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Date: Fri, 1 Oct 2010 07:40:49 -0400
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Subject: Re: [PATCH 01/18] powerpc: Add ability to build little endian kernels
From: Josh Boyer <jwboyer@gmail.com>
To: Ian Munsie <imunsie@au1.ibm.com>
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On Fri, Oct 1, 2010 at 3:05 AM, Ian Munsie <imunsie@au1.ibm.com> wrote:
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platfo=
rms/Kconfig.cputype
> index d361f81..074ff12 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -329,3 +329,19 @@ config CHECK_CACHE_COHERENCY
> =A0 =A0 =A0 =A0bool
>
> =A0endmenu
> +
> +config ARCH_SUPPORTS_LITTLE_ENDIAN
> + =A0 =A0 =A0 bool
> +
> +config CPU_LITTLE_ENDIAN
> + =A0 =A0 =A0 bool "Build little endian kernel"
> + =A0 =A0 =A0 depends on ARCH_SUPPORTS_LITTLE_ENDIAN && EXPERIMENTAL
> + =A0 =A0 =A0 default n
> + =A0 =A0 =A0 help
> + =A0 =A0 =A0 =A0 This option selects whether a big endian or little endi=
an kernel will
> + =A0 =A0 =A0 =A0 be built.
> +
> + =A0 =A0 =A0 =A0 Note that if building a little endian kernel, CROSS_COM=
PILE must
> + =A0 =A0 =A0 =A0 point to a toolchain capable of targetting little endia=
n powerpc,
> + =A0 =A0 =A0 =A0 while the toolchain specified by CROSS32_COMPILE must b=
e capable of
> + =A0 =A0 =A0 =A0 targetting *BIG* endian PowerPC.

Have you tested this support with a userspace containing floating
point instructions?  I wonder if CONFIG_MATH_EMULATION is going to
need work at all, and if the boards with an actual FPU (440EP, 440EPx,
460EX, etc) would have issues.

josh