[yocto] Antwort: Re: Is it possible to add machine specific changes in a separate custom layer?

[Felix01 Fischer]

Great! Thank you Paul!
I didn't get the "Variable_$machine" part from the documentation.

One Question: I want to add changes to a %MACHINE.conf via my layer
(to be specific: I want to add "APPEND += "video=LVDS-1:d" to 
meta-intel/meta-chiefriver/conf/machine/chiefriver.conf)
Is this also possible via a separate layer? Once again, I didn't find out 
via the documentation. ATM I have to modify the chiefriver.conf directly 
:-(
Thank you for your help so far,
Regards,
Felix

Paul Eggleton <paul.eggleton at linux.intel.com> schrieb am 24.09.2013 
10:52:00:

> Von: Paul Eggleton <paul.eggleton at linux.intel.com>
> An: Felix01 Fischer <felix01.fischer at iav.de>, 
> Kopie: yocto at yoctoproject.org
> Datum: 24.09.2013 10:52
> Betreff: Re: [yocto] Is it possible to add machine specific changes 
> in a separate custom layer?
> 
> Hi Felix,
> 
> On Monday 23 September 2013 18:40:19 Felix01 Fischer wrote:
> > My goal is to build a custom-layer which supports 2 devices building 
on
> > top of the meta-intel and meta-ivi layer without changing anything 
except
> > my meta-custom layer.
> > 
> > Is it possible to have machine specific changes in a separate layer
> > building on top of  another layer?
> > I want to costumise meta-intel/meta-crownbay and
> > meta-intel/meta-chiefriver without changing something inside the
> > meta-intel layer.
> > My goal is to have modifications for the meta-intel layer in a 
meta-custom
> > layer, which only get considered if a certain MACHINE ?= "XXXX" 
(crownbay
> > or chiefriver) from the meta-intel layer is set.
> > Is this possible?
> 
> This is definitely possible - the key is to make use of bbappends and 
machine
> overrides. Append files are covered here:
> 
> http://www.yoctoproject.org/docs/current/dev-manual/dev-
> manual.html#using-bbappend-files
> 
> Overrides effectively make an assignment statement apply only when the
> specified override appears in the value of the OVERRIDES variable. For
> example:
> 
> VARIABLENAME = "the default value"
> VARIABLENAME_crownbay = "value specific to crownbay machine"
> 
> You can use append/prepend to add to the variable value instead of just
> setting it:
> 
> ANOTHERVARIABLE_append_chiefriver = " appended only for chiefriver"
> ANOTHERVARIABLE_prepend_crownbay = "prepended only for crownbay "
> 
> By default, the value of OVERRIDES includes the value of MACHINE, 
DISTRO, etc.
> If you run bitbake -e | less and then search (with /) for OVERRIDES= you 
can
> see how how OVERRIDES is constructed.
> 
> > I have the same question regarding DISTRO. I want some changes to be
> > considered if DISTRO = poky and some other changes when DISTRO =
> > poky-ivi-systemd.
> 
> Same as above only you'd be using the distro name as the override e.g.
> 
> SOMETHING_append_poky = " whatever poky-specific additions are needed"
> 
> > Is it possible to maintain these modifications in ONE custom layer or 
do I
> > need to have seperate layers (one for poky, one for poky-ivi-systemd 
and
> > machine specific changes inside the meta-intel layer)?
> 
> You don't have to, but generally we recommend keeping the machine
> customisations separate from policy (distro) customisations. This can 
make
> things easier if you have to change the machine later.
> 
> Cheers,
> Paul
> 
> -- 
> 
> Paul Eggleton
> Intel Open Source Technology Centre
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