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

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

On 08/14/2014 02:02 AM, Geert Uytterhoeven wrote:
> Hi Günther,
>
> CC kbuild
>
> On Thu, Aug 14, 2014 at 10:50 AM, Guenter Roeck <linux@roeck-us.net> wrote:
>> 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.
>
> Strange...
>
> I also saw strange things with randconfig, needing config input during the
> subsequent build, or "make oldconfig" asking new questions, just after
> having done a randconfig.
>

I made some progress. The following KCONFIG_ALLCONFIG file lets me disable GPIOLIB
with x86_64, and still build everything as modules.

# CONFIG_FB_VIA is not set
# CONFIG_MFD_AAT2870_CORE is not set
# CONFIG_MFD_ASIC3 is not set
# CONFIG_GPIOLIB is not set
CONFIG_MODULES=y

I had to deselect everything which explicitly selects GPIOLIB. Kind of makes sense.
For some reason it is necessary to specify "CONFIG_MODULES=y" even with "allmodconfig"
when using a KCONFIG_ALLCONFIG file.

Guenter