summaryrefslogtreecommitdiff
path: root/documentation/poky-ref-manual/extendpoky.xml
diff options
context:
space:
mode:
authorRichard Purdie <rpurdie@linux.intel.com>2010-10-15 11:55:59 +0100
committerRichard Purdie <rpurdie@linux.intel.com>2010-10-15 11:55:59 +0100
commit22083287912ebd552e33b79f7c567bc966376d43 (patch)
treea16fa012a97a249e25a405d4092b0a89321bfaf6 /documentation/poky-ref-manual/extendpoky.xml
parent13a702e9e572a2dc9f6b52a1531a2237d4d98ff1 (diff)
downloadopenembedded-core-22083287912ebd552e33b79f7c567bc966376d43.tar.gz
openembedded-core-22083287912ebd552e33b79f7c567bc966376d43.tar.bz2
openembedded-core-22083287912ebd552e33b79f7c567bc966376d43.zip
handbook: Move into documentation directory
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>
Diffstat (limited to 'documentation/poky-ref-manual/extendpoky.xml')
-rw-r--r--documentation/poky-ref-manual/extendpoky.xml1040
1 files changed, 1040 insertions, 0 deletions
diff --git a/documentation/poky-ref-manual/extendpoky.xml b/documentation/poky-ref-manual/extendpoky.xml
new file mode 100644
index 0000000000..662096844d
--- /dev/null
+++ b/documentation/poky-ref-manual/extendpoky.xml
@@ -0,0 +1,1040 @@
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<chapter id='extendpoky'>
+
+<title>Extending Poky</title>
+
+ <para>
+ This section gives information about how to extend the functionality
+ already present in Poky, documenting standard tasks such as adding new
+ software packages, extending or customising images or porting poky to
+ new hardware (adding a new machine). It also contains advice about how
+ to manage the process of making changes to Poky to achieve best results.
+ </para>
+
+ <section id='usingpoky-extend-addpkg'>
+ <title>Adding a Package</title>
+
+ <para>
+ To add package into Poky you need to write a recipe for it.
+ Writing a recipe means creating a .bb file which sets various
+ variables. The variables
+ useful for recipes are detailed in the <link linkend='ref-varlocality-recipe-required'>
+ recipe reference</link> section along with more detailed information
+ about issues such as recipe naming.
+ </para>
+
+ <para>
+ Before writing a recipe from scratch it is often useful to check
+ whether someone else has written one already. OpenEmbedded is a good place
+ to look as it has a wider scope and hence a wider range of packages.
+ Poky aims to be compatible with OpenEmbedded so most recipes should
+ just work in Poky.
+ </para>
+
+ <para>
+ For new packages, the simplest way to add a recipe is to base it on a similar
+ pre-existing recipe. There are some examples below of how to add
+ standard types of packages:
+ </para>
+
+ <section id='usingpoky-extend-addpkg-singlec'>
+ <title>Single .c File Package (Hello World!)</title>
+
+ <para>
+ To build an application from a single file stored locally (e.g. under "files/")
+ requires a recipe which has the file listed in the <glossterm><link
+ linkend='var-SRC_URI'>SRC_URI</link></glossterm> variable. In addition
+ the <function>do_compile</function> and <function>do_install</function>
+ tasks need to be manually written. The <glossterm><link linkend='var-S'>
+ S</link></glossterm> variable defines the directory containing the source
+ code which in this case is set equal to <glossterm><link linkend='var-WORKDIR'>
+ WORKDIR</link></glossterm>, the directory BitBake uses for the build.
+ </para>
+ <programlisting>
+DESCRIPTION = "Simple helloworld application"
+SECTION = "examples"
+LICENSE = "MIT"
+PR = "r0"
+
+SRC_URI = "file://helloworld.c"
+
+S = "${WORKDIR}"
+
+do_compile() {
+ ${CC} helloworld.c -o helloworld
+}
+
+do_install() {
+ install -d ${D}${bindir}
+ install -m 0755 helloworld ${D}${bindir}
+}
+ </programlisting>
+
+ <para>
+ As a result of the build process "helloworld", "helloworld-dbg" and "hellworld-dev"
+ packages will be built by default. It is possible to<link linkend='usingpoky-extend-addpkg-files'>
+ customise the packaging process</link>.
+ </para>
+ </section>
+
+ <section id='usingpoky-extend-addpkg-autotools'>
+ <title>Autotooled Package</title>
+
+ <para>
+ Applications which use autotools (autoconf, automake)
+ require a recipe which has a source archive listed in
+ <glossterm><link
+ linkend='var-SRC_URI'>SRC_URI</link></glossterm> and
+ <command>inherit autotools</command> to instruct BitBake to use the
+ <filename>autotools.bbclass</filename> which has
+ definitions of all the steps
+ needed to build an autotooled application.
+ The result of the build will be automatically packaged and if
+ the application uses NLS to localise then packages with
+ locale information will be generated (one package per
+ language). Below is one example (hello_2.2.bb)
+ </para>
+
+ <programlisting>
+DESCRIPTION = "GNU Helloworld application"
+SECTION = "examples"
+LICENSE = "GPLv2+"
+LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"
+PR = "r0"
+
+SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz"
+
+inherit autotools gettext
+ </programlisting>
+
+ <para>
+ <glossterm><link linkend='var-LIC_FILES_CHKSUM'>LIC_FILES_CHKSUM</link>
+ </glossterm> is used to <link linkend='usingpoky-configuring-LIC_FILES_CHKSUM'>
+ track source license change</link>. Autotool based recipe can be quickly
+ created this way like above example.
