[yocto] When to create a new build directory for yocto?

[ChenQi]

On 12/01/2014 03:04 PM, Qiang Yu wrote:
> What about MACHINE_FEATURES and IMAGE_FEATURES?
>

IMAGE_FEATURES is OK.
MACHINE_FEATURES is like DISTRO_FEATURES. Things are not ensured to work 
correctly if you change it in the same build directory.

If I were you, I would jut let builds to share sstate and downloads and 
use different build directories for each combination of 'machine + 
distro + feature'.
E.g.
build-qemux86-64-poky-systemd-pam
build-qemux86-64-poky-systemd
build-qemux86-64-poky-sysvinit-pam
....

This would ensure a clean upgrade path.

//Chen Qi

>
> On Mon, Dec 1, 2014 at 1:28 PM, ChenQi <Qi.Chen at windriver.com 
> <mailto:Qi.Chen at windriver.com>> wrote:
>
>     On 12/01/2014 12:45 PM, Qiang Yu wrote:
>>
>>
>>         It's possible that you are using (or might use) different
>>         layer configurations for different builds.
>>         One build might have a bbappend file that another build
>>         doesn't need.
>>
>>     Yes, you are right. I use different conf/bblayers.conf for
>>     different SOC. But within the same SOC's different output
>>     (board image, SDK), I just change MACHINE and SDKMACHINE. Is it
>>     safe to build all outputs of the same SOC
>>     in one build dir?
>
>     Yes.
>
>>         Also, different builds may have different DISTRO_FEATURES.
>>         Thus, having different deploy directories is better.
>>         Otherwise, your package feeds might be broken. And you would
>>         suffer trying to maintain it.
>>
>>     You mean I can't build two output with different DISTRO_FEATURES
>>     in the same build dir.
>>     Any other config var? What about MACHINE and SDKMACHINE?
>
>     Yocto doesn't ensure that changing distro features in the same
>     build directory works.
>     It might work, but it's also possible that it doesn't.
>
>     Changing MACHINE and SDKMACHINE is OK.
>
>     //Chen Qi
>
>

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