poky: subtree update:c67f57c09e..c6bc20857c
Adrian Freihofer (2):
oe-publish-sdk: fix layers init via ssh
oe-publish-sdk: add --keep-orig option
Alexander Kanavin (68):
meta-selftest: correct the virgl test for 5.8 kernels
bison: upgrade 3.6.4 -> 3.7.1
util-linux: upgrade 2.35.2 -> 2.36
python3-numpy: upgrade 1.19.0 -> 1.19.1
python3-setuptools: upgrade 49.3.1 -> 49.6.0
rsync: upgrade 3.2.2 -> 3.2.3
util-linux: merge .inc into .bb
acpica: upgrade 20200528 -> 20200717
asciidoc: upgrade 9.0.1 -> 9.0.2
cryptodev: upgrade 1.10 -> 1.11
diffoscope: upgrade 153 -> 156
epiphany: upgrade 3.36.3 -> 3.36.4
font-alias: upgrade 1.0.3 -> 1.0.4
gtk+3: upgrade 3.24.21 -> 3.24.22
libcheck: upgrade 0.15.0 -> 0.15.2
libinput: upgrade 1.16.0 -> 1.16.1
libpipeline: upgrade 1.5.2 -> 1.5.3
libx11: upgrade 1.6.9 -> 1.6.11
linux-firmware: upgrade 20200619 -> 20200721
man-pages: upgrade 5.07 -> 5.08
mc: upgrade 4.8.24 -> 4.8.25
mesa: upgrade 20.1.4 -> 20.1.5
piglit: upgrade to latest revision
re2c: upgrade 2.0 -> 2.0.2
sysstat: upgrade 12.2.2 -> 12.4.0
vala: upgrade 0.48.7 -> 0.48.9
bootchart2: update 0.14.8 -> 0.14.9
harfbuzz: convert to meson, enable gobject introspection
pango: update 1.44.7 -> 1.46.0
boost: update 1.73.0 -> 1.74.0
xev: update 1.2.3 -> 1.2.4
wpebackend-fdo: update 1.6.1 -> 1.7.1
gpgme: update 1.13.1 -> 1.14.0
libpsl: update 0.21.0 -> 0.21.1.
gettext: update 0.20.2 -> 0.21
cmake: update 3.17.3 -> 3.18.1
linux-firmware: update 20200721 -> 20200817
meson: update 0.55.0 -> 0.55.1
systemd-boot: bump version to 246.2
json-glib: inherit upstream-version-is-even
packagegroup-core-device-devel: remove
oeqa/x32lib: rework to use readelf from the host
oeqa/multilib: rework to use readelf from the host
oeqa/multilib: un-skip the connman test
poky.conf: do not install packagegroup-core-device-devel into qemu images
glib-2.0: update 2.64.4 -> 2.64.5
cmake: upgrade 3.18.1 -> 3.18.2
libxcrypt: upgrade 4.4.16 -> 4.4.17
debianutils: upgrade 4.11 -> 4.11.1
enchant2: upgrade 2.2.8 -> 2.2.9
harfbuzz: upgrade 2.7.1 -> 2.7.2
libmpc: upgrade 1.1.0 -> 1.2.0
librepo: upgrade 1.12.0 -> 1.12.1
libuv: upgrade 1.38.1 -> 1.39.0
msmtp: upgrade 1.8.11 -> 1.8.12
ninja: upgrade 1.10.0 -> 1.10.1
p11-kit: upgrade 0.23.20 -> 0.23.21
pango: upgrade 1.46.0 -> 1.46.1
re2c: upgrade 2.0.2 -> 2.0.3
resolvconf: upgrade 1.82 -> 1.83
stress-ng: upgrade 0.11.18 -> 0.11.19
gnu-config: update to latest revision
nasm: update 2.15.03 -> 2.15.05
libva-utils: fix upstream version check
gnupg: update 2.2.21 -> 2.2.22
libx11: update 1.6.11 -> 1.6.12
mesa: update 20.1.5 -> 20.1.6
xserver-xorg: update 1.20.8 -> 1.20.9
Andrey Zhizhikin (1):
insane: check for missing update-alternatives inherit
Anibal Limon (1):
recipes-kernel: linux-firmware add qcom-venus-{5.2,5.4} packages
Aníbal Limón (1):
recipes-graphics/xorg-xserver: Add patch to fix segfault when probe
Armin Kuster (2):
bind: update to 9.11.22 ESV
core-image-sato: qemumips use 512 mem
Bruce Ashfield (30):
linux-yocto/5.4: update to v5.4.59
linux-yocto/5.8: update to v5.8.2
yocto-bsp: update to v5.4.56
yocto-bsp: update to v5.4.58
qemu: bump default reference kernel to v5.8
linux-yocto/5.8: fix perf and virtio_scsi warnings
linux-yocto-rt/5.8: fix lttng-modules build
linux-yocto/5.8: selftests/bpf: Prevent runqslower from racing on building bpftool
linux-yocto/5.8: disable CONFIG_NFS_DISABLE_UDP_SUPPORT
poky: set preferred version for linux-yocto to be v5.8
poky-tiny: set preferred version to 5.8
poky: add preferred version for linux-yocto-rt
linux-yocto/5.8: update to v5.8.3
linux-yocto/5.4: update to v5.4.60
kernel: config cleanups for 5.8+
linux-yocto/5.4: update to v5.4.61
linux-yocto/5.8: update to v5.8.4
linux-yocto/5.8: disable IKHEADERS in default builds
kernel-yocto: allow promotion of configuration warnings to errors
kernel-yocto: checksum all modifications to available kernel fragments directories
lttng-modules/devupstream: bump to latest 2.12 commits
linux-yocto-dev: bump to v5.9+
linux-yocto/5.8: update to v5.8.5
kernel-devsrc: account for HOSTCC and HOSTCXX
linux-yocto/config: netfilter: Enable nat for ipv4 and ipv6
linux-yocto/5.8: update to v5.8.8
linux-yocto/5.4: update to v5.4.64
linux-yocto/config: configuration warning cleanup
linux-yocto/5.8: update to v5.8.9
linux-yocto/5.4: update to v5.4.65
Changhyeok Bae (2):
iw: upgrade 5.4 -> 5.8
iputils: upgrade s20190709 -> s20200821
Chris Laplante (12):
bitbake: compat.py: remove file since it no longer actually implements anything
bitbake: COW: formatting
bitbake: COW: migrate test suite into tests/cow
cve-update-db-native: add progress handler
cve-check/cve-update-db-native: use lockfile to fix usage under multiconfig
cve-update-db-native: use context manager for cve_f
cve-check: avoid FileNotFoundError if no do_cve_check task has run
bitbake: utils: process_profilelog: use context manager
bitbake: utils: fix UnboundLocalError when _print_exception raises
cve-update-db-native: be less magical about checking whether the cve-check class is enabled
cve-update-db-native: move -journal checking into do_fetch
cve-update-db-native: remove unused variable
Christophe GUIBOUT (1):
initramfs-framework: support kernel cmdline with double quotes
Denys Dmytriyenko (2):
weston: upgrade 8.0.0 -> 9.0.0
cryptodev: bump 1 commit past 1.11 to fix 5.9-rc1+
Diego Sueiro (2):
license_image.bbclass: Create symlink to the image license manifest dir
license_image.bbclass: Fix symlink to the image license manifest dir creation
Douglas Royds (1):
tcmode-default: Drop gcc-cross-initial, gcc-crosssdk-initial references
Frazer Clews (1):
bitbake: lib: fix most undefined code picked up by pylint
Geoff Parker (1):
systemd-serialgetty: Replace sed quoting using ' with " to allow var expansion
Jacob Kroon (1):
gcc10: Don't default back to -fcommon
Jean-Francois Dagenais (1):
bitbake: siggen: clean_basepath: remove recipe full path when virtual:xyz present
Jens Rehsack (1):
lttng-modules: backport patches from 2.12.x to fix 5.4.64+ and 5.8.9+ builds
Joe Slater (1):
pseudo: fix renaming to self
Jon Mason (4):
cortex-m0plus.inc: change file permissions
tune-cortexa55.inc: clean-up ARMv8.2a uses
tune-cortexa57-cortexa53.inc: add CRC and set march
tune-cortexa*: Cleanups
Joshua Watt (8):
wic: Add 512 Byte alignment to --offset
oeqa: runtime_tests: Extra GPG debugging
oeqa: sdk: Capture stderr output
oeqa: reproducible: Fix test not producing diffs
diffoscope: upgrade 156 -> 158
bitbake: bitbake: Add parsing torture test
bitbake: cooker: Block SIGINT in worker processes
sphinx: dev-manual: Clarify that virtual providers do not apply to runtime dependencies
Kai Kang (1):
dhcpcd: 9.1.4 -> 9.2.0
Kevin Hao (1):
meta-yocto-bsp: Bump to the v5.8 kernel
Khairul Rohaizzat Jamaluddin (1):
wic/bootimg-efi: IMAGE_EFI_BOOT_FILES variable added to separate bootimg-efi and bootimg-partition
Khem Raj (24):
gcc-cross-canadian: Install gcc/g++ wrappers for musl
uninative: Upgrade to 2.9
packagegroup-core-tools-profile: Disable lttng-modules for riscv64
lttng-modules: Disable on riscv64
kexec-tools: Fix build with -fno-common on ppc
lttng-tools: Do not build for riscv64
util-linux: Allow update alternatives for additional apps
lttng-tools: lttng-ust works on riscv64
json-glib: Backport a build fix with clang
rpcbind: Use update-alternatives for rpcinfo
go: Upgrade to 1.15 major release
weston-init: Redefine weston service and add socket activation option
musl: Upgrade to latest master
libucontext: Recognise riscv32 architecture
linuxloader.bbclass: Define riscv32 ldso for musl
populate_sdk_ext: Do not assume local.conf will always exist
weston: plane_add_prop() calls break musl atomic modesetting
weston-init: Enable RDP screen share
weston-init: Do not use fbdev backend
weston-init: Select drm/fbdev backends for qemu machines
oeqa/weston: Fix tests to run with systemd
core-image-weston: Bump qemu memory to 512M
go: Update to 1.15.2 minor release
bind: Inherit update-alternatives
Mark Hatle (6):
package_tar.bbclass: Sync to the other package_* classes
kernel.bbclass: Remove do_install[prefunc] no longer needed
buildhistory.bbclass: Rework to use read_subpackage_metadata
kernel.bbclass: Move away from calling package_get_auto_pr
package.bbclass: hash equivalency and pr service
bitbake: process.py: Handle SystemExit exception to eliminate backtrace
Mark Morton (1):
sphinx: test-manual code block, link, and format update
Martin Jansa (7):
devtool: expand SRC_URI when guessing recipe update mode
image-artifact-names: introduce new bbclass and move some variables into it
kernel.bbclass: use bash variables like imageType, base_name without {}
kernel.bbclass: eliminate (initramfs_)symlink_name variables
kernel.bbclass: use camelCase notation for bash variables in do_deploy
*-initramfs: don't use .rootfs IMAGE_NAME_SUFFIX
bitbake.conf: use ${TCMODE}-${TCLIBC} directory for CACHE
Matt Madison (1):
image.bbclass: fix REPRODUCIBLE_TIMESTAMP_ROOTFS reference
Michael Gloff (2):
sysvinit rc: Use PSPLASH_FIFO_DIR for progress fifo
sysvinit: Remove ${B} assignment
Michael Tretter (1):
devtool: deploy-target: Fix size calculation for hard links
Ming Liu (2):
systemd: split systemd specific udev rules into its own package
libubootenv: inherit uboot-config
Mingli Yu (3):
qemu: always define unknown_lock_type
qemu: override DEBUG_BUILD
bison: remove the parallel build patch
Naveen Saini (1):
lib/oe/recipeutils.py: add support for BBFILES_DYNAMIC
Nicolas Dechesne (73):
linux-libc-headers: kernel headers are installed in STAGING_KERNEL_BUILDDIR
bitbake: sphinx: add initial build infrastructure
bitbake: sphinx: initial sphinx support
bitbake: sphinx: bitbake-user-manual: use builtin sphinx glossary
bitbake: sphinx: switch to readthedocs theme
bitbake: sphinx: override theme CSS
bitbake: sphinx: fixup for links
bitbake: sphinx: fix links inside notes
bitbake: sphinx: fixes all remaining warnings
bitbake: sphinx: Makefile.sphinx: add clean and publish targets
bitbake: sphinx: tweak html output a bit
bitbake: sphinx: add SPDX headers
bitbake: sphinx: index: move the boilerplate at the end of the page
bitbake: sphinx: conf: enable extlinks extension
bitbake: sphinx: add releases page
bitbake: sphinx: bitbake-user-manual: insert additional blank line after title
bitbake: sphinx: last manual round of fixes/improvements
bitbake: sphinx: update style for important, caution and warnings
bitbake: sphinx: remove leading '/'
bitbake: sphinx: theme_override: properly set font for verbatim text
bitbake: bitbake-user-manual: fix bad links
sphinx: add initial build infrastructure
sphinx: initial sphinx support
sphinx: ref-variables: use builtin sphinx glossary
sphinx: overview-manual: add figures
sphinx: switch to readthedocs theme
sphinx: Add SPDX license headers
sphinx: add CSS theme override
sphinx: bsp-guide: add figures
sphinx: add Yocto project logo
sphinx: conf: update copyright
sphinx: conf: add substitutions/global variables
sphinx: add boilerplate file
sphinx: add boilerplate to manuals
sphinx: ref-manual: add revision history table
sphinx: add a general index
sphinx: conf.py: enable sphinx.ext.autosectionlabel
sphinx: ref-manual: use builtin glossary for the Terms section
sphinx: fix internal links
sphinx: ref-manual: fix typo
sphinx: fix custom term links
sphinx: manual updates for some links
sphinx: dev-manual add figures
sphinx: kernel-dev: add figures
sphinx: profile-manual: add figures
sphinx: fix up bold text for informalexample container
sphinx: ref-manual: add figures
sphinx: sdk-manual: add figures
sphinx: test-manual: add figures
sphinx: toaster-manual: add figures
sphinx: add links for Yocto project website
sphinx: fix links when the link text should be displayed
sphinx: add links to terms in the BitBake glossary
sphinx: add links to section in the Bitbake manual
sphinx: setup extlink for docs.yoctoproject.org
sphinx: enable intersphinx extension
sphinx: insert blank below between title and toc
sphinx: fix up terms related to kernel-fitimage
sphinx: conf: a few rendering tweaks
sphinx: makefile: add publish target
sphinx: conf: include CSS/JS files, the proper way
sphinx: convert 'what I wish I'd known'
sphinx: convert 'transitioning to a custom environment'
sphinx: ref-manual: fix heading for oe-init-build-env
sphinx: brief-yoctoprojectqs: fix up all remaining rendering issues
sphinx: Makefile.sphinx improvements
sphinx: convert bsp-guide
sphinx: remove leading '/'
sphinx: update style for important, caution and warnings
sphinx: profile-manual: convert profile-manual
sphinx: theme_override: properly set font for verbatim text
sphinx: theme_override: add tying-it-together admonition
sphinx: conf: exclude adt-manual/*.rst
Oleksandr Kravchuk (1):
ell: update to 0.33
Ovidiu Panait (1):
libxml2: Fix CVE-2020-24977
Peter A. Bigot (2):
bluez5: fix builds that require ell support
timezone: include leap second data in tzdata-core
Peter Bergin (1):
systemd: avoid failing if no udev rules provided
Pierre-Jean Texier (2):
libubootenv: upgrade 0.3 -> 0.3.1
diffoscope: upgrade 158 -> 160
Quentin Schulz (16):
sphinx: brief-yoctoprojectqs: remove redundant welcome
sphinx: brief-yoctoprojectqs: fix ambiguous note for cyclone5 example
sphinx: brief-yoctoprojectqs: add missing boilerplate
sphinx: overview-manual: add link to AUH how-to section
sphinx: overview-manual: fix bitbake basic explanation
sphinx: brief-yoctoprojectqs: add note on branch consistency between layers
sphinx: what-i-wish-id-known: update "don't be fooled by doc search results"
sphinx: overview-manual: remove highlight in bold section
sphinx: replace special quotes with single and double quotes
sphinx: fix incorrect indentations
sphinx: brief-yoctoprojectqs: put other distros note after Ubuntu-specific packages
sphinx: fix a few typos or missing/too many words
sphinx: "highlight" some variables, tasks or files
sphinx: fix or add missing links and remove mention of Eclipse workflow
ref-manual: examples: hello-autotools: upgrade to 2.10
ref-manual: examples: libxpm: add relative path to .inc
Rahul Kumar (1):
systemd-serialgetty: Fix sed expression quoting
Rasmus Villemoes (1):
kernel.bbclass: run do_symlink_kernsrc before do_patch
Richard Purdie (74):
nativesdk-sdk-provides-dummy: Add /bin/sh
bitbake: fetch2/wget: Remove buffering parameter
bitbake: cooker: Ensure parse_quit thread is closed down
bitbake: cooker: Explictly shut down the sync thread
bitbake: fetch2: Drop cups.org from wget status checks
bitbake: build/msg: Cleanup verbose option handling
bitbake: cooker/cookerdata/main: Improve loglevel handling
bitbake: cookerdata: Ensure UI options are updated to the server
bitbake: cooker/cookerdata: Ensure UI event log is updated from commandline
bitbake: cooker: Defer configuration init to after UI connection
bitbake: server/process: Move the socket code to server process only
bitbake: main/server/process: Drop configuration object passing
bitbake: cooker: Ensure BB_ORIGENV is updated by changes to configuration.env
bitbake: server/process: Log extra threads at exit
bitbake: server/process: Add bitbake-server and exec() a new server process
bitbake: runqueue: Don't use sys.argv
bitbake: cooker: Ensure cooker's enviroment is updated on updateConfig
connman-gnome/matchbox-desktop: Remove file:// globbing
selftest/recipetool: Drop globbing SRC_URI test, no longer supported
local.conf.sample: Document memory resident bitbake
bitbake: fetch2: Drop globbing supprt in file:// SRC_URIs
bitbake: server/process: Use sys.executable for bitbake-server
bitbake: process: Avoid bb.utils.timeout
bitbake: utils: Drop broken timeout function
bitbake: server/process: Fix typo in code causing tracebacks
oeqa/selftest: Apply patch to fix cpio build with -fno-common
runqemu: Show an error for conflicting graphics options
lttng: Move platform logic to dedicated inc file
patchelf: upgrade 0.11 -> 0.12
build-appliance/packagegroup-core-base-utils: Replace dhcp-client/dhcp-server with dhcpcd/kea
selftest/prservice: Improve test failure message
iputils: Adapt ${PN}-tftpd package dependency to PACKAGECONFIG
bitbake: process/knotty: Improve early exception handling
bitbake: cooker/cookerdata: Use BBHandledException, not sys.exit()
bitbake: cookerdata: Fix exception raise statements
bitbake: process: Avoid printing binary strings for leftover processes
bitbake: server/process: Ensure logging is flushed
bitbake: server/process: Don't show tracebacks if the lockfile is removed
bitbake: cooker: Ensure parser replacement calls parser final_cleanup
bitbake: cooker: Assign a name to the sync thread to aid debugging
bitbake: server/process: Ensure we don't keep looping if some other server is started
bitbake: server/process: Prefix the log data with pid/time information
bitbake: server/process: Note when commands complete in logs
bitbake: cooker: Ensure parser is cleaned up
runqemu: Add a hook to allow it to renice
bitbake: cooker: Avoid parser deadlocks
bitbake: cooker: Ensure parser worker signal handlers are default
selftest/signing: Ensure build path relocation is safe
oeqa/concurrencytest: Improve builddir path manipulations
bitbake: cooker/command: Fix disconnection handling
bitbake: tinfoil: Ensure sockets don't leak even when exceptions occur
bitbake: tests/fetch: Move away from problematic freedesktop.org urls
bitbake: sphinx: Enhance the sphinx experience/nagivation with:
bitbake: sphinx: theme_override: Use bold for emphasis text
Revert "qemu: always define unknown_lock_type"
Revert "core-image-sato: qemumips use 512 mem"
sphinx: Organize top level docs
sphinx: releases.rst: Add index/links to docs for previous releases
sphinx: boilerplate.rst: Drop versions notes as we have better navigation now
sphinx: boilerplate.rst: Sphinx puts the copyright elsewhere
sphinx: history: Move revision history to its own section
sphinx: manuals: Move boilerplate after toctree
sphinx: Add support for multiple docs version
sphinx: index.rst: Fix links
sphinx: ref-system-requirements: Improve formatting of the notes sections, merging them
sphinx: ref-manual links fixes and many other cleanups to import
sphinx: dev-manual: Various URL, code block and other fixes to imported data
sphinx: sdk-manual: Various URL, code block and other fixes to imported data
sphinx: kernel-dev: Various URL, code block and other fixes to imported data
sphinx: theme_override: Use bold for emphasis text
sphinx: ref-tasks: Add populate_sdk_ext task definition
sphinx: ref-manual/migration: Split each release into its own file
sphinx: overview-manual: Various URL, code block and other fixes to imported data
build-appliance-image: Update to master head revision
Robert Yang (3):
bitbake: cooker.py: Save prioritized BBFILES to BBFILES_PRIORITIZED
bitbake: utils.py: get_file_layer(): Exit the loop when file is matched
bitbake: utils.py: get_file_layer(): Improve performance
Ross Burton (25):
package.bbclass: explode the RPROVIDES so we don't think the versions are provides
elfutils: silence a new QA warning
insane: improve gnu-hash-style warning
gdk-pixbuf: add tests PACKAGECONFIG
debianutils: change SRC_URI to use snapshot.debian.org
insane: only load real files as ELF
autoconf: consolidate SRC_URI
autoconf: consolidate DEPENDS
kea: no need to depend on kea-native
kea: don't use PACKAGECONFIG inappropriately
kea: bump to 1.7.10
help2man: rewrite recipe
local.conf.sample.extended: remove help2man reference
curl: add vendors to CVE_PRODUCT to exclude false positives
harfbuzz: update patch status
harfbuzz: fix a build race around hb-version.h
cmake: whitelist CVE-2016-10642
ncurses: remove config.cache
qemu: fix CVE-2020-14364
cve-update-db-native: remove unused import
cve-update-db-native: add more logging when fetching
cve-update-db-native: use fetch task
alsa-plugins: improve .la removal
sato-screenshot: improve .la removal
buildhistory-diff: use BUILDDIR to know where buildhistory is
Saul Wold (1):
gnupg: uprev 2.2.22 -> 2.2.23
Stacy Gaikovaia (2):
bison: uprev from 3.7.1 to 3.7.2
valgrind: fix memcheck vgtests remove fullpath-after flags
Steve Sakoman (1):
xinput-calibrator: change SRC_URI to branch with libinput support
Sumit Garg (1):
insane: fix gnu-hash-style check
TeohJayShen (1):
oeqa/runtime: add test for matchbox-terminal
Tim Orling (1):
sphinx: toaster-manual: fix vars, links, code blocks
Vijai Kumar K (2):
image_types_wic: Add ASSUME_PROVIDED to WICVARS
wic: misc: Add /bin to the list of searchpaths
Yanfei Xu (1):
kernel-yocto: only replace leading -I in include paths
Yi Zhao (1):
glib-networking: add ptest
Zhixiong Chi (1):
gnutls: CVE-2020-24659
akuster (8):
log4cplus: move meta-oe pkg to core
kea: Move from meta-networking
maintainers.inc: Add me as kea & log4plus maintainer.
dhcpcd: Move from meta-network as OE-Core needs a client
maintainers.inc: Add me as dhcpcd maintainer
dhcp: remove from core
bind: Add 9.16.x
bind: 9.11 remove
hongxu (1):
sysstat: fix installed-vs-shipped QA Issue in systemd
zangrc (4):
libcap:upgrade 2.42 -> 2.43
libcap-ng:upgrade 0.7.10 -> 0.7.11
libgpg-error:upgrade 1.38 -> 1.39
at-spi2-core:upgrade 2.36.0 -> 2.36.1
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I5542f5eea751a2641342e945725fd687cd74bebe
diff --git a/poky/bitbake/doc/bitbake-user-manual/bitbake-user-manual-execution.rst b/poky/bitbake/doc/bitbake-user-manual/bitbake-user-manual-execution.rst
new file mode 100644
index 0000000..019afd2
--- /dev/null
+++ b/poky/bitbake/doc/bitbake-user-manual/bitbake-user-manual-execution.rst
@@ -0,0 +1,733 @@
+.. SPDX-License-Identifier: CC-BY-2.5
+
+=========
+Execution
+=========
+
+|
+
+The primary purpose for running BitBake is to produce some kind of
+output such as a single installable package, a kernel, a software
+development kit, or even a full, board-specific bootable Linux image,
+complete with bootloader, kernel, and root filesystem. Of course, you
+can execute the ``bitbake`` command with options that cause it to
+execute single tasks, compile single recipe files, capture or clear
+data, or simply return information about the execution environment.
+
+This chapter describes BitBake's execution process from start to finish
+when you use it to create an image. The execution process is launched
+using the following command form: ::
+
+ $ bitbake target
+
+For information on
+the BitBake command and its options, see ":ref:`The BitBake Command
+<bitbake-user-manual-command>`" section.
+
+.. note::
+
+ Prior to executing BitBake, you should take advantage of available
+ parallel thread execution on your build host by setting the
+ :term:`BB_NUMBER_THREADS` variable in
+ your project's ``local.conf`` configuration file.
+
+ A common method to determine this value for your build host is to run
+ the following: ::
+
+ $ grep processor /proc/cpuinfo
+
+ This command returns
+ the number of processors, which takes into account hyper-threading.
+ Thus, a quad-core build host with hyper-threading most likely shows
+ eight processors, which is the value you would then assign to
+ ``BB_NUMBER_THREADS``.
+
+ A possibly simpler solution is that some Linux distributions (e.g.
+ Debian and Ubuntu) provide the ``ncpus`` command.
+
+Parsing the Base Configuration Metadata
+=======================================
+
+The first thing BitBake does is parse base configuration metadata. Base
+configuration metadata consists of your project's ``bblayers.conf`` file
+to determine what layers BitBake needs to recognize, all necessary
+``layer.conf`` files (one from each layer), and ``bitbake.conf``. The
+data itself is of various types:
+
+- **Recipes:** Details about particular pieces of software.
+
+- **Class Data:** An abstraction of common build information (e.g. how to
+ build a Linux kernel).
+
+- **Configuration Data:** Machine-specific settings, policy decisions,
+ and so forth. Configuration data acts as the glue to bind everything
+ together.
+
+The ``layer.conf`` files are used to construct key variables such as
+:term:`BBPATH` and :term:`BBFILES`.
+``BBPATH`` is used to search for configuration and class files under the
+``conf`` and ``classes`` directories, respectively. ``BBFILES`` is used
+to locate both recipe and recipe append files (``.bb`` and
+``.bbappend``). If there is no ``bblayers.conf`` file, it is assumed the
+user has set the ``BBPATH`` and ``BBFILES`` directly in the environment.
+
+Next, the ``bitbake.conf`` file is located using the ``BBPATH`` variable
+that was just constructed. The ``bitbake.conf`` file may also include
+other configuration files using the ``include`` or ``require``
+directives.