+ </para>
+
+ </section>
+
+ <section id='usingpoky-extend-addpkg-makefile'>
+ <title>Makefile-Based Package</title>
+
+ <para>
+ Applications which use GNU make require a recipe which has
+ the source archive listed in <glossterm><link
+ linkend='var-SRC_URI'>SRC_URI</link></glossterm>.
+ Adding a <function>do_compile</function> step
+ is not needed as by default BitBake will start the "make"
+ command to compile the application. If there is a need for
+ additional options to make then they should be stored in the
+ <glossterm><link
+ linkend='var-EXTRA_OEMAKE'>EXTRA_OEMAKE</link></glossterm> variable - BitBake
+ will pass them into the GNU
+ make invocation. A <function>do_install</function> task is required
+ - otherwise BitBake will run an empty <function>do_install</function>
+ task by default.
+ </para>
+
+ <para>
+ Some applications may require extra parameters to be passed to
+ the compiler, for example an additional header path. This can
+ be done buy adding to the <glossterm><link
+ linkend='var-CFLAGS'>CFLAGS</link></glossterm> variable, as in the example below:
+ </para>
+
+ <programlisting>
+CFLAGS_prepend = "-I ${S}/include "
+ </programlisting>
+
+ <para>
+ mtd-utils is an example as Makefile-based:
+ </para>
+
+ <programlisting>
+DESCRIPTION = "Tools for managing memory technology devices."
+SECTION = "base"
+DEPENDS = "zlib lzo e2fsprogs util-linux"
+HOMEPAGE = "http://www.linux-mtd.infradead.org/"
+LICENSE = "GPLv2"
+
+SRC_URI = "git://git.infradead.org/mtd-utils.git;protocol=git;tag=v${PV}"
+
+S = "${WORKDIR}/git/"
+
+EXTRA_OEMAKE = "'CC=${CC}' 'CFLAGS=${CFLAGS} -I${S}/include -DWITHOUT_XATTR' \
+ 'BUILDDIR=${S}'"
+
+do_install () {
+ oe_runmake install DESTDIR=${D} SBINDIR=${sbindir} MANDIR=${mandir} \
+ INCLUDEDIR=${includedir}
+ install -d ${D}${includedir}/mtd/
+ for f in ${S}/include/mtd/*.h; do
+ install -m 0644 $f ${D}${includedir}/mtd/
+ done
+}
+ </programlisting>
+
+ </section>
+
+ <section id='usingpoky-extend-addpkg-files'>
+ <title>Controlling packages content</title>
+
+ <para>
+ The variables <glossterm><link
+ linkend='var-PACKAGES'>PACKAGES</link></glossterm> and
+ <glossterm><link linkend='var-FILES'>FILES</link></glossterm> are used to split an
+ application into multiple packages.
+ </para>
+
+ <para>
+ Below the "libXpm" recipe (libxpm_3.5.7.bb) is used as an example. By
+ default the "libXpm" recipe generates one package
+ which contains the library
+ and also a few binaries. The recipe can be adapted to
+ split the binaries into separate packages.
+ </para>
+
+ <programlisting>
+require xorg-lib-common.inc
+
+DESCRIPTION = "X11 Pixmap library"
+LICENSE = "X-BSD"
+DEPENDS += "libxext libsm libxt"
+PR = "r3"
+PE = "1"
+
+XORG_PN = "libXpm"
+
+PACKAGES =+ "sxpm cxpm"
+FILES_cxpm = "${bindir}/cxpm"
+FILES_sxpm = "${bindir}/sxpm"
+ </programlisting>
+
+ <para>
+ In this example we want to ship the "sxpm" and "cxpm" binaries
+ in separate packages. Since "bindir" would be packaged into the
+ main <glossterm><link linkend='var-PN'>PN</link></glossterm>
+ package as standard we prepend the <glossterm><link
+ linkend='var-PACKAGES'>PACKAGES</link></glossterm> variable so
+ additional package names are added to the start of list. The
+ extra <glossterm><link linkend='var-FILES'>FILES</link></glossterm>_*
+ variables then contain information to specify which files and
+ directories goes into which package. Files included by earlier
+ package are skipped by latter packages, and thus main <glossterm>
+ <link linkend='var-PN'>PN</link></glossterm> will not include
+ above listed files
+ </para>
+ </section>
+
+ <section id='usingpoky-extend-addpkg-postinstalls'>
+ <title>Post Install Scripts</title>
+
+ <para>
+ To add a post-installation script to a package, add
+ a <function>pkg_postinst_PACKAGENAME()</function>
+ function to the .bb file
+ where PACKAGENAME is the name of the package to attach
+ the postinst script to. Normally <glossterm><link
+ linkend='var-PN'>PN</link></glossterm> can be used which expands
+ to PACKAGENAME automatically. A post-installation function has the
+ following structure:
+ </para>
+ <programlisting>
+pkg_postinst_PACKAGENAME () {
+#!/bin/sh -e
+# Commands to carry out
+}
+ </programlisting>
+ <para>
+ The script defined in the post installation function
+ gets called when the rootfs is made. If the script succeeds,
+ the package is marked as installed. If the script fails,
+ the package is marked as unpacked and the script will be
+ executed again on the first boot of the image.
