path: root/distribution/yocto-basic/pres_yocto-basic.tex

\input{configpres}

\title{YOCTO - Basics}
\maketitle

\begin{frame}
\frametitle{Bitbake Overview}
\begin{itemize}
\item Classes
\item Recipes
\item Layers
\item Append files
\item Tasks
\item Machines
\item Build configuration
\item Boundary Sabrelite Imagebuild
\item TI Beaglebone Black Imagebuild
\item Commands and Debug methods
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Variable assignments}
\begin{itemize}
\item =
\item ?=
\item ??=
\item :=
\item += / =+
\item .= / =.
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{Variable assignment with =}
\begin{verbatim}
VAR = "value"
\end{verbatim}
\begin{itemize}
	\item normal assignment
	\item values need to be surrounded by double quotes
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{early default assignment with ?=}
\begin{verbatim}
VAR ?= "1"
VAR ?= "2"
\end{verbatim}
\begin{itemize}
	\item VAR is set to "1" in this example
	\item if there are multiple assignments using ?= the first one is used
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{late default assignment with ??=}
\begin{verbatim}
VAR ??= "1"
VAR ??= "2"
\end{verbatim}
\begin{itemize}
	\item VAR is set to "2" in this example
	\item if there are multiple assignments using ??= the last one is used
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{assignment priorities \#1}
\begin{verbatim}
VAR_A ??= "12"
VAR_A ?= "34"

VAR_B ?= "12"
VAR_B ??= "34"
\end{verbatim}
\begin{itemize}
	\item VAR\_A contains "34"
	\item VAR\_B contains "12"
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{assignment priorities \#2}
\begin{verbatim}
VAR ?= "12"
VAR ??= "34"
VAR = "56"
VAR ?= "78"
VAR ??= "78"
\end{verbatim}
\begin{itemize}
	\item VAR contains "56"
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{immediate variable expansion with :=}
\begin{verbatim}
VAR_A = "11"
VAR_B = "B:${VAR_A}"
VAR_A = "22"
VAR_C := "C:${VAR_A}"
VAR_A = "33"
echo ${VAR_A} ${VAR_B} ${VAR_C}
\end{verbatim}
\begin{itemize}
	\item 33 B:33 C:22
	\item the content of VAR\_C is expanded immediately on assignment
	\item the content of VAR\_B is expanded on use
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{append (+=) or prepend (=+) a variable}
\begin{verbatim}
VAR_A = "12"
VAR_A += "34"
VAR_B = "56"
VAR_B =+ "78"
\end{verbatim}
\begin{itemize}
	\item VAR\_A contains "12 34"
	\item VAR\_B contains "78 56"
	\item there are spaces between the appended values
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{append (.=) or prepend (=.) a variable}
\begin{verbatim}
VAR_A = "12"
VAR_A .= "34"
VAR_B = "56"
VAR_B =. "78"
\end{verbatim}
\begin{itemize}
	\item VAR\_A contains "1234"
	\item VAR\_B contains "7856"
	\item there are no spaces between the appended values
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{assignment debugging}
\begin{verbatim}
$ echo 'FOO ??= "123"' >> conf/local.conf
$ echo 'FOO ?= "456"' >> conf/local.conf

$ bitbake -e | grep FOO
# $FOO [2 operations]
FOO="456"
\end{verbatim}
\end{frame}

\begin{frame}
\frametitle{Classes}
\begin{itemize}
\item denoted by the .bbclass extension
\item base.bbclass is automatically included by all other classes and recipes.
\item common tasks and there execution order is defined in base.bbclass
\item tasks can be added, overridden, extended or used by other classes
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Recipes}
\begin{itemize}
\item a .bb file inherits classes and populates them with data
\item bitbake is used to schedule the tasks defined in a recipe
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Layers}
\begin{itemize}
\item used to isolate different types of customizations from each other
\item e.g. own layer for machine specific stuff, one for own applications
\item .bbappend files are used to modify recipes from another layer
\item 'conf/layer.conf' is used to define the recipe location(s)
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Layers}
Layers are a way to manage extensions, and customizations to the system.

Layers
\begin{itemize}
\item extend, add, replace or modify recipes
\item add or replace bbclass files
\item add or modify configuration settings
\item are added and ordered via BBLAYERS variable in build/conf/bblayers.conf
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Layers}
Best Practice: Layers should be grouped by functionality
\begin{itemize}
\item Custom Toolchains (compilers, debuggers, profiling tools)
\item Distribution specifications (i.e. meta-yocto)
\item BSP/Machine settings (i.e. meta-yocto-bsp)
\item Functional areas (selinux, networking, etc)
\item Project specific changes
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{typical recipe progressing}
\begin{enumerate}
\item fetch source files
\item extract sources
\item patch sources
\item configure sources
\item compilation
\item packaging
\end{enumerate}
\end{frame}

\begin{frame}[fragile]
\frametitle{recipe skeleton}
\begin{verbatim}
SUMMARY = "short description of the package (1 line)"
DESCRIPTION = "a long version of the description of the package"
HOMEPAGE = "http://url-of-the-os-project.org"
LICENSE = "LGPLv2.1"

LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \
                    file://licfile1.txt;beginline=5;endline=29;md5=yyyy \
                    file://licfile2.txt;endline=50;md5=zzzz

SRC_URI = "file://mysw-1.0.tbz"
SRC_URI[md5sum] = "xxx"
SRC_URI[sha256sum] = "yyy"

S = "${WORKDIR}/${PN}-${PV}"

inherit autotools
\end{verbatim}
\end{frame}

\begin{frame}
\frametitle{recipe syntax}
a recipe normaly consists of a human readable description of the project and
references to the open-source project and:
\begin{description}
\item[LIC*] reference to the used licenses
\item[SRC\_URI] list of source files (local or remote)
\item[PV] package-version (retrived from filename name\_version.bb)
\item[PN] package-name (retrived from filename name\_version.bb)
\item[P] ${PN}-${PV}
\item[S] The location in the Build Directory where unpacked recipe source code resides.
\item[inherit] use a class (or multiple classes)
\end{description}
\end{frame}

\begin{frame}
\frametitle{the LICENSE variable}
list of source licenses for the recipe:
\begin{itemize}
\item do not use spaces within individual license names
\item use spaces between license names
\item separate license names using | (pipe) when there is a choice between
 licenses
\item separate license names using \& (AND) if parts of the code are licensed
 with different licenses
\item for standard licenses, use the names of the files in
 meta/files/common-licenses/ or the SPDXLICENSEMAP
 \footnote{aps commonly used license names to their SPDX counterparts found in
 meta/files/common-licenses/. For the default SPDXLICENSEMAP mappings, see the
 meta/conf/licenses.conf file}
 flag names defined in meta/conf/licenses.conf
\item use "CLOSED" for closed source software
 (LIC\_FILES\_CHKSUM is not needed to be defined then)
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{LIC\_FILE\_CHKSUM variable}
Checksums of the license text in the recipe source code.


This variable tracks changes in license text of the source code files.
If the license text is changed, it will trigger a build failure,
which gives the developer an opportunity to review any license change.
\end{frame}

\begin{frame}[fragile]
\frametitle{SRC\_URI variable}
\begin{verbatim}
SRC_URI = "<protocol>://<host>/<path>;<OptionA=xxx>;<OptionB=xxx>"
\end{verbatim}
multiple urls can be set in a SRC\_URI variable:
\begin{verbatim}
SRC_URI = "<url1>;name=url1 <url2>;name=url2"
\end{verbatim}
for each url a md5 and sha256 checksum needs to be added:
\begin{verbatim}
SRC_URI[url1.md5sum] = xxx
SRC_URI[url1.sha256sum] = yyy
SRC_URI[url2.md5sum] = zzz
SRC_URI[url2.sha256sum] = xyz
\end{verbatim}
To get these checksums don't specify them and run a build and copy them from
the error message. (Don't use md5sum or sha256sum on the commandline; they
produce a different checksum.)
\end{frame}

\begin{frame}
\frametitle{local SRC\_URI (file://)}
The path is relative to the FILESPATH variable. To modify the FILESPATH use
FILESEXTRAPATH.

Additional files are searched in subdirectories of the directory in which the
recipe file (.bb) or append file (.bbappend) resides:
\begin{description}
\item[\${BPN}] base recipe name without any special suffix or version numbers.
\item[\${BP} - \${BPN}-\${PV}] base recipe name and version but without any special package name suffix.
\item[files] files within a directory, which is named files and is also alongside the recipe or append file. 
\end{description}
\end{frame}

\begin{frame}
\frametitle{the BPN variable}
\begin{itemize}
\item bare name of the recipe
\item version of PN but without suffixes specified in SPECIAL\_PKGSUFFIX
  (-common, -native, -cross)
\item version of PN but without prefixes specified in MLPREFIX (lib64-, lib32-)
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{remote SRC\_URI}
\begin{description}
\item[bzr://]Bazaar revision control repository
\item[git://]Git revision control repository
\item[osc://]OSC (OpenSUSE Build service) revision control repository
\item[ccrc://]ClearCase repository
\item[http://]Internet using http
\item[https://]Internet using https
\item[ftp://]Internet using ftp
\item[cvs://]CVS revision control repository
\item[hg://]Mercurial (hg) revision control repository
\item[p4://]Perforce (p4) revision control repository
\item[ssh://]secure shell
\item[svn://]Subversion (svn) revision control repository
\end{description}
\end{frame}

\begin{frame}
\frametitle{SRC\_URI patch options}
standard options
\begin{description}
\item[apply=no] apply patch or not; default is yes
\item[striplevel=0] striplevel to use when applying a patch; default is 1
\item[patchdir=\${S}/foo] directory in which the patch should be applied;
 default is \${S}
\end{description}
\end{frame}
\begin{frame}
\frametitle{SRC\_URI patch options \#2}
specific options
\begin{description}
\item[mindate] apply patch only if SRCDATE
 \footnote{The date of the source code used to build the package.
 This variable applies only if the source was fetched from a
 Source Code Manager (SCM)} is equal to or greater than mindate
\item[maxdate] apply patch only if SRCDATE is not later than maxdate
\item[minrev] apply the patch only if SRCREV
 \footnote{The revision of the source code used to build the package.
 This variable applies to Subversion, Git, Mercurial and Bazaar only}
 is equal to or greater than minrev
\item[maxrev] apply patch only if SRCREV is not later than maxrev
\item[rev] apply patch only if SRCREV is equal to rev
\item[notrev] apply patch only if SRCREV is not equal to rev
\end{description}
\end{frame}

\begin{frame}
\frametitle{SRC\_URI options}
\begin{description}
\item[unpack=no] controls if an archive is unpacked; default is yes
\item[subdir=bla] places the file (or extracts its contents) into the
 specified subdirectory of WORKDIR
 \footnote{${TMPDIR}/work/${MULTIMACH\_TARGET\_SYS}/${PN}/${EXTENDPE}${PV}-${PR}; 
 eg. poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0}
\item[name=mydl] name to be used for association with SRC\_URI checksums when
 you have more than one file specified in SRC\_URI
\item[downloadfilename=my.tar.gz] the filename used when storing the downloaded file
\end{description}
\end{frame}

\begin{frame}
\frametitle{inherit}
inherit is used to use the functionality defined in a .bblcass file. Popular
predefined classes are:
\begin{itemize}
\item allarch
\item archiver
\item autotools / autotools-brokensep
\item bin\_package
\item cmake
\item cpan
\item distutils / setuptools
\item kernel / module
\item mime
\item qmake / qmake2
\item qt4e / qt4x11
\item scons
\item systemd
\item u-boot
\item vala
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Append files}
a append file must be named after the base package:

<base-pn>\_<base-pv>.bbappend

<base-pv> can be replaced by \% to match all versions.

They are typically used to modify or extend the functionality of the base
recipe.

It's recommended by the Yocto project to use bbappend files instead of copying
and modyfiing a recipe in an own layer.
\end{frame}

\begin{frame}
\frametitle{Tasks}
\begin{description}
\item [do\_bundle\_initramfs] combines an initial ramdisk image and kernel
	together to form a single image
\item [do\_checkuri] validates the SRC\_URI value
\item [do\_checkuriall] validates the SRC\_URI value for all recipes required
	to build a target"
\item [do\_clean] removes all output files for a target
\item [do\_cleanall] removes all output files, shared state cache, and
	downloaded source files for a target
\item [do\_cleansstate] removes all output files and shared state cache for a
	target
\item [do\_compile] compiles the source in the compilation directory
\item [do\_compile\_kernelmodules] compiles loadable modules for the Linux
	kernel
\item [do\_compile\_ptest\_base] compiles the runtime test suite included in
	the software being built
\item [do\_configure] configures the source by enabling and disabling any
	build-time and configuration options for the software being built
\item [do\_configure\_ptest\_base] configures the runtime test suite included
	in the software being built
\item [do\_deploy] writes deployable output files to the deploy directory
\item [do\_devshell] starts a shell with the environment set up for
	development/debugging
\item [do\_diffconfig] compares the old and new config files after running
	do\_menuconfig for the kernel
\item [do\_fetch] fetches the source code
\item [do\_fetchall] fetches all remote sources required to build a target
\item [do\_generate\_qt\_config\_file] writes a qt.conf file for building a
	Qt-based application
\item [do\_install] copies files from the compilation directory to a holding
	area
\item [do\_install\_ptest\_base] copies the runtime test suite files from the
	compilation directory to a holding area
\item [do\_kernel\_checkout] checks out source/meta branches for a linux-yocto
	style kernel
\item [do\_kernel\_configcheck] validates the kernel configuration for a
	linux-yocto style kernel
\item [do\_kernel\_configme] assembles the kernel configuration for a
	linux-yocto style kernel
\item [do\_kernel\_link\_vmlinux] creates a symbolic link in arch/\$arch/boot
	for vmlinux kernel images
\item [do\_listtasks] lists all defined tasks for a target
\item [do\_menuconfig] runs 'make menuconfig' for the kernel
\item [do\_package] analyzes the content of the holding area and splits it
	into subsets based on available packages and files
\item [do\_package\_index] creates or updates the index in the Package Feed
	area
\item [do\_package\_write] creates the actual packages and places them in the
	Package Feed area
\item [do\_package\_write\_deb] creates the actual DEB packages and places
	them in the Package Feed area
\item [do\_package\_write\_ipk] creates the actual IPK packages and places
	them in the Package Feed area
\item [do\_package\_write\_rpm] creates the actual RPM packages and places
	them in the Package Feed area
\item [do\_package\_write\_tar] creates tar archives for packages and places
	them in the Package Feed area
\item [do\_packagedata] creates package metadata used by the build system to
	generate the final packages
\item [do\_patch] locates patch files and applies them to the source code
\item [do\_populate\_lic] writes license information for the recipe that is
	collected later when the image is constructed
\item [do\_populate\_sdk] creates the file and directory structure for an
	installable SDK
\item [do\_populate\_sysroot] copies a subset of files installed by
	do\_install into the sysroot in order to make them available to other
	recipes
\item [do\_rm\_work] removes work files after the build system has finished
	with them
\item [do\_rm\_work\_all] top-level task for removing work files after the
	build system has finished with them
\item [do\_rootfs] creates the root filesystem (file and directory structure)
	for an image
\item [do\_savedefconfig] creates a minimal Linux kernel configuration file
\item [do\_sizecheck] checks the size of the kernel image against
	KERNEL\_IMAGE\_MAXSIZE (if set)
\item [do\_spdx] a build stage that takes the source code and scans it on a
	remote FOSSOLOGY server in order to produce an SPDX document
\item [do\_strip] strips unneeded sections out of the Linux kernel image
\item [do\_testimage] boots an image and performs runtime tests within the
	image
\item [do\_testimage\_auto] boots an image and performs runtime tests within
	the image immediately after it has been built
\item [do\_uboot\_mkimage] creates a uImage file from the kernel for the
	U-Boot bootloader
\item [do\_unpack] unpacks the source code into a working directory
\item [do\_validate\_branches] ensures that the source/meta branches are on
	the locations specified by their SRCREV values for a linux-yocto style
	kernel"
\item [do\_vmdkimg] creates a .vmdk image for use with VMware and compatible
	virtual machine hosts"
\end{description}
\end{frame}

\begin{frame}
\frametitle{Machines}
machine configs are stored in the layers: conf/machine/*

Settings can be splitted in different include *.inc files. E.g. one include for
CPU that is used by the SoC inc file, that is used by the Board .conf file.

Typically these variables are set in the machine config:
\begin{description}
	\item[SOC\_FAMILY] groups together machines based upon the same family of SOC
		(System On Chip)
	\item [UBOOT\_MACHINE] value passed on the make command line when building a
		U-Boot image
	\item [UBOOT\_MAKE\_TARGET] target called in the Makefile
	\item [UBOOT\_ENTRYPOINT] entry point for the U-Boot image
	\item [PREFERRED\_PROVIDER\_virtual/kernel] default kernel
	\item [KERNEL\_DEVICETREE] default devicetree
	\item [KERNEL\_IMAGETYPE] type of kernel to build for a device,
		defaults to 'zImage'
	\item [MACHINEOVERRIDES] lists overrides specific to the current machine.
		By default, this list includes the value of MACHINE. This can be used in
		recipes; e.g. MACHINEOVERRIDES =. "mymachine" and in the recipe
		SRC\_URI\_append\_mymachine = "file://mymachine-quirk.patch"
	\item [MACHINE\_FEATURES] list of hardware features the MACHINE supports
	\item [MACHINE\_EXTRA\_RRECOMMENDS] list of machine-specific packages to
		install as part of the image being built that are not essential for booting
		the machine. The image being built has no build dependencies on the packages
		in this list.
	\item [SERIAL\_CONSOLE] speed and device for the serial port used to attach
		the serial console. This variable is given to the kernel as the 'console'
		parameter. After booting occurs, getty is started on that port so remote
		login is possible.
	\item [PREFERRED\_VERSION\_xserver-xorg] compatible xserver version
	\item [DEFAULTTUNE] e.g. armv6hf or cortexa8hf-neon, x86-64, \dots
	\item [IMAGE\_FSTYPES] formats for the rootfs, e.g. "ext3 tar.bz2"
	\item [IMAGE\_CLASSES] list of classes that all images should inherit, default
		is image\_types
	\item [TUNE\_FEATURES] e.g. "armv7a vfp neon"
	\item [TUNEVALID] Descriptions, stored as flags, of valid tuning features
	\item [TUNECONFLICTS] list of conflicting features for a given feature
\end{description}
\end{frame}

\begin{frame}
\frametitle{Configuration}
bla
\end{frame}

\begin{frame}
\frametitle{using meta-fsl}
bla
\end{frame}

\begin{frame}
\frametitle{using meta-ti}
bla
\end{frame}

\begin{frame}
\frametitle{commands and debug methods}
bla
\end{frame}

\input{tailpres}