Subject: [PATCH 2/9] ARM: mmp: distinguish mmp and mmp2 in Kconfig

From: [email-masked] (Arnd Bergmann)
Date: Wed, 2 May 2012 12:58:24 +0000

On Wednesday 02 May 2012, Haojian Zhuang wrote:
> On Sat, Apr 28, 2012 at 4:14 AM, Arnd Bergmann <[email-masked]> wrote:
> > On Friday 27 April 2012, Haojian Zhuang wrote:
> >> Append four CONFIG_* MACRO to distinguish boards in arch-mmp.
> >>
> >> CONFIG_MMP_LEGACY and CONFIG_MMP2_LEGACY are used to support boards
> >> without device tree.
> >>
> >> CONFIG_MMP_DT and CONFIG_MMP2_DT are used to support boards with
> >> device tree.
> >>
> >> At the same time, only one of these four macro could be selected.
> >> It's used to miss compiling all boards file together.
> >
> > Can you explain why this is done? It seems counterintuitive to
> > have the DT and non-DT support be mutually exclusive.
> >
> If I selected DT support, I needn't select those machine support one
> by one. I want to use
> mmp-dt to support all PXA168/PXA910 boards, and use mmp2-dt to support
> all mmp2 boards.
> So I use exclusive statements in Kconfig for convenience.

Everyone else who is adding DT support does it so that one can boot
the same kernel using ATAG or DT mode, to allow testing in direct
comparison for the transitional period. Further, you can currently
build a single kernel that supports all board files including DT
support, with this patch you have to build two separate kernels,
which I consider a regression.

I guess this would be ok if you plan to remove the non-DT board files
from mach-mmp soon (e.g. v3.6) and only support DT booting, providing
the same feature set as today with the board files. If you think you
need longer than that, I would prefer if you make the two options
coexist in the kernel.

	Arnd