+ </para>
+
+ <para>
+ Sometimes it is necessary that the execution of a post-installation
+ script is delayed until the first boot, because the script
+ needs to be executed on the device itself. To delay script execution
+ until boot time, the post-installation function should have the
+ following structure:
+ </para>
+
+ <programlisting>
+pkg_postinst_PACKAGENAME () {
+#!/bin/sh -e
+if [ x"$D" = "x" ]; then
+ # Actions to carry out on the device go here
+else
+ exit 1
+fi
+}
+ </programlisting>
+
+ <para>
+ The structure above delays execution until first boot
+ because the <glossterm><link
+ linkend='var-D'>D</link></glossterm> variable points
+ to the 'image'
+ directory when the rootfs is being made at build time but
+ is unset when executed on the first boot.
+ </para>
+ </section>
+
+ </section>
+
+ <section id='usingpoky-extend-customimage'>
+ <title>Customising Images</title>
+
+ <para>
+ Poky images can be customised to satisfy
+ particular requirements. Several methods are detailed below
+ along with guidelines of when to use them.
+ </para>
+
+ <section id='usingpoky-extend-customimage-custombb'>
+ <title>Customising Images through a custom image .bb files</title>
+
+ <para>
+ One way to get additional software into an image is by creating a
+ custom image. The recipe will contain two lines:
+ </para>
+
+ <programlisting>
+IMAGE_INSTALL = "task-poky-x11-base package1 package2"
+
+inherit poky-image
+ </programlisting>
+
+ <para>
+ By creating a custom image, a developer has total control
+ over the contents of the image. It is important to use
+ the correct names of packages in the <glossterm><link
+ linkend='var-IMAGE_INSTALL'>IMAGE_INSTALL</link></glossterm> variable.
+ The names must be in
+ the OpenEmbedded notation instead of Debian notation, for example
+ "glibc-dev" instead of "libc6-dev" etc.
+ </para>
+
+ <para>
+ The other method of creating a new image is by modifying
+ an existing image. For example if a developer wants to add
+ "strace" into "poky-image-sato" the following recipe can
+ be used:
+ </para>
+
+ <programlisting>
+require poky-image-sato.bb
+
+IMAGE_INSTALL += "strace"
+ </programlisting>
+
+ </section>
+
+ <section id='usingpoky-extend-customimage-customtasks'>
+ <title>Customising Images through custom tasks</title>
+
+ <para>
+ For complex custom images, the best approach is to create a custom
+ task package which is then used to build the image (or images). A good
+ example of a tasks package is <filename>meta/packages/tasks/task-poky.bb
+ </filename>. The <glossterm><link linkend='var-PACKAGES'>PACKAGES</link></glossterm>
+ variable lists the task packages to build (along with the complementary
+ -dbg and -dev packages). For each package added,
+ <glossterm><link linkend='var-PACKAGES'>RDEPENDS</link></glossterm> and
+ <glossterm><link linkend='var-PACKAGES'>RRECOMMENDS</link></glossterm>
+ entries can then be added each containing a list of packages the parent
+ task package should contain. An example would be:
+ </para>
+
+ <para>
+ <programlisting>
+DESCRIPTION = "My Custom Tasks"
+
+PACKAGES = "\
+ task-custom-apps \
+ task-custom-apps-dbg \
+ task-custom-apps-dev \
+ task-custom-tools \
+ task-custom-tools-dbg \
+ task-custom-tools-dev \
+ "
+
+RDEPENDS_task-custom-apps = "\
+ dropbear \
+ portmap \
+ psplash"
+
+RDEPENDS_task-custom-tools = "\
+ oprofile \
+ oprofileui-server \
+ lttng-control \
+ lttng-viewer"
+
+RRECOMMENDS_task-custom-tools = "\
+ kernel-module-oprofile"
+</programlisting>
+ </para>
+
+ <para>
+ In this example, two task packages are created, task-custom-apps and
+ task-custom-tools with the dependencies and recommended package dependencies
+ listed. To build an image using these task packages, you would then add
+ "task-custom-apps" and/or "task-custom-tools" to <glossterm><link
+ linkend='var-IMAGE_INSTALL'>IMAGE_INSTALL</link></glossterm> or other forms
+ of image dependencies as described in other areas of this section.
+ </para>
+ </section>
+
+ <section id='usingpoky-extend-customimage-imagefeatures'>
+ <title>Customising Images through custom <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm></title>
+
+ <para>
+ Ultimately users may want to add extra image "features" as used by Poky with the
+ <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm>
+ variable. To create these, the best reference is <filename>meta/classes/poky-image.bbclass</filename>
+ which illustrates how poky achieves this. In summary, the file looks at the contents of the
+ <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm>
+ variable and then maps this into a set of tasks or packages. Based on this then the
+ <glossterm><link linkend='var-IMAGE_INSTALL'> IMAGE_INSTALL</link></glossterm>
+ variable is generated automatically. Extra features can be added by
+ extending the class or creating a custom class for use with specialised image .bb files.
