Tom Rini wrote:
Chris Larson wrote:
On Tue, Jul 20, 2010 at 12:28 AM, Frans Meulenbroeks <
fransmeulenbro...@gmail.com> wrote:
2010/7/19 Chris Larson <clar...@kergoth.com>
On Mon, Jul 19, 2010 at 2:22 PM, Chris Larson <clar...@kergoth.com>
wrote:
On Mon, Jul 19, 2010 at 1:50 PM, Tom Rini <tom_r...@mentor.com> wrote:
Richard Purdie wrote:
Whilst our layers mechanism, is great it does have a drawback which
has
bugged me for a while. If you have a recipe like pointercal which
has
machine specific information in it and you have your new machine
code
in
a layer, how do you add a pointercal file for your machine?
Answer is you copy the whole pointercal recipe and files into your
layer, then add the single file for your machine. To me this is
ugly,
ugly, ugly. We hate code duplication and as soon as you create two
copies of the same information, we've failed.
So how could we do this better? Somehow we need to say that a given
directory X has some information which should be merged with the
original recipe. I've thought through several different ways of
doing
this and the best solution I found was "bbappend".
The idea is that if bitbake finds any X.bbappend files, when it
loads
X.bb, it will also include these files after it parses the base .bb
file
(but before finalise and the anonymous methods run). This means that
the .bbappend file can poke around and do whatever it might want to
the
recipe to customise it.
I went ahead and tried it out as its quite simple to code this in
bitbake. I liked the result enough I've already merged this into
Poky:
http://git.pokylinux.org/cgit.cgi/poky/commit/?id=63e6ba85677b8aa9f4cf9942a1fccbb8a8c72660
I'm proposing to push it to bitbake master if there are no serious
objections.
As an example use case, for the pointercal case above in another
later
you could add a pointercal_0.0.bbappend file which contained
something
like:
FILESPATH := "${FILESPATH}:$...@os.path.dirname(bb.data.getVar('FILE',
d,
True))}"
which would then cause the directory containing the bbappend file to
be
searched for pointercal files.
There are of course many other uses this could be put to for
creating
customised layers, its totally generic.
For the specific case of paths, I have wondered if there would be a
way
to leverage help from bitbake in creating a sane set of search paths
but
I'm still thinking about that. This extension is good enough in its
own
right in my opinion to be worthwhile.
I must be missing something. How is this better than amend.inc where
today you would just do:
# Just to make sure PR does change, could actually be omitted for
this
# example
$ echo 'PR .= ".1"' > mymachine/recipes/pointercal/amend.inc
$ cp /tmp/mycal mymachine/recipes/pointercal/whatever_it_is_called
? Or did you just give too trivial of an example here, and as there
are
indeed places where amend.inc falls down today, this does work?
It's the opposite. amend.inc is a bit more flexible than bbappend,
not
vice versa, but bbappend has fewer performance implications, and is
supported directly by bitbake itself (and ensures that anonymous
python
functions will work fine in appended metadata). Aside: I also suspect
that
BBCLASSEXTEND alterations will work correctly from a bbappend, which
does
not work correctly today from an amend.inc.
You'd have to be careful to lock down your appended versions when
using
bbappend, since bitbake could easily pick a newer version without the
append
out from under you, which is not an issue with amend.inc.
Although, I suppose you could set DEFAULT_PREFERENCE in the
bbappend, so
whenever you include that collection, it gets preferred.
Not if your distro decides to move to a new version. The distro choice
gets
priority to DEFAULT_PREFERENCE.
Fair point, best to use a version lockdown tool if you leverage
bbappend, at
this time, so there's a bit more work involved.
Btw is there any doc on how to use amend.inc? Looks like a neat thing.
I don't think so, but there isn't much to document. Just add INHERIT +=
"amend", and then you can place a "amend.inc" file anywhere in any
recipe's
FILESPATH, and it will be parsed and added onto the metadata of that
recipe.
Avoid modifying BBCLASSEXTEND from it, that's known to have issues.
It's also needed, in some cases, to lock down your changes via OVERRIDES
that will only match what you want to work on. For example, we're using
a snapshot with an older python, so amend.inc in our python directory
looks like:
SRC_URI_append_pn-python-native =
"file://python-2.6-r73342.patch;patch=1;pnum=0"
PARALLEL_MAKE_pn-python-native = ""
PR_append_pn-python-native .= ".1"
So that we only change python-native and not all of the other python
recipes. This would indeed not be an issue with bbappend as we'd have
put all of that into python-native_2.6.1.bbappend (but it sounds like we
would have had to add something for FILESPATH manipulation? If so, that
sounds really bad to me, Richard?).
OK, misrecollection on my part. amend.inc needs you to do some form of
mucking as well (if you want to add files or patches or ..) and in both
cases you could stick it into local.conf.
--
Tom Rini
Mentor Graphics Corporation
_______________________________________________
Openembedded-devel mailing list
Openembedded-devel@lists.openembedded.org
http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-devel
