Re: [Ksummit-discuss] RFC: Kernel tinification - kernel config reduction

[Guenter Roeck <linux@roeck-us.net>]

Hi Geert,

On 08/14/2014 12:40 AM, Geert Uytterhoeven wrote:

>>>
>> Maybe something like
>>
>> make PCI=n allmodconfig
>> make GPIOLIB=n allmodconfig
>>
>> which would let me disable key options selectively so I can improve compile
>> coverage without having to go through all configurations (or randconfig).
>
> That's doable, using KCONFIG_ALLCONFIG.
>
I'll play with it some more, but a quick glance (and test) suggests that I can
only use it to force a configuration option to be true, not to force it to
be false. Also, there seems to be an odd side effect.

With
	kconfig.gpio:	"CONFIG_GPIOLIB=y"
and
	kconfig.nogpio:	"# CONFIG_GPIOLIB is not set"

KCONFIG_ALLCONFIG=kconfig.gpio make allnoconfig
	causes CONFIG_GPIOLIB to be set.

KCONFIG_ALLCONFIG=kconfig.gpio make allmodconfig
KCONFIG_ALLCONFIG=kconfig.nogpio make allmodconfig
	both have the odd and at least for me unexpected effect of disabling
	CONFIG_MODULES, but do not affect CONFIG_GPIOLIB.

>>> You also only build some of the allmodconfigs?
>>>
>> Never "only". I always also build defconfig, plus at least sometimes a couple
>> of additional configurations (if available) to improve coverage of conditional
>> functionality.
>
> Sorry, should have said "only some of the allmodconfigs".
> I noticed for e.g. m68k you build defconfig and allmodconfig (and a nommu
> config), but for some other architectures only defconfig.
>
I only use 'allmodconfig' and/or 'allyesconfig' if I can be reasonably sure
that the architecture maintainers care about it. That goes back to 3.10ish
when I started the -stable-queue builds; I only added allmodconfig/allyesconfig
to the list of builds if it built when I added the architecture. I didn't check
recently if I can add some more, so I may miss a couple of architectures
which do now build.

Guenter