+ </para>
+ </section>
+
+ <section id='usingpoky-extend-customimage-localconf'>
+ <title>Customising Images through local.conf</title>
+
+ <para>
+ It is possible to customise image contents by abusing
+ variables used by distribution maintainers in local.conf.
+ This method only allows the addition of packages and
+ is not recommended.
+ </para>
+
+ <para>
+ To add an "strace" package into the image the following is
+ added to local.conf:
+ </para>
+
+ <programlisting>
+DISTRO_EXTRA_RDEPENDS += "strace"
+ </programlisting>
+
+ <para>
+ However, since the <glossterm><link linkend='var-DISTRO_EXTRA_RDEPENDS'>
+ DISTRO_EXTRA_RDEPENDS</link></glossterm> variable is for
+ distribution maintainers this method does not make
+ adding packages as simple as a custom .bb file. Using
+ this method, a few packages will need to be recreated if they have been
+ created before and then the image is rebuilt.
+ </para>
+ <programlisting>
+bitbake -c clean task-boot task-base task-poky
+bitbake poky-image-sato
+ </programlisting>
+
+ <para>
+ Cleaning task-* packages is required because they use the
+ <glossterm><link linkend='var-DISTRO_EXTRA_RDEPENDS'>
+ DISTRO_EXTRA_RDEPENDS</link></glossterm> variable. There is no need to
+ build them by hand as Poky images depend on the packages they contain so
+ dependencies will be built automatically when building the image. For this reason we don't use the
+ "rebuild" task in this case since "rebuild" does not care about
+ dependencies - it only rebuilds the specified package.
+ </para>
+
+ </section>
+
+ </section>
+
+<section id="platdev-newmachine">
+ <title>Porting Poky to a new machine</title>
+ <para>
+ Adding a new machine to Poky is a straightforward process and
+ this section gives an idea of the changes that are needed. This guide is
+ meant to cover adding machines similar to those Poky already supports.
+ Adding a totally new architecture might require gcc/glibc changes as
+ well as updates to the site information and, whilst well within Poky's
+ capabilities, is outside the scope of this section.
+ </para>
+
+ <section id="platdev-newmachine-conffile">
+ <title>Adding the machine configuration file</title>
+ <para>
+ A .conf file needs to be added to conf/machine/ with details of the
+ device being added. The name of the file determines the name Poky will
+ use to reference this machine.
+ </para>
+
+ <para>
+ The most important variables to set in this file are <glossterm>
+ <link linkend='var-TARGET_ARCH'>TARGET_ARCH</link></glossterm>
+ (e.g. "arm"), <glossterm><link linkend='var-PREFERRED_PROVIDER'>
+ PREFERRED_PROVIDER</link></glossterm>_virtual/kernel (see below) and
+ <glossterm><link linkend='var-MACHINE_FEATURES'>MACHINE_FEATURES
+ </link></glossterm> (e.g. "kernel26 apm screen wifi"). Other variables
+ like <glossterm><link linkend='var-SERIAL_CONSOLE'>SERIAL_CONSOLE
+ </link></glossterm> (e.g. "115200 ttyS0"), <glossterm>
+ <link linkend='var-KERNEL_IMAGETYPE'>KERNEL_IMAGETYPE</link>
+ </glossterm> (e.g. "zImage") and <glossterm><link linkend='var-IMAGE_FSTYPES'>
+ IMAGE_FSTYPES</link></glossterm> (e.g. "tar.gz jffs2") might also be
+ needed. Full details on what these variables do and the meaning of
+ their contents is available through the links. There're lots of existing
+ machine .conf files which can be easily leveraged from meta/conf/machine/.
+ </para>
+ </section>
+
+ <section id="platdev-newmachine-kernel">
+ <title>Adding a kernel for the machine</title>
+ <para>
+ Poky needs to be able to build a kernel for the machine. You need
+ to either create a new kernel recipe for this machine or extend an
+ existing recipe. There are plenty of kernel examples in the
+ meta/recipes-kernel/linux directory which can be used as references.
+ </para>
+ <para>
+ If creating a new recipe the "normal" recipe writing rules apply
+ for setting up a <glossterm><link linkend='var-SRC_URI'>SRC_URI
+ </link></glossterm> including any patches and setting <glossterm>
+ <link linkend='var-S'>S</link></glossterm> to point at the source
+ code. You will need to create a configure task which configures the
+ unpacked kernel with a defconfig be that through a "make defconfig"
+ command or more usually though copying in a suitable defconfig and
+ running "make oldconfig". By making use of "inherit kernel" and also
+ maybe some of the linux-*.inc files, most other functionality is
+ centralised and the the defaults of the class normally work well.
+ </para>
+ <para>
+ If extending an existing kernel it is usually a case of adding a
+ suitable defconfig file in a location similar to that used by other
+ machine's defconfig files in a given kernel, possibly listing it in
+ the SRC_URI and adding the machine to the expression in <glossterm>
+ <link linkend='var-COMPATIBLE_MACHINE'>COMPATIBLE_MACHINE</link>
+ </glossterm>:
+ </para>
+ <programlisting>
+COMPATIBLE_MACHINE = '(qemux86|qemumips)'
+ </programlisting>
+ </section>
+
+ <section id="platdev-newmachine-formfactor">
+ <title>Adding a formfactor configuration file</title>
+ <para>
+ A formfactor configuration file provides information about the
+ target hardware on which Poky is running, and that Poky cannot
+ obtain from other sources such as the kernel. Some examples of
+ information contained in a formfactor configuration file include
+ framebuffer orientation, whether or not the system has a keyboard,
+ the positioning of the keyboard in relation to the screen, and
+ screen resolution.
