[PATCH v2] ARM: initial multiplatform support

On 09/03/2012 11:34 AM, Arnd Bergmann wrote:

On Friday 31 August 2012, Rob Herring wrote:

quoted

[Rob Herring]: Rebased to not be dependent on the mass mach header rename.
As a result, omap2plus, imx, mxs and ux500 are not converted. Highbank,
picoxcell, mvebu, socfpga, and vexpress are converted.

v2: This version avoids the kconfig symbol name changes and simply moves
multi-platform enabled platform kconfig option out of the choice option
and into the platform's mach directory. A separate series fixes DEBUG_LL
for multi-platform.

This looks like a nice start to play with multiplatform, and I guess it
would be nice to merge it for v3.7.

quoted

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -254,27 +254,9 @@ config MMU
 #
 choice
        prompt "ARM system type"
+       depends on !ARCH_MULTIPLATFORM
        default ARCH_VERSATILE

Why did you move ARCH_MULTIPLATFORM out of the "choice" statement?
If we leave it in there, and make it the default, then we don't
even have to change the defconfigs any more (except the versatile
one, which is no longer the default), which I think is quite clever
and helps git-bisecting across this commit.

We don't have to change and of the defconfigs or .config in this patch.

Bisecting the converted platforms is a problem I guess. It can be worked
around by setting ARCH_MULTIPLATFORM before configuring. I'm not
convinced fixing it is worth the complexity added to kconfig.

I also still think that we should allow platforms to be part of
both multi-platform and single-platform builds, for cases it helps
with.

For instance, we could enable one platform to be used in
multiplatform kernels with the subset of its board files and
device drivers that are possible, while leaving board files
that cannot work with sparse-irq and drivers that rely on
platform specific headers as "depends on !ARCH_MULTIPLATFORM".

Individual platforms can still do that. I just happened to convert all
platforms which have no need to be in both. While you can do that, I
don't think we should encourage it. I don't think we want to see
platforms partially converted to common clk or sparse irq. The latter is
certainly not hard to do.

Rob