[yocto] Question: Yocto 1.7.1 kernel config defconfig will not be used?

[Bruce Ashfield]

On Mon, Mar 9, 2015 at 10:02 PM, Chung-Yeh Wang <chungyehwang at gmail.com> wrote:
> Thanks for the information, Bruce.
>
> I removed all kernel configuration fragments from the bb file but difference
> between defconfig and .config is huge. I may do something wrong and will
> study more.

There's no guarantee that the defconfig passed will end up being a perfect
match to the .config. It depends on how up to date the defconfig is, how it
was generated, etc. The kernel configuration subsystem still processes
that default config and will select, enable and disable many options that are
not part of the input defconfig.

Cheers,

Bruce

>
> Chungyeh
>
> 2015-03-09 21:02 GMT+08:00 Bruce Ashfield <bruce.ashfield at windriver.com>:
>>
>> On 15-03-09 04:36 AM, Chung-Yeh Wang wrote:
>>>
>>> Hi List,
>>>
>>> I am using Yocto 1.7.1 to build linux-mainline. I found defconfig will
>>> not be used when using linux-yocto-custom.bb
>>> <http://linux-yocto-custom.bb/> (maybe also happens on linux-yocto).
>>>
>>> I think below is the reason,
>>>
>>> 1. kernel_do_configure is run after do_kernel_configme.The last line of
>>> do_kernel_configme is echo
>>> "CONFIG_LOCALVERSION="\"${LINUX_VERSION_EXTENSION}\" >> ${B}/.config
>>>
>>> 2. Following are the code to use defconfig,
>>
>>
>> The linux-yocto kernel_configme task takes the defconfig into account,
>> and uses it along with kernel configuration fragment processing.
>>
>> The skipping of the blind defconfig copy is completely intentional.
>>
>> Cheers,
>>
>> Bruce
>>
>>
>>>
>>> # Copy defconfig to .config if .config does not exist. This allows
>>> # recipes to manage the .config themselves in do_configure_prepend().
>>> if [ -f "${WORKDIR}/defconfig" ] && [ ! -f "${B}/.config" ]; then
>>> cp "${WORKDIR}/defconfig" "${B}/.config"
>>>
>>> The condition '[ ! -f "${B}/.config"]' will not be true, so
>>> recepe-kernel/linux/linux-yocto-custom/defconfig will nerver be used.
>>>
>>>
>>> To use defconfig is one of the method suggested in Kernel developer
>>> manual.
>>>
>>> Thanks and Regards,
>>> Chungyeh
>>>
>>>
>>
>
>
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