more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Robert P. J. Day]

  (most of this is sort of self-evident but it's not documented as
well as it could be so i just want to make sure i have it exactly
right.)

  snippets of some layer.conf files:

oe-core:

BBPATH .= ":${LAYERDIR}"
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"

meta-hob:

BBPATH := "${BBPATH}:${LAYERDIR}"
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"

meta-yocto:

BBPATH := "${LAYERDIR}:${BBPATH}"
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
            ${LAYERDIR}/recipes-*/*/*.bbappend"

  note how meta-hob *appends* itself to BBPATH, while meta-yocto
*prepends* itself.  is there no possibility that this will cause some
confusion based on how BBPATH is used to resolve the location of class
or conf files?  i realize you should try to avoid that sort of
conflict but it still seems possible that someone might choose the
names of some files badly and the unpredictable ordering in BBPATH
will cause grief, no?

rday

-- 

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

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

Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Andrei Gherzan]

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On Sun, Jul 8, 2012 at 8:59 PM, Robert P. J. Day <rpjday@crashcourse.ca>wrote:

>
>   (most of this is sort of self-evident but it's not documented as
> well as it could be so i just want to make sure i have it exactly
> right.)
>
>   snippets of some layer.conf files:
>
> oe-core:
>
> BBPATH .= ":${LAYERDIR}"
> BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"
>
> meta-hob:
>
> BBPATH := "${BBPATH}:${LAYERDIR}"
> BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
>
> meta-yocto:
>
> BBPATH := "${LAYERDIR}:${BBPATH}"
> BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
>             ${LAYERDIR}/recipes-*/*/*.bbappend"
>
>   note how meta-hob *appends* itself to BBPATH, while meta-yocto
> *prepends* itself.  is there no possibility that this will cause some
> confusion based on how BBPATH is used to resolve the location of class
> or conf files?  i realize you should try to avoid that sort of
> conflict but it still seems possible that someone might choose the
> names of some files badly and the unpredictable ordering in BBPATH
> will cause grief, no?
>
>
I don't think this can cause any problems. It's all about the order the
files are searched. As long as you have proper priority set nothing can go
wrong.

@g

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Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Robert P. J. Day]

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On Mon, 9 Jul 2012, Andrei Gherzan wrote:

>
> On Sun, Jul 8, 2012 at 8:59 PM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
>
>         (most of this is sort of self-evident but it's not documented as
>       well as it could be so i just want to make sure i have it exactly
>       right.)
>
>         snippets of some layer.conf files:
>
>       oe-core:
>
>       BBPATH .= ":${LAYERDIR}"
>       BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"
>
>       meta-hob:
>
>       BBPATH := "${BBPATH}:${LAYERDIR}"
>       BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
>
>       meta-yocto:
>
>       BBPATH := "${LAYERDIR}:${BBPATH}"
>       BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
>                   ${LAYERDIR}/recipes-*/*/*.bbappend"
>
>         note how meta-hob *appends* itself to BBPATH, while meta-yocto
>       *prepends* itself.  is there no possibility that this will cause some
>       confusion based on how BBPATH is used to resolve the location of class
>       or conf files?  i realize you should try to avoid that sort of
>       conflict but it still seems possible that someone might choose the
>       names of some files badly and the unpredictable ordering in BBPATH
>       will cause grief, no?
>
>
> I don't think this can cause any problems.

  are you sure?

> It's all about the order the files are searched. As long as you have
> proper priority set nothing can go wrong.

  but what if two or more layers have the same priority?  then what?
it may be that there's no issue here, i'm just pointing out the
possibility that, given the inconsistent way layers add themelves to
BBPATH (either prepending or appending) and the order one lists the
layers in bblayers.conf, is there absolutely no chance that someone
could experience unexpected behaviour given an unusual combination of
circumstances?

rday

-- 

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

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

Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Andrei Gherzan]

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On Mon, Jul 9, 2012 at 11:34 PM, Robert P. J. Day <rpjday@crashcourse.ca>wrote:

> On Mon, 9 Jul 2012, Andrei Gherzan wrote:
>
> >
> > On Sun, Jul 8, 2012 at 8:59 PM, Robert P. J. Day <rpjday@crashcourse.ca>
> wrote:
> >
> >         (most of this is sort of self-evident but it's not documented as
> >       well as it could be so i just want to make sure i have it exactly
> >       right.)
> >
> >         snippets of some layer.conf files:
> >
> >       oe-core:
> >
> >       BBPATH .= ":${LAYERDIR}"
> >       BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"
> >
> >       meta-hob:
> >
> >       BBPATH := "${BBPATH}:${LAYERDIR}"
> >       BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
> >
> >       meta-yocto:
> >
> >       BBPATH := "${LAYERDIR}:${BBPATH}"
> >       BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
> >                   ${LAYERDIR}/recipes-*/*/*.bbappend"
> >
> >         note how meta-hob *appends* itself to BBPATH, while meta-yocto
> >       *prepends* itself.  is there no possibility that this will cause
> some
> >       confusion based on how BBPATH is used to resolve the location of
> class
> >       or conf files?  i realize you should try to avoid that sort of
> >       conflict but it still seems possible that someone might choose the
> >       names of some files badly and the unpredictable ordering in BBPATH
> >       will cause grief, no?
> >
> >
> > I don't think this can cause any problems.
>
>   are you sure?
>
>
As i said, as long as PRIORITY is set accordingly.

