setting of BBPATH differs between ref manual and actual layer.conf file

setting of BBPATH differs between ref manual and actual layer.conf file

[Robert P. J. Day]

  admittedly picky but the ref manual here:

http://www.yoctoproject.org/docs/current/poky-ref-manual/poky-ref-manual.html#usingpoky-changes-layers

shows a sample setting of BBPATH in yocto's layer.conf:

  BBPATH := "${BBPATH}:${LAYERDIR}"

however the actual layer.conf for yocto reads:

  BBPATH := "${LAYERDIR}:${BBPATH}"

should the ordering be consistent here?  should readers be warned
about the (admittedly remote) possibility of weirdness if they happen
to try to include two layers with the same name?  is that even
possible?  does any of this even matter?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: setting of BBPATH differs between ref manual and actual layer.conf file

[Robert P. J. Day]

On Wed, 21 Mar 2012, Robert P. J. Day wrote:

>
>   admittedly picky but the ref manual here:
>
> http://www.yoctoproject.org/docs/current/poky-ref-manual/poky-ref-manual.html#usingpoky-changes-layers
>
> shows a sample setting of BBPATH in yocto's layer.conf:
>
>   BBPATH := "${BBPATH}:${LAYERDIR}"
>
> however the actual layer.conf for yocto reads:
>
>   BBPATH := "${LAYERDIR}:${BBPATH}"
>
> should the ordering be consistent here?  should readers be warned
> about the (admittedly remote) possibility of weirdness if they happen
> to try to include two layers with the same name?  is that even
> possible?  does any of this even matter?

  i really hate replying to my own posts because i forgot to do
something basic, but i did a quick grep:

$ grep -r "BBPATH :=" *
documentation/dev-manual/dev-manual-common-tasks.xml:     BBPATH := "${LAYERDIR}:${BBPATH}"
documentation/dev-manual/dev-manual-kernel-appendix.xml:     BBPATH := "${BBPATH}:${LAYERDIR}"
documentation/bsp-guide/bsp.xml:     BBPATH := "${BBPATH}:${LAYERDIR}"
meta-hob/conf/layer.conf:BBPATH := "${BBPATH}:${LAYERDIR}"
meta-skeleton/conf/layer.conf:BBPATH := "${BBPATH}:${LAYERDIR}"
meta-yocto/conf/layer.conf:BBPATH := "${LAYERDIR}:${BBPATH}"
$

  so there's a mixture of that ordering.  if there's no real reason
for that, it should really be consistent so readers don't wonder about
it.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: setting of BBPATH differs between ref manual and actual layer.conf file

[Gary Thomas]

On 2012-03-21 05:12, Robert P. J. Day wrote:
> On Wed, 21 Mar 2012, Robert P. J. Day wrote:
>
>>
>>    admittedly picky but the ref manual here:
>>
>> http://www.yoctoproject.org/docs/current/poky-ref-manual/poky-ref-manual.html#usingpoky-changes-layers
>>
>> shows a sample setting of BBPATH in yocto's layer.conf:
>>
>>    BBPATH := "${BBPATH}:${LAYERDIR}"
>>
>> however the actual layer.conf for yocto reads:
>>
>>    BBPATH := "${LAYERDIR}:${BBPATH}"
>>
>> should the ordering be consistent here?  should readers be warned
>> about the (admittedly remote) possibility of weirdness if they happen
>> to try to include two layers with the same name?  is that even
>> possible?  does any of this even matter?
>
>    i really hate replying to my own posts because i forgot to do
> something basic, but i did a quick grep:
>
> $ grep -r "BBPATH :=" *
> documentation/dev-manual/dev-manual-common-tasks.xml:     BBPATH := "${LAYERDIR}:${BBPATH}"
> documentation/dev-manual/dev-manual-kernel-appendix.xml:     BBPATH := "${BBPATH}:${LAYERDIR}"
> documentation/bsp-guide/bsp.xml:     BBPATH := "${BBPATH}:${LAYERDIR}"
> meta-hob/conf/layer.conf:BBPATH := "${BBPATH}:${LAYERDIR}"
> meta-skeleton/conf/layer.conf:BBPATH := "${BBPATH}:${LAYERDIR}"
> meta-yocto/conf/layer.conf:BBPATH := "${LAYERDIR}:${BBPATH}"
> $
>
>    so there's a mixture of that ordering.  if there's no real reason
> for that, it should really be consistent so readers don't wonder about
> it.

Indeed it does matter, as does the order that these statements are processed
(which I think is the order the layers are listed in bblayers.conf?)  It can
matter if two layers contain the same .conf file [at least].  I experienced
this when I had two layers with abi_version.conf - actually three: meta,
meta-yocto and meta-MINE - and I got very confused when I removed meta-yocto
from the mix :-(  The ordering of BBPATH isn't as important with recipes
as they use the layer priority mechanism, but if you had two layers with
identical priorities and recipes, it might matter as well.


-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
------------------------------------------------------------

Re: setting of BBPATH differs between ref manual and actual layer.conf file

[Paul Eggleton]

On Wednesday 21 March 2012 05:23:07 Gary Thomas wrote:
> Indeed it does matter, as does the order that these statements are processed
> (which I think is the order the layers are listed in bblayers.conf?) 

Correct - each layer's layer.conf will be read in the order the layers are 
listed in bblayers.conf. Since variables such as BBPATH are usually appended 
or prepended within layer.conf, you will get different final values depending on 
the order they are listed.

> It can matter if two layers contain the same .conf file [at least].  I
> experienced this when I had two layers with abi_version.conf - actually
> three: meta, meta-yocto and meta-MINE - and I got very confused when I
> removed meta-yocto from the mix :-(  

I have to say, IMHO it is best practice to not expect to be able to change 
your layer configuration and keep the same previously-built TMPDIR contents. 
Now that we've enabled OEBasicHash (in Poky) that will protect you against 
most changes that could result from playing around with your layer config by 
forcing a rebuild of the affected recipes, but if you don't have that enabled 
it's entirely possible the contents of your TMPDIR (sysroots, output packages, 
etc.) will no longer match up with the metadata.

> The ordering of BBPATH isn't as important with recipes as they use the layer
> priority mechanism, but if you had two layers with identical priorities and
> recipes, it might matter as well.

BBPATH only influences how class, configuration and include files are found. It 
has no effect on searching for recipes themselves.

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre