argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Robert P. J. Day]

  forgive me for free associating for just a few minutes, but here's
something that has the potential to be massively confusing for
beginners.

  starting with core-image.bbclass, this is just a coding philosophy
but i'm not crazy about this:

CORE_IMAGE_BASE_INSTALL = '\
    task-core-boot \
    task-base-extended \
    \
    ${CORE_IMAGE_EXTRA_INSTALL} \
    '
CORE_IMAGE_EXTRA_INSTALL ?= ""
IMAGE_INSTALL ?= "${CORE_IMAGE_BASE_INSTALL}"

  at a glance, it looks weird that IMAGE_INSTALL is simply assigned
the value of CORE_IMAGE_BASE_INSTALL, and it's only when you look up
that you notice there's a CORE_IMAGE_EXTRA_INSTALL that you can use
which is buried inside the assignment to CORE_IMAGE_BASE_INSTALL.
doing it that way forces a reader to follow the chain of assignments
to see what's happening.

  it would be much clearer to write (if it's equivalent):

CORE_IMAGE_BASE_INSTALL = '\
    task-core-boot \
    task-base-extended \
    '
CORE_IMAGE_EXTRA_INSTALL ?= ""
IMAGE_INSTALL ?= "${CORE_IMAGE_BASE_INSTALL} ${CORE_IMAGE_EXTRA_INSTALL}"

  there.  now in the space of that single line, i can see that the
*final* value for IMAGE_INSTALL comes from two other values.  and i
can even see which one appears to be the one *i* should mess with --
the one containing "EXTRA".  that construct is almost self-explanatory
and, for me, much clearer than the first one.  but wait, there's more.

  in the current *released* reference manual, there is a suggestion
for how to create custom images:

"For example, if a developer wants to add strace into the
core-image-sato image, they can use the following recipe:

     require core-image-sato.bb

     IMAGE_INSTALL += "strace"

  ok, but what's the point of having CORE_IMAGE_EXTRA_INSTALL if you
don't tell people to use it?

     require core-image-sato.bb

     CORE_IMAGE_EXTRA_INSTALL = "strace"

  are those two definitions equivalent?  is there any advantage to one
over the other?

  and finally, in the *development* version of the reference manual,
you find the new content:

file:///home/rpjday/yocto/yocto-docs/documentation/poky-ref-manual/poky-ref-manual.html#var-IMAGE_INSTALL

"When you use this variable, it is best to use it as follows:

     IMAGE_INSTALL_append = " package-name"

argh.  so what's wrong with using CORE_IMAGE_EXTRA_INSTALL?  numerous
oe-core .bb files don't take that advice -- see
core-image-minimal-mtdutils.bb:

require core-image-minimal.bb
... snip ...
IMAGE_INSTALL += "mtd-utils"

  so what is best practise here?

rday

-- 

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

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

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Eric Bénard]

Le Thu, 29 Mar 2012 15:23:20 -0400 (EDT),
"Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :
>   so what is best practise here?
> 
for this one you have an answer on OE's wiki :
http://www.openembedded.org/wiki/I_want_an_image_with_package_XYZ_installed

Eric

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Robert P. J. Day]

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On Thu, 29 Mar 2012, Eric Bénard wrote:

> Le Thu, 29 Mar 2012 15:23:20 -0400 (EDT),
> "Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :
> >   so what is best practise here?
> >
> for this one you have an answer on OE's wiki :
> http://www.openembedded.org/wiki/I_want_an_image_with_package_XYZ_installed

  despite the fact that the current reference manual *explicitly*
says this?

"Using IMAGE_INSTALL with the += operator from the /conf/local.conf
file or from within an image recipe is not recommended as it can cause
ordering issues."

  i actually did my research before i asked that question, you know.

rday

-- 

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

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

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Eric Bénard]

Le Thu, 29 Mar 2012 15:35:10 -0400 (EDT),
"Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :

> On Thu, 29 Mar 2012, Eric Bénard wrote:
> 
> > Le Thu, 29 Mar 2012 15:23:20 -0400 (EDT),
> > "Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :
> > >   so what is best practise here?
> > >
> > for this one you have an answer on OE's wiki :
> > http://www.openembedded.org/wiki/I_want_an_image_with_package_XYZ_installed
> 
>   despite the fact that the current reference manual *explicitly*
> says this?
> 
> "Using IMAGE_INSTALL with the += operator from the /conf/local.conf
> file or from within an image recipe is not recommended as it can cause
> ordering issues."
> 
>   i actually did my research before i asked that question, you know.
> 
fine, sorry for trying to give an answer to your question.

Eric

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Chris Larson]

On Thu, Mar 29, 2012 at 12:35 PM, Robert P. J. Day
<rpjday@crashcourse.ca> wrote:
> On Thu, 29 Mar 2012, Eric Bénard wrote:
>
>> Le Thu, 29 Mar 2012 15:23:20 -0400 (EDT),
>> "Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :
>> >   so what is best practise here?
>> >
>> for this one you have an answer on OE's wiki :
>> http://www.openembedded.org/wiki/I_want_an_image_with_package_XYZ_installed
>
>  despite the fact that the current reference manual *explicitly*
> says this?
>
> "Using IMAGE_INSTALL with the += operator from the /conf/local.conf
> file or from within an image recipe is not recommended as it can cause
> ordering issues."
>
>  i actually did my research before i asked that question, you know.

