[PATCH 0/1] DISTRO_FEATURES_BACKFILL implementation

[PATCH 0/1] DISTRO_FEATURES_BACKFILL implementation

[Paul Eggleton]

Implements DISTRO_FEATURES_BACKFILL to allow introducing new
DISTRO_FEATURES that control existing functionality without breaking
existing distro configuration, as discussed in the following thread:

http://article.gmane.org/gmane.comp.handhelds.openembedded.core/13033

(No changes since the RFC except for rebasing on top of current master.)

The following changes since commit 55f72b98f606c1554eb6edd151292ffdfddf1384:

  texi2html: Fix for multilib (2012-02-22 23:01:45 +0000)

are available in the git repository at:
  git://git.openembedded.org/openembedded-core-contrib paule/distro-features-backfill
  http://cgit.openembedded.org/cgit.cgi/openembedded-core-contrib/log/?h=paule/distro-features-backfill

Paul Eggleton (1):
  conf/bitbake.conf: add DISTRO_FEATURES_BACKFILL

 meta/conf/bitbake.conf |    3 +++
 meta/lib/oe/utils.py   |   20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 0 deletions(-)

-- 
1.7.5.4

[PATCH 1/1] conf/bitbake.conf: add DISTRO_FEATURES_BACKFILL

[Paul Eggleton]

When introducing new items to DISTRO_FEATURES that control functionality
that is already enabled, in order to leave existing distro configuration
unchanged we need a way to "backfill" these new feature items onto the
existing DISTRO_FEATURES value.

This introduces a DISTRO_FEATURES_BACKFILL variable whose items will be
added to the end of DISTRO_FEATURES, unless they also appear in
DISTRO_FEATURES_BACKFILL_CONSIDERED which distros can use in their
configuration to prevent specific items from being added.

Fixes [YOCTO #1946].

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
---
 meta/conf/bitbake.conf |    3 +++
 meta/lib/oe/utils.py   |   20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index 90e5f7a..2539ae0 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -694,6 +694,9 @@ MACHINE_ESSENTIAL_EXTRA_RDEPENDS ?= ""
 MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS ?= ""
 IMAGE_FEATURES += "${EXTRA_IMAGE_FEATURES}"
 
+DISTRO_FEATURES_BACKFILL = ""
+DISTRO_FEATURES_append = "${@oe.utils.distro_features_backfill(d)}"
+
 COMBINED_FEATURES = "\
     ${@base_both_contain("DISTRO_FEATURES", "MACHINE_FEATURES", "alsa", d)} \
     ${@base_both_contain("DISTRO_FEATURES", "MACHINE_FEATURES", "bluetooth", d)} \
diff --git a/meta/lib/oe/utils.py b/meta/lib/oe/utils.py
index 95daace..2aaed3a 100644
--- a/meta/lib/oe/utils.py
+++ b/meta/lib/oe/utils.py
@@ -88,3 +88,23 @@ def param_bool(cfg, field, dflt = None):
 def inherits(d, *classes):
     """Return True if the metadata inherits any of the specified classes"""
     return any(bb.data.inherits_class(cls, d) for cls in classes)
+
+def distro_features_backfill(d):
+    # This construct allows the addition of new features to DISTRO_FEATURES
+    # that if not present would disable existing functionality, without
+    # disturbing distributions that have already set DISTRO_FEATURES.
+    # Distributions wanting to elide a value in DISTRO_FEATURES_BACKFILL should
+    # add the feature to DISTRO_FEATURES_BACKFILL_CONSIDERED
+
+    backfill = (d.getVar("DISTRO_FEATURES_BACKFILL", True) or "").split()
+    considered = (d.getVar("DISTRO_FEATURES_BACKFILL_CONSIDERED", True) or "").split()
+
+    addfeatures = []
+    for feature in backfill:
+        if feature not in considered:
+            addfeatures.append(feature)
+
+    if addfeatures:
+        return " %s" % (" ".join(addfeatures))
+    else:
+        return ""
-- 
1.7.5.4

Re: [PATCH 1/1] conf/bitbake.conf: add DISTRO_FEATURES_BACKFILL

[Richard Purdie]

On Thu, 2012-02-23 at 19:26 +0000, Paul Eggleton wrote:
> When introducing new items to DISTRO_FEATURES that control functionality
> that is already enabled, in order to leave existing distro configuration
> unchanged we need a way to "backfill" these new feature items onto the
> existing DISTRO_FEATURES value.
> 
> This introduces a DISTRO_FEATURES_BACKFILL variable whose items will be
> added to the end of DISTRO_FEATURES, unless they also appear in
> DISTRO_FEATURES_BACKFILL_CONSIDERED which distros can use in their
> configuration to prevent specific items from being added.
> 
> Fixes [YOCTO #1946].
> 
> Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
> ---
>  meta/conf/bitbake.conf |    3 +++
>  meta/lib/oe/utils.py   |   20 ++++++++++++++++++++
>  2 files changed, 23 insertions(+), 0 deletions(-)

Merged to master, thanks.

Richard