+ </para>
+ <para>
+ Sane defaults should be used in most cases, but if customisation is
+ necessary you need to create a <filename>machconfig</filename> file
+ under <filename>meta/packages/formfactor/files/MACHINENAME/</filename>
+ where <literal>MACHINENAME</literal> is the name for which this infomation
+ applies. For information about the settings available and the defaults, please see
+ <filename>meta/packages/formfactor/files/config</filename>. Below is one
+ example for qemuarm:
+ </para>
+ <programlisting>
+HAVE_TOUCHSCREEN=1
+HAVE_KEYBOARD=1
+
+DISPLAY_CAN_ROTATE=0
+DISPLAY_ORIENTATION=0
+#DISPLAY_WIDTH_PIXELS=640
+#DISPLAY_HEIGHT_PIXELS=480
+#DISPLAY_BPP=16
+DISPLAY_DPI=150
+DISPLAY_SUBPIXEL_ORDER=vrgb
+ </programlisting>
+ </section>
+</section>
+
+<section id='usingpoky-changes'>
+ <title>Making and Maintaining Changes</title>
+
+ <para>
+ We recognise that people will want to extend/configure/optimise Poky for
+ their specific uses, especially due to the extreme configurability and
+ flexibility Poky offers. To ensure ease of keeping pace with future
+ changes in Poky we recommend making changes to Poky in a controlled way.
+ </para>
+ <para>
+ Poky supports the idea of <link
+ linkend='usingpoky-changes-layers'>"layers"</link> which when used
+ properly can massively ease future upgrades and allow segregation
+ between the Poky core and a given developer's changes. Some other advice on
+ managing changes to Poky is also given in the following section.
+ </para>
+
+ <section id="usingpoky-changes-layers">
+ <title>Bitbake Layers</title>
+
+ <para>
+ Often, people want to extend Poky either through adding packages
+ or overriding files contained within Poky to add their own
+ functionality. Bitbake has a powerful mechanism called
+ layers which provides a way to handle this extension in a fully
+ supported and non-invasive fashion.
+ </para>
+
+ <para>
+ The Poky tree includes several additional layers which demonstrate
+ this functionality, such as meta-emenlow and meta-extras.
+ The meta-emenlow layer is an example layer enabled by default. The meta-extras
+ repostory is not enabled by default but enabling any layer is as easy as adding
+ the layers path to the BBLAYERS variable in your bblayers.conf. this is how
+ meta-extras are enabled in Poky builds:
+ </para>
+ <para>
+ <literallayout class='monospaced'>LCONF_VERSION = "1"
+
+BBFILES ?= ""
+BBLAYERS = " \
+ /path/to/poky/meta \
+ /path/to/poky/meta-moblin \
+ /path/to/poky/meta-emenlow \
+ /path/to/poky/meta-extras \
+ "
+</literallayout>
+ </para>
+
+ <para>
+ Bitbake parses the conf/layer.conf of each of the layers in BBLAYERS
+ to add the layers packages, classes and configuration to Poky.
+ To create your own layer, independent of the main Poky repository,
+ you need only create a directory with a conf/layer.conf file and
+ add the directory to your bblayers.conf.
+ </para>
+
+ <para>
+ The meta-emenlow/conf/layer.conf demonstrates the required syntax:
+ <literallayout class='monospaced'># We have a conf and classes directory, add to BBPATH
+BBPATH := "${BBPATH}:${LAYERDIR}"
+
+# We have a packages directory, add to BBFILES
+BBFILES := "${BBFILES} ${LAYERDIR}/packages/*/*.bb \
+ ${LAYERDIR}/packages/*/*.bbappend"
+
+BBFILE_COLLECTIONS += "emenlow"
+BBFILE_PATTERN_emenlow := "^${LAYERDIR}/"
+BBFILE_PRIORITY_emenlow = "6"
+ </literallayout>
+ </para>
+
+ <para>
+ As can be seen, the layers recipes are added to
+ <glossterm> <link linkend='var-BBFILES'>BBFILES</link></glossterm>. The
+ BBFILE_COLLECTIONS variable is then appended to with the
+ layer name. The BBFILE_PATTERN variable is immediately expanded
+ with a regular expression used to match files from BBFILES into
+ a particular layer, in this case by using the base pathname.
+ The BBFILE_PRIORITY variable then assigns different
+ priorities to the files in different layers. This is useful
+ in situations where the same package might appear in multiple
+ layers and allows you to choose which layer should 'win'.
+ Note the use of <glossterm><link linkend='var-LAYERDIR'>
+ LAYERDIR</link></glossterm> with the immediate expansion operator.
+ <glossterm><link linkend='var-LAYERDIR'>LAYERDIR</link></glossterm>
+ expands to the directory of the current layer and
+ requires use of the immediate expansion operator so that Bitbake
+ does not lazily expand the variable when it's parsing a
+ different directory.
+ </para>
+
+ <para>
+ Additional bbclass and configuration files can be locationed by
+ bitbake through the addition to the BBPATH
+ environment variable. In this case, the first file with the
+ matching name found in BBPATH is the one that is used, just
+ like the PATH variable for binaries. It is therefore recommended
+ that you use unique bbclass and configuration file names in your
+ custom layer.
+ </para>
+
+ <para>
+ The recommended approach for custom layers is to store them in a
+ git repository of the format meta-prvt-XXXX and have this repository
+ cloned alongside the other meta directories in the Poky tree.
+ This way you can keep your Poky tree and it's configuration entirely
+ inside POKYBASE.
+ </para>
+ </section>
+
+ <section id='usingpoky-changes-commits'>
+ <title>Committing Changes</title>
+
+ <para>
+ Modifications to Poky are often managed under some kind of source
+ revision control system. The policy for committing to such systems
+ is important as some simple policy can significantly improve
+ usability. The tips below are based on the policy followed for the
+ Poky core.
+ </para>
+
+ <para>
+ It helps to use a consistent style for commit messages when committing
+ changes. We've found a style where the first line of a commit message
+ summarises the change and starts with the name of any package affected
+ work well. Not all changes are to specific packages so the prefix could
+ also be a machine name or class name instead. If a change needs a longer
+ description this should follow the summary:
+ </para>
+
+ <literallayout class='monospaced'>
+ bitbake/data.py: Add emit_func() and generate_dependencies() functions
+
+ These functions allow generation of dependency data between funcitons and
+ variables allowing moves to be made towards generating checksums and allowing
+ use of the dependency information in other parts of bitbake.
+
+ Signed-off-by: Richard Purdie rpurdie@linux.intel.com
+ </literallayout>
+
+ <para>
+ Any commit should be self contained in that it should leave the
+ metadata in a consistent state, buildable before and after the
+ commit. This helps ensure the autobuilder test results are valid
+ but is good practice regardless.
+ </para>
+ </section>
+
+ <section id='usingpoky-changes-prbump'>
+ <title>Package Revision Incrementing</title>
+
+ <para>
+ If a committed change will result in changing the package output
+ then the value of the <glossterm><link linkend='var-PR'>PR</link>
+ </glossterm> variable needs to be increased (commonly referred to
+ as 'bumped') as part of that commit. Only integer values are used
+ and <glossterm><link linkend='var-PR'>PR</link></glossterm> =
+ "r0" should be added into new recipes as, while this is the
+ default value, not having the variable defined in a recipe makes
+ it easy to miss incrementing it when updating the recipe.
+ When upgrading the version of a package (<glossterm><link
+ linkend='var-PV'>PV</link></glossterm>), the <glossterm><link
+ linkend='var-PR'>PR</link></glossterm> variable should be reset to "r0".
+ </para>
+
+ <para>
+ The aim is that the package version will only ever increase. If
+ for some reason <glossterm><link linkend='var-PV'>PV</link></glossterm>
+ will change and but not increase, the <glossterm><link
+ linkend='var-PE'>PE</link></glossterm> (Package Epoch) can
+ be increased (it defaults to '0'). The version numbers aim to
+ follow the <ulink url='http://www.debian.org/doc/debian-policy/ch-controlfields.html'>
+ Debian Version Field Policy Guidelines</ulink> which define how
+ versions are compared and hence what "increasing" means.
+ </para>
+
+ <para>
+ There are two reasons for doing this, the first is to ensure that
+ when a developer updates and rebuilds, they get all the changes to
+ the repository and don't have to remember to rebuild any sections.
+ The second is to ensure that target users are able to upgrade their
+ devices via their package manager such as with the <command>
+ opkg upgrade</command> commands (or similar for
+ dpkg/apt or rpm based systems). The aim is to ensure Poky has
+ upgradable packages in all cases.
+ </para>
+ </section>
+ <section id='usingpoky-changes-collaborate'>
+ <title>Using Poky in a Team Environment</title>
+
+ <para>
+ It may not be immediately clear how Poky can work in a team environment,
+ or scale to a large team of developers. The specifics of any situation
+ will determine the best solution and poky offers immense flexibility in
+ that aspect but there are some practises that experience has shown to work
+ well.
+ </para>
+
+ <para>
+ The core component of any development effort with Poky is often an
+ automated build testing framework and image generation process. This
+ can be used to check that the metadata is buildable, highlight when
+ commits break the builds and provide up to date images allowing people
+ to test the end result and use them as a base platform for further
+ development. Experience shows that buildbot is a good fit for this role
+ and that it works well to configure it to make two types of build -
+ incremental builds and 'from scratch'/full builds. The incremental builds
+ can be tied to a commit hook which triggers them each time a commit is
+ made to the metadata and are a useful acid test of whether a given commit
+ breaks the build in some serious way. They catch lots of simple errors
+ and whilst they won't catch 100% of failures, the tests are fast so
+ developers can get feedback on their changes quickly. The full builds
+ are builds that build everything from the ground up and test everything.
+ They usually happen at preset times such as at night when the machine
+ load isn't high from the incremental builds.
+ <ulink url='http://autobuilder.pokylinux.org:8010'>poky autobuilder</ulink>
+ is an example implementation with buildbot.
