[PATCH 1/2] ARM: multi_v7_defconfig: Enable shmobile platforms

[Kukjin Kim]

Arnd Bergmann wrote:
> 
Hi,

> On Friday 29 August 2014 20:05:49 Bartlomiej Zolnierkiewicz wrote:
> > I've been looking lately into making it possible to easily go
> > from multi_v7_defconfig config to a single platform one (in my
> > case Exynos one) and removing the need to keep the latter (i.e.
> > exynos_defconfig) in the kernel tree in the long-term.
> >
Why? I don't have any idea why we should use only multi_v7_defconfig for each
hardware platform. In my understanding, multi_v7_defconfig can be used for one
kernel image can support all of the platforms but it doesn't mean it should be
used for each platform. And I think, if we cannot maintain each platform's
defconfig in mainline, it will be kept in each SoC vendor and it is not a good
way. I mean both defconfigs has each value in mainline, exynos_defconfig should
be updated though ;)

> > Because of this I've noticed that some config options for platform
> > specific hardware that are selected in multi_v7_defconfig don't
> > have proper dependencies.  This results in more complex than
> > necessary single platform configs (obtained from a multiplatform
> > config) and unnecessarily bigger resulting kernel images.
> >
> > Your patch also adds/uncovers some such config options.
> >
> > Lets first look at sizes of resulting vmlinux images for single
> > platform Exynos config before and after your patch:
> >
> >   $ size vmlinux.*
> >      text    data     bss     dec     hex filename
> >   7817317  517188  278992 8613497  836e79 vmlinux.before
> >   7978325  527012  279056 8784393  860a09 vmlinux.after
> >
> >   (=> the patch results in 170kB bigger vmlinux size)
> >
> 
> Interesting work. We don't currently have a policy for this,
> so we should first talk about whether the behavior that you
> want is desirable. The alternative would be that everybody
> who wants to build a platform-specific kernel out of
> multi_v7_defconfig has to go through the extra work of not
> only disabling the platforms but also the individual drivers
> for the other platforms.
> 
> This is a bit tricky for drivers that may be shared between
> a few platforms in multi_v7_defconfig but are meaningless
> on the others. We could solve that by having more complex
> dependencies for each of those drivers, but that is where
> maintaining those gets really messy.
> 
Agreed and it is not required.

> A related problem that I think is more significant is that
> some platforms 'select' a particular driver and when you
> disable the platform, that driver is suddenly removed from the
> defconfig for all other platforms as well. This has bitten
> us a few times in the past, and I'd really like to fix those
> cases first.

- Kukjin