[Buildroot] [PATCH 2/6] boot/uboot: support building U-Boot with Python 3.x

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2020-05-03 15:12 +0200, Thomas Petazzoni spake thusly:
> On Sun, 3 May 2020 10:02:31 +0200
> "Yann E. MORIN" <yann.morin.1998@free.fr> wrote:
> > > +if BR2_TARGET_UBOOT_NEEDS_PYTHON
> > > +
> > > +choice
> > > +	prompt "Python version"
> > > +	default BR2_TARGET_UBOOT_NEEDS_PYTHON2
> > > +
> > > +config BR2_TARGET_UBOOT_NEEDS_PYTHON2
> > > +	bool "python 2.x"
> > > +	help
> > > +	  Select this option if U-Boot needs a host Python 2.x
> > > +	  interpreter. This is the case for some U-Boot
> > > +	  configurations, prior to U-Boot 2020.01.
> > > +
> > > +config BR2_TARGET_UBOOT_NEEDS_PYTHON3
> > > +	bool "python 3.x"
> > > +	help
> > > +	  Select this option if U-Boot needs a host Python 3.x
> > > +	  interpreter. This is the case for some U-Boot
> > > +	  configurations, after U-Boot 2020.01.
> > > +
> > > +endchoice  
> > 
> > I don't like it much that construct, where a boolean hides a choice.
> > Instead, we can siumply use a choice (options names abbreviated as I'm
> > lazy to type them full):
[--SNIP--]
> If I use depends on like you suggest, we break backward compatibility.
> Indeed, an existing configuration with

Right, so I like backward compatibility, but I also do not like the
bool-hides-a-choice construct, so here's my counter-counter proposal:

    config BR2_TARGET_UBOOT_NEEDS_HOST_PYTHON
        bool

    choice
        bool "U-Boot needs host python"

    config BR2_TARGET_UBOOT_NEEDS_PY_NONE
        bool "none"
        depends on !BR2_TARGET_UBOOT_NEEDS_HOST_PYTHON

    config BR2_TARGET_UBOOT_NEEDS_PY2
        bool "python2"

    config BR2_TARGET_UBOOT_NEEDS_PY3
        bool "python3"

    endchoice

    config BR2_TARGET_UBOOT_NEEDS_PYLIBFDT
        bool "U-Boot needs pylibfdt"
        select BR2_TARGET_UBOOT_NEEDS_HOST_PYTHON

    config BR2_TARGET_UBOOT_NEEDS_PYELFTOOLS
        bool "U-Boot needs pyelftools"
        select BR2_TARGET_UBOOT_NEEDS_HOST_PYTHON

Yes, this is a tiny-weeny-little-bit more verbose, because there's still
the BR2_TARGET_UBOOT_NEEDS_HOST_PYTHON boolean, but it has no prompt, so
it is not user-visible, and it no longer hides the choice, just one
entry of it.

Regards,
Yann E. MORIN.

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