Re: [Buildroot] [PATCH v2 4/4] arch: rework MMU option handling and move to "Target architecture" menu

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Yann,

Thanks for the review!

On Wed, 27 Jul 2022 10:30:20 +0200
"Yann E. MORIN" <yann.morin.1998@free.fr> wrote:

> I am not sure why you are removing a generic option in favour of two
> arch-specific options that behave exactly the same.

The motivation is explained in the commit log. Quoting it

================================================================
However, if we simply move it in arch/Config.in, it means that we
would have the following order of options:

 Target architecture
 Target architecture variant
 ABI
 MMU
 Binary format

But really, the MMU option should be right below the Target
architecture variant, and the available ABIs derived from that.
================================================================

> Why not just keep that:
> 
>     config BR2_USE_MMU
>         bool "MMU support" if BR2_ARCH_HAS_MMU_OPTIONAL
>         default y if BR2_ARCH_HAS_MMU_OPTIONAL
> 
> This still achieves what you want:
>   - arch/variants that have a mandatory MMU can directly select
>     BR2_USE_MMU as this patch does, and the prompt does not appear
>     in that case;
>   - arch/variants that have no MMU don't select BR2_USE_MMU, and
>     there is no prompt either
>   - arch/variants that have an optrional MMU select
>     BR2_ARCH_HAS_MMU_OPTIONAL, BR2_USE_MMU is default y, and there
>     is a prompt.
> 
> And then we drop one Kconfig knob (MMU_MANDATORY), and do not need to
> introduce two others (one for riscv and one for xtensa).
> 
> I.e. the case for arch-specific options is not clear to me...

See above :-)

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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