common-tasks: Add an example of using bbappends to add a file

Use the xserver-xf86-config_%.bbappend from meta-raspberrypi to provide
an example of having a bbappend file add files to an existing recipe.

(From yocto-docs rev: f510e748ff3bcbea6e34a7f225e05628303fdd12)

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Quentin Schulz <foss@0leil.net>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 61 insertions, 0 deletions

diff --git a/documentation/dev-manual/common-tasks.rst b/documentation/dev-manual/common-tasks.rst
index 96b9fcc402..87c5a081ec 100644
--- a/documentation/dev-manual/common-tasks.rst
+++ b/documentation/dev-manual/common-tasks.rst
@@ -554,6 +554,67 @@ The end result of this ``.bbappend`` file is that on a Raspberry Pi, where
 used during :ref:`ref-tasks-fetch` and the test for a non-zero file size in
 :ref:`ref-tasks-install` will return true, and the file will be installed.
 
+Installing Additional Files Using Your Layer
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+As another example, consider the main ``xserver-xf86-config`` recipe and a
+corresponding ``xserver-xf86-config`` append file both from the :term:`Source
+Directory`.  Here is the main ``xserver-xf86-config`` recipe, which is named
+``xserver-xf86-config_0.1.bb`` and located in the "meta" layer at
+``meta/recipes-graphics/xorg-xserver``::
+
+   SUMMARY = "X.Org X server configuration file"
+   HOMEPAGE = "http://www.x.org"
+   SECTION = "x11/base"
+   LICENSE = "MIT-X"
+   LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
+   PR = "r33"
+
+   SRC_URI = "file://xorg.conf"
+
+   S = "${WORKDIR}"
+
+   CONFFILES:${PN} = "${sysconfdir}/X11/xorg.conf"
+
+   PACKAGE_ARCH = "${MACHINE_ARCH}"
+   ALLOW_EMPTY:${PN} = "1"
+
+   do_install () {
+        if test -s ${WORKDIR}/xorg.conf; then
+                install -d ${D}/${sysconfdir}/X11
+                install -m 0644 ${WORKDIR}/xorg.conf ${D}/${sysconfdir}/X11/
+        fi
+   }
+
+Following is the append file, which is named ``xserver-xf86-config_%.bbappend``
+and is from the Raspberry Pi BSP Layer named ``meta-raspberrypi``. The
+file is in the layer at ``recipes-graphics/xorg-xserver``::
+
+   FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:"
+
+   SRC_URI:append:rpi = " \
+       file://xorg.conf.d/98-pitft.conf \
+       file://xorg.conf.d/99-calibration.conf \
+   "
+   do_install:append:rpi () {
+       PITFT="${@bb.utils.contains("MACHINE_FEATURES", "pitft", "1", "0", d)}"
+       if [ "${PITFT}" = "1" ]; then
+           install -d ${D}/${sysconfdir}/X11/xorg.conf.d/
+           install -m 0644 ${WORKDIR}/xorg.conf.d/98-pitft.conf ${D}/${sysconfdir}/X11/xorg.conf.d/
+           install -m 0644 ${WORKDIR}/xorg.conf.d/99-calibration.conf ${D}/${sysconfdir}/X11/xorg.conf.d/
+       fi
+   }
+
+   FILES:${PN}:append:rpi = " ${sysconfdir}/X11/xorg.conf.d/*"
+
+Building off of the previous example, we once again are setting the
+:term:`FILESEXTRAPATHS` variable.  In this case we are also using
+:term:`SRC_URI` to list additional source files to use when ``rpi`` is found in
+the list of :term:`OVERRIDES`.  The :ref:`ref-tasks-install` task will then perform a
+check for an additional :term:`MACHINE_FEATURES` that if set will cause these
+additional files to be installed.  These additional files are listed in
+:term:`FILES` so that they will be packaged.
+
 Prioritizing Your Layer
 -----------------------