[PATCH] classes/machine-overrides-extended.bbclass: add

[Trevor Woerner <twoerner@gmail.com>]

Copy this class from meta-freescale so all BSPs can use it.

This class makes it easy for a BSP to specify multiple sets of configurations
for a given MACHINE. In some cases there are multiple choices for the user.
For example: for the kernel, the user could choose either the vendor kernel or
the upstream kernel. However, sometimes these decisions are "locked" together:
i.e. if you want to use the vendor's binary blob for (say) graphics, then
you have to use their vendor kernel as well. It's not possible for a user to
choose, say, the graphics binary blob but want to use the upstream kernel too.
Therefore the BSP ends up with "sets" of configurations which need to be taken
collectively instead of piecemeal.

In the example of meta-freescale, if the user does nothing special,
they get the vendor options. If they add the following line to their
configuration, they get the upstream pieces:

	MACHINEOVERRIDES .= ":use-mainline-bsp"

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
---
 meta/classes/machine-overrides-extender.bbclass | 48 +++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 meta/classes/machine-overrides-extender.bbclass

diff --git a/meta/classes/machine-overrides-extender.bbclass b/meta/classes/machine-overrides-extender.bbclass
new file mode 100644
index 0000000000..f333a0fcb7
--- /dev/null
+++ b/meta/classes/machine-overrides-extender.bbclass
@@ -0,0 +1,48 @@
+# -*- python -*-
+# Automatically set extend the MACHINEOVERRIDES
+#
+# This allow to grouping of different settings for similar platforms.
+#
+# To indicate that a SoC contains following set of overrides, you can use:
+#
+# MACHINEOVERRIDES_EXTENDER_soc = "group1:group2"
+#
+# However to indicate that an override replaces a set of other
+# overrides, you can use:
+#
+# MACHINEOVERRIDES_EXTENDER_FILTER_OUT_override = "group1 group2"
+#
+# Copyright 2016-2017 (C) O.S. Systems Software LTDA.
+
+def machine_overrides_extender(d):
+    machine_overrides = (d.getVar('MACHINEOVERRIDES', True) or '').split(':')
+
+    # Gather the list of overrides to filter out
+    machine_overrides_filter_out = []
+    for override in machine_overrides:
+        machine_overrides_filter_out += (d.getVar('MACHINEOVERRIDES_EXTENDER_FILTER_OUT_%s' % override, True) or '').split()
+
+    # Drop any overrides of filter_out prior extending
+    machine_overrides = [o for o in machine_overrides if o not in machine_overrides_filter_out]
+
+    for override in machine_overrides:
+        extender = d.getVar('MACHINEOVERRIDES_EXTENDER_%s' % override, True)
+
+        if extender:
+            extender = extender.split(':')
+
+            # Drop any extension if in filter_out
+            extender = [e for e in extender if e not in machine_overrides_filter_out]
+
+            extender.reverse()
+            if not set(extender).issubset(set(machine_overrides)):
+                index = machine_overrides.index(override)
+                for e in extender:
+                    machine_overrides.insert(index, e)
+    d.setVar('MACHINEOVERRIDES', ':'.join(machine_overrides))
+
+python machine_overrides_extender_handler() {
+    machine_overrides_extender(e.data)
+}
+machine_overrides_extender_handler[eventmask] = "bb.event.ConfigParsed"
+addhandler machine_overrides_extender_handler
-- 
2.13.0