+ </para>
+
+ <para>
+ Most teams have pieces of software undergoing active development. It is of
+ significant benefit to put these under control of a source control system
+ compatible with Poky such as git or svn. The autobuilder can then be set to
+ pull the latest revisions of these packages so the latest commits get tested
+ by the builds allowing any issues to be highlighted quickly. Poky easily
+ supports configurations where there is both a stable known good revision
+ and a floating revision to test. Poky can also only take changes from specific
+ source control branches giving another way it can be used to track/test only
+ specified changes.
+ </para>
+ <para>
+ Perhaps the hardest part of setting this up is the policy that surrounds
+ the different source control systems, be them software projects or the Poky
+ metadata itself. The circumstances will be different in each case but this is
+ one of Poky's advantages - the system itself doesn't force any particular policy
+ unlike a lot of build systems, allowing the best policy to be chosen for the
+ circumstances.
+ </para>
+ </section>
+
+ <section id='usingpoky-changes-updatingimages'>
+ <title>Updating Existing Images</title>
+
+ <para>
+ Often, rather than reflashing a new image you might wish to install updated
+ packages into an existing running system. This can be done by sharing the <filename class="directory">tmp/deploy/ipk/</filename> directory through a web server and then on the device, changing <filename>/etc/opkg/base-feeds.conf</filename> to point at this server, for example by adding:
+ </para>
+ <literallayout class='monospaced'>
+src/gz all http://www.mysite.com/somedir/deploy/ipk/all
+src/gz armv7a http://www.mysite.com/somedir/deploy/ipk/armv7a
+src/gz beagleboard http://www.mysite.com/somedir/deploy/ipk/beagleboard</literallayout>
+ </section>
+ </section>
+
+ <section id='usingpoky-modifing-packages'>
+ <title>Modifying Package Source Code</title>
+
+ <para>
+ Poky is usually used to build software rather than modifying
+ it. However, there are ways Poky can be used to modify software.
+ </para>
+
+ <para>
+ During building, the sources are available in <glossterm><link
+ linkend='var-WORKDIR'>WORKDIR</link></glossterm> directory.
+ Where exactly this is depends on the type of package and the
+ architecture of target device. For a standard recipe not
+ related to <glossterm><link
+ linkend='var-MACHINE'>MACHINE</link></glossterm> it will be
+ <filename>tmp/work/PACKAGE_ARCH-poky-TARGET_OS/PN-PV-PR/</filename>.
+ Target device dependent packages use <glossterm><link
+ linkend='var-MACHINE'>MACHINE
+ </link></glossterm>
+ instead of <glossterm><link linkend='var-PACKAGE_ARCH'>PACKAGE_ARCH
+ </link></glossterm>
+ in the directory name.
+ </para>
+
+ <tip>
+ <para>
+ Check the package recipe sets the <glossterm><link
+ linkend='var-S'>S</link></glossterm> variable to something
+ other than standard <filename>WORKDIR/PN-PV/</filename> value.
+ </para>
+ </tip>
+ <para>
+ After building a package, a user can modify the package source code
+ without problem. The easiest way to test changes is by calling the
+ "compile" task:
+ </para>
+
+ <programlisting>
+bitbake -c compile -f NAME_OF_PACKAGE
+ </programlisting>
+
+ <para>
+ "-f" or "--force" is used to force re-execution of the specified task.
+ Other tasks may also be called this way. But note that all the modifications
+ in <glossterm><link linkend='var-WORKDIR'>WORKDIR</link></glossterm>
+ are gone once you executes "-c clean" for a package.
+ </para>
+
+ <section id='usingpoky-modifying-packages-quilt'>
+ <title>Modifying Package Source Code with quilt</title>
+
+ <para>
+ By default Poky uses <ulink
+ url='http://savannah.nongnu.org/projects/quilt'>quilt</ulink>
+ to manage patches in <function>do_patch</function> task.
+ It is a powerful tool which can be used to track all
+ modifications done to package sources.
+ </para>
+
+ <para>
+ Before modifying source code it is important to
+ notify quilt so it will track changes into new patch
+ file:
+ <programlisting>
+quilt new NAME-OF-PATCH.patch
+ </programlisting>
+
+ Then add all files which will be modified into that
+ patch:
+ <programlisting>
+quilt add file1 file2 file3
+ </programlisting>
+
+ Now start editing. At the end quilt needs to be used
+ to generate final patch which will contain all
+ modifications:
+ <programlisting>
+quilt refresh
+ </programlisting>
+
+ The resulting patch file can be found in the
+ <filename class="directory">patches/</filename> subdirectory of the source
+ (<glossterm><link linkend='var-S'>S</link></glossterm>) directory. For future builds it
+ should be copied into
+ Poky metadata and added into <glossterm><link
+ linkend='var-SRC_URI'>SRC_URI</link></glossterm> of a recipe:
+ <programlisting>
+SRC_URI += "file://NAME-OF-PATCH.patch"
+ </programlisting>
+
+ This also requires a bump of <glossterm><link
+ linkend='var-PR'>PR</link></glossterm> value in the same recipe as we changed resulting packages.
