do that for arch configs also.
> >
> > kvmconfig and tinyconfig are still separate user-visible steps to be
> > applied after running a base defconfig.
> 
> Not as of recently:
> 
> 
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/scripts/kc
> onfig/Makefile?id=63a91033d52e64a22e571fe84924c0b7f21c280d
> 

Above patch is very generic.
With this patch, we don't even need to modify arch/powerpc/Makefile.
We can just add fragments (like smp.config, kvm_guest.config, etc) under
arch/powerpc/configs/ or
add platform independent config under kernel/configs/

example might be:
make mpc85xx_defconfig
make smp.config
make kvm_guest.config

> 
> Which pretty much does what you describe below I think.
> 
> > For breaking a platform defconfig into components, we could do
> > something like this in arch/powerpc/Makefile:
> >
> > # Can't call mergeconfig directly as it isn't defined at this point
> > define domerge
> >        @$(MAKE) -f $(srctree)/scripts/kconfig/Makefile $(1).config
> > endef
> >
> > corenet64_smp_defconfig: corenet64_basic_defconfig
> > 	$(call domerge,smp)
> > 	$(call domerge,altivec)
> > 	$(call domerge,corenet_drivers)
> > 	$(call domerge,embedded_misc) # filesystems etc
> >
> > And this in scripts/kconfig/Makefile:
> >
> > %.config:
> >        $(call mergeconfig,$*)
> >
> > One issue with this is that we'd lose the ability to use savedefconfig
> > (at least without manual manipulation of the results) to maintain the
> > defconfigs/fragments.
> 
> That's probably OK, it's only maintainers who need to do that.
> 
> cheers
>