[Buildroot] [PATCH 02/11] arch: MIPS: Add config option BR2_GCC_TARGET_TUNE

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

Paul, All,

On 2014-04-05 17:53 +0200, Paul Cercueil spake thusly:
> On 04/04/2014 00:12, Yann E. MORIN wrote:
[--SNIP--]
> >Can you double-check that it is indeed working for you? Because if it
> >does, we have a really big bug in Kconfig (Oh, no, not one more...)
> 
> I confirm it works.

I checked your patch:

    $ cat defconfig
    BR2_mips=y
    BR2_GCC_TARGET_TUNE="mips32r2"

    $ make BR2_DEFCONFIG=$(pwd)/defconfig defconfig
    [...]

    $ grep BR2_GCC_TARGET_TUNE .config
    BR2_GCC_TARGET_TUNE="mips32"

So no, it does not work as you explained you were expecting it to work:

    ---
    This patch would pass the same value to --with-arch and --with-tune, 
    unless you define a different value for BR2_GCC_TARGET_TUNE in your 
    defconfig. We use that for the Ingenic jz4740 processor, which is a 
    mips32 processor but running better the code tuned for mips32r2.
    ---

From what I understand, you have a defconfig file where you manually
wrote:
    BR2_GCC_TARGET_TUNE="mips32r2"

But as shown above, that does not work.

> Why is it a bug?

Because, for a prompt-less value, kconfig is expected to discard any
value and only use the 'default' values. And from the above, it is what
is hapenning: a value from a defconfig is properly over-written by what
kconfig computes for this prompt-less value.

So I stand on my position: I NAK this patch, because it does not fix the
explained reason for it.

Regards,
Yann E. MORIN.

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