+ </para>
+
+ </section>
+
+ </section>
+ <section id='usingpoky-configuring-LIC_FILES_CHKSUM'>
+ <title>Track license change</title>
+ <para>
+ The license of one upstream project may change in the future, and Poky provides
+ one mechanism to track such license change - <glossterm>
+ <link linkend='var-LIC_FILES_CHKSUM'>LIC_FILES_CHKSUM</link></glossterm> variable.
+ </para>
+
+ <section id='usingpoky-specifying-LIC_FILES_CHKSUM'>
+ <title>Specifying the LIC_FILES_CHKSUM variable </title>
+
+ <programlisting>
+LIC_FILES_CHKSUM = "file://COPYING; md5=xxxx \
+ file://licfile1.txt; beginline=5; endline=29;md5=yyyy \
+ file://licfile2.txt; endline=50;md5=zzzz \
+ ..."
+ </programlisting>
+
+ <para>
+ <glossterm><link linkend='var-S'>S</link></glossterm> is the default directory
+ for searching files listed in <glossterm><link linkend='var-LIC_FILES_CHKSUM'>
+ LIC_FILES_CHKSUM</link></glossterm>. Relative path could be used too:
+ </para>
+
+ <programlisting>
+LIC_FILES_CHKSUM = "file://src/ls.c;startline=5;endline=16;\
+ md5=bb14ed3c4cda583abc85401304b5cd4e"
+LIC_FILES_CHKSUM = "file://../license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
+ </programlisting>
+
+ <para>
+ The first line locates a file in <glossterm><link linkend='var-S'>
+ S</link></glossterm>/src/ls.c, and the second line refers to a file in
+ <glossterm><link linkend='var-WORKDIR'>WORKDIR</link></glossterm>, which is the parent
+ of <glossterm><link linkend='var-S'>S</link></glossterm>
+ </para>
+
+ </section>
+
+ <section id='usingpoky-LIC_FILES_CHKSUM-explanation-of-syntax'>
+ <title>Explanation of syntax</title>
+
+ <para>
+ This parameter lists all the important files containing the text
+of licenses for the
+source code. It is also possible to specify on which line the license text
+starts and on which line it ends within that file using the "beginline" and
+"endline" parameters. If the "beginline" parameter is not specified then license
+text begins from the 1st line is assumed. Similarly if "endline" parameter is
+not specified then the license text ends at the last line in the file is
+assumed. So if a file contains only licensing information, then there is no need
+to specify "beginline" and "endline" parameters.
+ </para>
+ <para>
+The "md5" parameter stores the md5 checksum of the license text. So if
+the license text changes in any way from a file, then its md5 sum will differ and will not
+match with the previously stored md5 checksum. This mismatch will trigger build
+failure, notifying developer about the license text md5 mismatch, and allowing
+the developer to review the license text changes. Also note that if md5 checksum
+is not matched while building, the correct md5 checksum is printed in the build
+log which can be easily copied to .bb file.
+ </para>
+ <para>
+There is no limit on how many files can be specified on this parameter. But generally every
+project would need specifying of just one or two files for license tracking.
+Many projects would have a "COPYING" file which will store all the
+license information for all the source code files. If the "COPYING" file
+is valid then tracking only that file would be enough.
+ </para>
+ <tip>
+ <para>
+1. If you specify empty or invalid "md5" parameter; then while building
+the package, bitbake will give md5 not matched error, and also show the correct
+"md5" parameter value both on the screen and in the build log
+ </para>
+ <para>
+2. If the whole file contains only license text, then there is no need to
+specify "beginline" and "endline" parameters.
+ </para>
+ </tip>
+ </section>
+ </section>
+ <section id='usingpoky-configuring-DISTRO_PN_ALIAS'>
+ <title>Handle package name alias</title>
+ <para>
+Poky implements a distro_check task which automatically connects to major distributions
+and checks whether they contains same package. Sometimes the same package has different
+names in different distributions, which results in a mismatch from distro_check task
+This can be solved by defining per distro recipe name alias -
+<glossterm><link linkend='var-DISTRO_PN_ALIAS'>DISTRO_PN_ALIAS</link></glossterm>
+ </para>
+
+ <section id='usingpoky-specifying-DISTRO_PN_ALIAS'>
+ <title>Specifying the DISTRO_PN_ALIAS variable </title>
+
+ <programlisting>
+DISTRO_PN_ALIAS_pn-PACKAGENAME = "distro1=package_name_alias1 \
+ distro2=package_name_alias2 \
+ distro3=package_name_alias3 \
+ ..."
+ </programlisting>
+ <para>
+Use space as the delimiter if there're multiple distro aliases
+ </para>
+ <tip>
+ <para>
+The current code can check if the src package for a recipe exists in the latest
+releases of these distributions automatically.
+ </para>
+ <programlisting>
+Fedora, OpenSuSE, Debian, Ubuntu, Mandriva
+ </programlisting>
+ <para>
+For example, this command will generate a report, listing which linux distros include the
+sources for each of the poky recipe.
+ </para>
+ <programlisting>
+bitbake world -f -c distro_check
+ </programlisting>
+ <para>
+The results will be stored in the build/tmp/log/distro_check-${DATETIME}.results file.
+ </para>
+ </tip>
+ </section>
+ </section>
+</chapter>
+
+<!--
+vim: expandtab tw=80 ts=4
+-->