rework patch model

At the Buildroot Developers Meeting (4-5 February 2013, in Brussels) a change
to the patch logic was discussed. See

http://elinux.org/Buildroot:DeveloperDaysFOSDEM2013

for details. In summary:

* For patches stored in the package directory, if
  package/<pkg>/<version>/ does exist, apply package/<pkg>/<version>/*.patch,
  otherwise, apply package/<pkg>/*.patch
* For patches stored in the global patches directory, if
  $(GLOBAL_PATCH_DIR)/<pkg>/<version>/ does exist, apply
  $(GLOBAL_PATCH_DIR)/<pkg>/<version>/*.patch, otherwise, apply
  $(GLOBAL_PATCH_DIR)/<pkg>/*.patch

This patch adds the new BR2_GLOBAL_PATCH_DIR configuration item, and reworks
the generic package infrastructure to implement the new patch logic.

[Peter: fixup doc nits as pointed out by Thomas]
Signed-off-by: Simon Dawson <spdawson@gmail.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

Config.in

@@ -437,6 +437,21 @@ config BR2_PACKAGE_OVERRIDE_FILE
 	  as the source directory for a particular package. See the
 	  Buildroot documentation for more details on this feature.
 
+config BR2_GLOBAL_PATCH_DIR
+	string "global patch directory"
+	help
+	  You may specify a directory containing global package patches.
+	  For a specific version <packageversion> of a specific package
+	  <packagename>, patches are applied as follows.
+
+	  First, the default Buildroot patch set for the package is applied.
+
+	  If the directory $(BR2_GLOBAL_PATCH_DIR)/<packagename>/<packageversion>
+	  exists, then all *.patch files in the directory will be applied.
+
+	  Otherwise, if the directory $(BR2_GLOBAL_PATCH_DIR)/<packagename> exists,
+	  then all *.patch files in the directory will be applied.
+
 endmenu
 
 source "toolchain/Config.in"

docs/manual/customize-packages.txt

@@ -0,0 +1,23 @@
+// -*- mode:doc -*- ;
+
+[[packages-custom]]
+Customizing packages
+~~~~~~~~~~~~~~~~~~~~
+
+It is sometimes useful to apply 'extra' patches to packages - over and
+above those provided in Buildroot. This might be used to support custom
+features in a project, for example, or when working on a new architecture.
+
+The +BR2_GLOBAL_PATCH_DIR+ configuration file option can be
+used to specify a directory containing global package patches.
+
+For a specific version <packageversion> of a specific package <packagename>,
+patches are applied as follows.
+
+First, the default Buildroot patch set for the package is applied.
+
+If the directory +$(BR2_GLOBAL_PATCH_DIR)/<packagename>/<packageversion>+
+exists, then all +*.patch+ files in the directory will be applied.
+
+Otherwise, if the directory +$(BR2_GLOBAL_PATCH_DIR)/<packagename>+
+exists, then all +*.patch+ files in the directory will be applied.

docs/manual/customize.txt

@@ -15,3 +15,5 @@ include::customize-kernel-config.txt[]
 include::customize-toolchain.txt[]
 
 include::customize-store.txt[]
+
+include::customize-packages.txt[]

docs/manual/patch-policy.txt

@@ -11,8 +11,9 @@ necessary to patch the source of the software to get it cross-built within
 Buildroot.
 
 Buildroot offers an infrastructure to automatically handle this during
-the builds. It supports two ways of applying patch sets: downloaded patches
-and patches supplied within buildroot.
+the builds. It supports three ways of applying patch sets: downloaded patches,
+patches supplied within buildroot and patches located in a user-defined
+global patch directory.
 
 Providing patches
 ~~~~~~~~~~~~~~~~~
@@ -45,6 +46,13 @@ application order.
 reference in their filename.
 - The field +<number>+ in the patch file name refers to the 'apply order'.
 
+Global patch directory
+^^^^^^^^^^^^^^^^^^^^^^
+
+The +BR2_GLOBAL_PATCH_DIR+ configuration file option can be
+used to specify a directory containing global package patches. See
+xref:packages-custom[] for details.
+
 
 How patches are applied
 ~~~~~~~~~~~~~~~~~~~~~~~
@@ -57,7 +65,7 @@ How patches are applied
   tarballs are applied;
 
 . If there are some +*.patch+ files in the package directory or in the
-  a package subdirectory named +<packagename>-<packageversion>+, then:
+  a package subdirectory named +<packageversion>+, then:
 +
 * If a +series+ file exists in the package directory, then patches are
   applied according to the +series+ file;

package/pkg-generic.mk

@@ -82,21 +82,21 @@ endif
 # find the package directory (typically package/<pkgname>) and the
 # prefix of the patches
 $(BUILD_DIR)/%/.stamp_patched: NAMEVER = $(RAWNAME)-$($(PKG)_VERSION)
+$(BUILD_DIR)/%/.stamp_patched: PATCH_BASE_DIRS = $($(PKG)_DIR_PREFIX)/$(RAWNAME) $(call qstrip,$(BR2_GLOBAL_PATCH_DIR))/$(RAWNAME)
 $(BUILD_DIR)/%/.stamp_patched:
 	@$(call MESSAGE,"Patching $($(PKG)_DIR_PREFIX)/$(RAWNAME)")
 	$(foreach hook,$($(PKG)_PRE_PATCH_HOOKS),$(call $(hook))$(sep))
 	$(foreach p,$($(PKG)_PATCH),support/scripts/apply-patches.sh $(@D) $(DL_DIR) $(p)$(sep))
 	$(Q)( \
-	if test -d $($(PKG)_DIR_PREFIX)/$(RAWNAME); then \
-	  if test "$(wildcard $($(PKG)_DIR_PREFIX)/$(RAWNAME)/$(NAMEVER)*.patch*)"; then \
-	    support/scripts/apply-patches.sh $(@D) $($(PKG)_DIR_PREFIX)/$(RAWNAME) $(NAMEVER)\*.patch $(NAMEVER)\*.patch.$(ARCH) || exit 1; \
-	  else \
-	    support/scripts/apply-patches.sh $(@D) $($(PKG)_DIR_PREFIX)/$(RAWNAME) $(RAWNAME)\*.patch $(RAWNAME)\*.patch.$(ARCH) || exit 1; \
-	    if test -d $($(PKG)_DIR_PREFIX)/$(RAWNAME)/$(NAMEVER); then \
-	      support/scripts/apply-patches.sh $(@D) $($(PKG)_DIR_PREFIX)/$(RAWNAME)/$(NAMEVER) \*.patch \*.patch.$(ARCH) || exit 1; \
+	for D in $(PATCH_BASE_DIRS); do \
+	  if test -d $${D}; then \
+	    if test -d $${D}/$($(PKG)_VERSION); then \
+	      support/scripts/apply-patches.sh $(@D) $${D}/$($(PKG)_VERSION) \*.patch \*.patch.$(ARCH) || exit 1; \
+	    else \
+	      support/scripts/apply-patches.sh $(@D) $${D} \*.patch \*.patch.$(ARCH) || exit 1; \
 	    fi; \
 	  fi; \
-	fi; \
+	done; \
 	)
 	$(foreach hook,$($(PKG)_POST_PATCH_HOOKS),$(call $(hook))$(sep))
 	$(Q)touch $@