The two aren't conflicting. The wiki page talks about creating an
image or using bbappend, where += works fine. You have to use _append
in local.conf because it's postponed, occurs at the end of the parse.
If you use += there, the recipe will then set IMAGE_INSTALL, blowing
away the global value you +='d to.
-- 
Christopher Larson

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Robert P. J. Day]

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On Thu, 29 Mar 2012, Chris Larson wrote:

> On Thu, Mar 29, 2012 at 12:35 PM, Robert P. J. Day
> <rpjday@crashcourse.ca> wrote:
> > On Thu, 29 Mar 2012, Eric Bénard wrote:
> >
> >> Le Thu, 29 Mar 2012 15:23:20 -0400 (EDT),
> >> "Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :
> >> >   so what is best practise here?
> >> >
> >> for this one you have an answer on OE's wiki :
> >> http://www.openembedded.org/wiki/I_want_an_image_with_package_XYZ_installed
> >
> >  despite the fact that the current reference manual *explicitly*
> > says this?
> >
> > "Using IMAGE_INSTALL with the += operator from the /conf/local.conf
> > file or from within an image recipe is not recommended as it can cause
> > ordering issues."
> >
> >  i actually did my research before i asked that question, you know.
>
> The two aren't conflicting. The wiki page talks about creating an
> image or using bbappend, where += works fine. You have to use _append
> in local.conf because it's postponed, occurs at the end of the parse.
> If you use += there, the recipe will then set IMAGE_INSTALL, blowing
> away the global value you +='d to.

  i'm confused ... the current ref manual specifically (as you can
read above) discourages the use of += "from within an image recipe",
which is *precisely* what the wiki page is advocating.  so, yes, it
*is* conflicting advice.

rday

-- 

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

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

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Paul Eggleton]

On Thursday 29 March 2012 15:35:10 Robert P. J. Day wrote:
> On Thu, 29 Mar 2012, Eric Bénard wrote:
> > Le Thu, 29 Mar 2012 15:23:20 -0400 (EDT),
> > 
> > "Robert P. J. Day" <rpjday@crashcourse.ca> a écrit :
> > >   so what is best practise here?
> > 
> > for this one you have an answer on OE's wiki :
> > http://www.openembedded.org/wiki/I_want_an_image_with_package_XYZ_installe
> > d
> 
>   despite the fact that the current reference manual *explicitly*
> says this?
> 
> "Using IMAGE_INSTALL with the += operator from the /conf/local.conf
> file or from within an image recipe is not recommended as it can cause
> ordering issues."

I think what the manual is attempting to mitigate is a situation where you do 
the following in your image recipe:

-------- snip -------
IMAGE_INSTALL += "somepackage1 somepackage2"

inherit core-image
-------- snip -------

In this instance, because IMAGE_INSTALL is set via ?= within core-
image.bbclass, IMAGE_INSTALL will only be set to "somepackage1 somepackage2" 
since the value is already set by the time it gets to the ?=. This is clearly 
not what you would want by using +=.

Doing the following in an image recipe will work properly however:

-------- snip -------
inherit core-image

IMAGE_INSTALL += "somepackage1 somepackage2"
-------- snip -------

Personally I think the text you quoted from the manual should be adjusted; 
there's nothing wrong with IMAGE_INSTALL += _in an image recipe_ provided that 
you do it _after_ the inherit of core-image.

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Robert P. J. Day]

On Thu, 29 Mar 2012, Paul Eggleton wrote:

> I think what the manual is attempting to mitigate is a situation
> where you do the following in your image recipe:
>
> -------- snip -------
> IMAGE_INSTALL += "somepackage1 somepackage2"
>
> inherit core-image
> -------- snip -------
>
> In this instance, because IMAGE_INSTALL is set via ?= within core-
> image.bbclass, IMAGE_INSTALL will only be set to "somepackage1
> somepackage2" since the value is already set by the time it gets to
> the ?=. This is clearly not what you would want by using +=.
>
> Doing the following in an image recipe will work properly however:
>
> -------- snip -------
> inherit core-image
>
> IMAGE_INSTALL += "somepackage1 somepackage2"
> -------- snip -------
>
> Personally I think the text you quoted from the manual should be
> adjusted; there's nothing wrong with IMAGE_INSTALL += _in an image
> recipe_ provided that you do it _after_ the inherit of core-image.

  that makes sense, but it seems that a lot of potential confusion
could be avoided if this construct was avoided entirely and replaced
by the appropriate use of CORE_IMAGE_EXTRA_INSTALL, no?

  from my position of naivete, i can see that messing with
IMAGE_INSTALL is dangerous if you don't truly know how it's being
manipulated in the underlyling class files.

  but the solution is right there in core-image.bbclass:

CORE_IMAGE_BASE_INSTALL = '\
    task-core-boot \
    task-base-extended \
    \
    ${CORE_IMAGE_EXTRA_INSTALL} \
    '

CORE_IMAGE_EXTRA_INSTALL ?= ""

IMAGE_INSTALL ?= "${CORE_IMAGE_BASE_INSTALL}"

  that is, stop messing with IMAGE_INSTALL and do your customization
with CORE_IMAGE_EXTRA_INSTALL.  isn't that what it was expressly
designed for?

rday

-- 

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

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

Re: argh ... "_append" versus "+=" and IMAGE_INSTALL confusion

[Paul Eggleton]

On Friday 30 March 2012 06:23:39 Robert P. J. Day wrote:
>   that is, stop messing with IMAGE_INSTALL and do your customization
> with CORE_IMAGE_EXTRA_INSTALL.  isn't that what it was expressly
> designed for?

Possibly, but I had assumed though that CORE_IMAGE_EXTRA_INSTALL (and 
EXTRA_IMAGE_FEATURES) were intended to be used only from local.conf so that 
people modifying them in local.conf could never unintentionally remove things 
from the image by assigning to it directly with = as opposed to using +=.

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre