[oe] RFC: "Virtual" native and sdk recipes

[Koen Kooi]

On 01-01-09 17:25, Richard Purdie wrote:
> Its nice to try something a bit different occasionally. For a long time
> the mechanical repetitive nature of -native and -sdk recipes has
> bothered me and people have talked about getting rid of them since
> forever. I've had ideas floating around on how to address this for a
> while and I now have a proper proposal and better still a proof of
> concept.
>
> Some -native recipes are already very simple, others are quite complex.
> My hypothetical foo package files contain some common constructs and
> look like:
>
> foo/foo.inc:
>
> SRC_URI = "http://somwehere/foo-${PV}.tar.bz2 \
>             file://some.patch;patch=1"
> S = "${WORKDIR}/foo-${PV}
> inherit autotools
>
> foo/foo_1.0.bb:
>
> require foo.inc
>
> foo/foo-native_1.0.bb:
> require foo_${PV}.bb
> FILESDIR = "${@os.path.dirname(bb.data.getVar('FILE',d,1))}/foo-${PV}"
> inherit native
>
> and foo/foo-1.0/some.patch exists.
>
>
> Proposal Step A:
>
> Having to set:
>
> FILESDIR = "${@os.path.dirname(bb.data.getVar('FILE',d,1))}/foo-${PV}"
>
> and
>
> S = "${WORKDIR}/foo-${PV}
>
> is fairly pointless and it would be nice the the defaults just did the
> right thing.
>
> http://git.pokylinux.org/cgit.cgi/poky/commit/?h=experimental-virtualnative&id=b8f0510a5567f6d1b90934fe513fd40423f11086
>
> is a patch introducing BASEPN which is PN with a range of specified
> suffixes removed (-native, -cross-sdk, -cross, -sdk as specified by
> SPECIAL_PKGSUFFIX).


How is the above different from the BPN used in OE?

# Base package name
# Automatically derives "foo" from "foo-native", "foo-cross" or 
"foo-initial"
# otherwise it is the same as PN and P
BPN = "${@base_package_name(d)}"
BP = "${BPN}-${PV}"

[..]

S = "${WORKDIR}/${BP}"
B = "${S}"

regards,

Koen




>
> FILESPATH and S can then be constructed with BASEPN instead of PN
> removing the need to need to hardcode them:
>
> http://git.pokylinux.org/cgit.cgi/poky/commit/?h=experimental-virtualnative&id=ed829661d51b8f23628e97404ed507c2e56d8495
>
> This reduces my hypothetical example to:
>
> foo/foo.inc:
>
> SRC_URI = "http://somwehere/${BASEPN}-${PV}.tar.bz2 \
>             file://some.patch;patch=1"
> inherit autotools
>
> foo/foo-native_1.0.bb:
> require foo_${PV}.bb
> inherit native
>
> The above proposal is worthwhile in itself alone.
>
>
> Proposal Step B:
>
> To add a new variable which is a list of classes to additionally parse
> after parsing the 'base' recipe. In the above example, foo-native-1.0.bb
> would be removed and we'd instead have:
>
> foo/foo.inc:
>
> SRC_URI = "http://somwehere/${BASEPN}-${PV}.tar.bz2 \
>             file://some.patch;patch=1"
> inherit autotools
> BBCLASSEXTEND = "native"
>
> Internally bitbake would see BBCLASSEXTEND and do something like:
>
> """
> cls = value in BBCLASSEXTEND
> data.setVar('PN', pn + '-' + cls, based)
> inherit cls
> """
>
> The big change here is that one .bb file can now provide multiple
> targets. This causes a few issues but as a hacked up proof of concept:
>
> http://git.pokylinux.org/cgit.cgi/poky/commit/?h=experimental-virtualnative&id=f614d1e2ff10938167ba6c29c49677a03b4a19ef
>
> where we append magic values to the "filename" and inherit the
> appropriate class when we notice the special names.
>
>
> The advantages of doing this are:
>
> * We can convert to the system incrementally
> * Simple syntax, the complexity is hidden in bitbake
> * Removes needless duplication but allows custom -native and -sdk
>    packages to be used where automation isn't possible/desirable
> * Parsing speed should increase since the number of full recipes we
>    parse drops and only the end stage of parsing is done for the
>    BBCLASSEXTEND packages.
> * Even just step A simplifies recipes.
>
> The disadvantages:
>
> * More complexity in bitbake (but localised mainly to cache.py)
> * The .bb file is no longer one recipe but can run in different
>    flavours which will be confusing to people
> * Would require a new bitbake release and adoption of that release
>    before OE.dev can use step B functionality. Step A functionality
>    could be added without a new bitbake by putting the special function
>    in base.bbclass instead of bitbake.
> * Certain recipe name extensions become "special". The values are not
>    hardcoded in bitbake though and its already a common convention so
>    I'm not sure this is a problem.
>
>
> I've shared my changes in a branch of Poky:
>
> http://git.pokylinux.org/cgit.cgi/poky/log/?h=experimental-virtualnative
>
> Obviously there are some heavy cleanups needed to the last bitbake
> changes but it works as a proof of concept so its time to discuss it.
>
> The main problem I currently have before being able to deploy this more
> widely is auto adjustment of DEPENDS. In most cases this consists of
> adding "-native" or "-sdk" to the values already in DEPENDS so we could
> probably add a function to native.bbclass for that. Alternatively or
> additionally, I'm considering having native.bbclass append to OVERRIDES
> so we can override DEPENDS that way instead.
>
> Comments welcome.
>
> Cheers,
>
> Richard
>