@g

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Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Paul Eggleton]

On Monday 09 July 2012 16:34:20 Robert P. J. Day wrote:
> On Mon, 9 Jul 2012, Andrei Gherzan wrote:
> > It's all about the order the files are searched. As long as you have
> > proper priority set nothing can go wrong.
> 
>   but what if two or more layers have the same priority?  then what?
> it may be that there's no issue here, i'm just pointing out the
> possibility that, given the inconsistent way layers add themelves to
> BBPATH (either prepending or appending) and the order one lists the
> layers in bblayers.conf, is there absolutely no chance that someone
> could experience unexpected behaviour given an unusual combination of
> circumstances?

To avoid confusion, layer priorities are only applicable with regard to 
recipes/bbappends. To respond to your question, if two layers have the same 
priority (which is legal) then if there is a situation where a recipe file is 
provided by both layers, which one "wins" will depend on the order they appear 
in bblayers.conf.

The BBPATH variable is completely independent of this, and is the path that is 
used to find conf and bbclass files; however, the order in which the appends / 
prepends will be applied is of course the order in which they are parsed, 
which is the order in which they appear in bblayers.conf. Most layers should 
be appending to BBPATH rather than prepending but there may be exceptions.

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre

Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Robert P. J. Day]

On Mon, 9 Jul 2012, Paul Eggleton wrote:

> The BBPATH variable is completely independent of this, and is the
> path that is used to find conf and bbclass files; however, the order
> in which the appends / prepends will be applied is of course the
> order in which they are parsed, which is the order in which they
> appear in bblayers.conf. Most layers should be appending to BBPATH
> rather than prepending but there may be exceptions.

  and that was my basic issue -- that some layers append while others
prepend might cause unexpected behaviour, but i've made my point so
i'll shut up now.

rday

-- 

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

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

Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Martin Jansa]

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On Sun, Jul 08, 2012 at 01:59:48PM -0400, Robert P. J. Day wrote:
> 
>   (most of this is sort of self-evident but it's not documented as
> well as it could be so i just want to make sure i have it exactly
> right.)
> 
>   snippets of some layer.conf files:
> 
> oe-core:
> 
> BBPATH .= ":${LAYERDIR}"
> BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"
> 
> meta-hob:
> 
> BBPATH := "${BBPATH}:${LAYERDIR}"
> BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
> 
> meta-yocto:
> 
> BBPATH := "${LAYERDIR}:${BBPATH}"
> BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
>             ${LAYERDIR}/recipes-*/*/*.bbappend"
> 
>   note how meta-hob *appends* itself to BBPATH, while meta-yocto
> *prepends* itself.  is there no possibility that this will cause some
> confusion based on how BBPATH is used to resolve the location of class
> or conf files?  i realize you should try to avoid that sort of
> conflict but it still seems possible that someone might choose the
> names of some files badly and the unpredictable ordering in BBPATH
> will cause grief, no?

Yes, order is important and prepending makes it harder for person
writting bblayers.conf to influence it:

http://lists.linuxtogo.org/pipermail/openembedded-core/2012-July/024914.html

http://lists.linuxtogo.org/pipermail/openembedded-core/2012-February/018115.html:
BBFILE_PRIORITY controls recipe priority. BBLAYERS order controls
BBPATH order which in turn controls bbclass/config priority, as things
stand today.

See also this thread for more details:
http://lists.linuxtogo.org/pipermail/openembedded-devel/2011-May/032387.html

Cheers,

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa@gmail.com

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Re: more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Martin Jansa]

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On Mon, Jul 09, 2012 at 11:23:32AM +0200, Martin Jansa wrote:
> On Sun, Jul 08, 2012 at 01:59:48PM -0400, Robert P. J. Day wrote:
> > 
> >   (most of this is sort of self-evident but it's not documented as
> > well as it could be so i just want to make sure i have it exactly
> > right.)
> > 
> >   snippets of some layer.conf files:
> > 
> > oe-core:
> > 
> > BBPATH .= ":${LAYERDIR}"
> > BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"
> > 
> > meta-hob:
> > 
> > BBPATH := "${BBPATH}:${LAYERDIR}"
> > BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
> > 
> > meta-yocto:
> > 
> > BBPATH := "${LAYERDIR}:${BBPATH}"
> > BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
> >             ${LAYERDIR}/recipes-*/*/*.bbappend"
> > 
> >   note how meta-hob *appends* itself to BBPATH, while meta-yocto
> > *prepends* itself.  is there no possibility that this will cause some
> > confusion based on how BBPATH is used to resolve the location of class
> > or conf files?  i realize you should try to avoid that sort of
> > conflict but it still seems possible that someone might choose the
> > names of some files badly and the unpredictable ordering in BBPATH
> > will cause grief, no?
> 
> Yes, order is important and prepending makes it harder for person
> writting bblayers.conf to influence it:
> 
> http://lists.linuxtogo.org/pipermail/openembedded-core/2012-July/024914.html
> 
> http://lists.linuxtogo.org/pipermail/openembedded-core/2012-February/018115.html:
> BBFILE_PRIORITY controls recipe priority. BBLAYERS order controls
> BBPATH order which in turn controls bbclass/config priority, as things
> stand today.
> 
> See also this thread for more details:
> http://lists.linuxtogo.org/pipermail/openembedded-devel/2011-May/032387.html

And this one
http://lists.linuxtogo.org/pipermail/openembedded-core/2011-August/007387.html

Cheers,

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa@gmail.com

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