+
+Prior to parsing configuration files, BitBake looks at certain
+variables, including:
+
+- :term:`BB_ENV_WHITELIST`
+- :term:`BB_ENV_EXTRAWHITE`
+- :term:`BB_PRESERVE_ENV`
+- :term:`BB_ORIGENV`
+- :term:`BITBAKE_UI`
+
+The first four variables in this list relate to how BitBake treats shell
+environment variables during task execution. By default, BitBake cleans
+the environment variables and provides tight control over the shell
+execution environment. However, through the use of these first four
+variables, you can apply your control regarding the environment
+variables allowed to be used by BitBake in the shell during execution of
+tasks. See the
+":ref:`bitbake-user-manual/bitbake-user-manual-metadata:Passing Information Into the Build Task Environment`"
+section and the information about these variables in the variable
+glossary for more information on how they work and on how to use them.
+
+The base configuration metadata is global and therefore affects all
+recipes and tasks that are executed.
+
+BitBake first searches the current working directory for an optional
+``conf/bblayers.conf`` configuration file. This file is expected to
+contain a :term:`BBLAYERS` variable that is a
+space-delimited list of 'layer' directories. Recall that if BitBake
+cannot find a ``bblayers.conf`` file, then it is assumed the user has
+set the ``BBPATH`` and ``BBFILES`` variables directly in the
+environment.
+
+For each directory (layer) in this list, a ``conf/layer.conf`` file is
+located and parsed with the :term:`LAYERDIR` variable
+being set to the directory where the layer was found. The idea is these
+files automatically set up :term:`BBPATH` and other
+variables correctly for a given build directory.
+
+BitBake then expects to find the ``conf/bitbake.conf`` file somewhere in
+the user-specified ``BBPATH``. That configuration file generally has
+include directives to pull in any other metadata such as files specific
+to the architecture, the machine, the local environment, and so forth.
+
+Only variable definitions and include directives are allowed in BitBake
+``.conf`` files. Some variables directly influence BitBake's behavior.
+These variables might have been set from the environment depending on
+the environment variables previously mentioned or set in the
+configuration files. The ":ref:`bitbake-user-manual/bitbake-user-manual-ref-variables:Variables Glossary`"
+chapter presents a full list of
+variables.
+
+After parsing configuration files, BitBake uses its rudimentary
+inheritance mechanism, which is through class files, to inherit some
+standard classes. BitBake parses a class when the inherit directive
+responsible for getting that class is encountered.
+
+The ``base.bbclass`` file is always included. Other classes that are
+specified in the configuration using the
+:term:`INHERIT` variable are also included. BitBake
+searches for class files in a ``classes`` subdirectory under the paths
+in ``BBPATH`` in the same way as configuration files.
+
+A good way to get an idea of the configuration files and the class files
+used in your execution environment is to run the following BitBake
+command: ::
+
+ $ bitbake -e > mybb.log
+
+Examining the top of the ``mybb.log``
+shows you the many configuration files and class files used in your
+execution environment.
+
+.. note::
+
+ You need to be aware of how BitBake parses curly braces. If a recipe
+ uses a closing curly brace within the function and the character has
+ no leading spaces, BitBake produces a parsing error. If you use a
+ pair of curly braces in a shell function, the closing curly brace
+ must not be located at the start of the line without leading spaces.
+
+ Here is an example that causes BitBake to produce a parsing error: ::
+
+ fakeroot create_shar() {
+ cat << "EOF" > ${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.sh
+ usage()
+ {
+ echo "test"
+ ###### The following "}" at the start of the line causes a parsing error ######
+ }
+ EOF
+ }
+
+ Writing the recipe this way avoids the error:
+ fakeroot create_shar() {
+ cat << "EOF" > ${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.sh
+ usage()
+ {
+ echo "test"
+ ###### The following "}" with a leading space at the start of the line avoids the error ######
+ }
+ EOF
+ }
+
+Locating and Parsing Recipes
+============================
+
+During the configuration phase, BitBake will have set
+:term:`BBFILES`. BitBake now uses it to construct a
+list of recipes to parse, along with any append files (``.bbappend``) to
+apply. ``BBFILES`` is a space-separated list of available files and
+supports wildcards. An example would be: ::
+
+ BBFILES = "/path/to/bbfiles/*.bb /path/to/appends/*.bbappend"
+
+BitBake parses each
+recipe and append file located with ``BBFILES`` and stores the values of
+various variables into the datastore.
+
+.. note::
+
+ Append files are applied in the order they are encountered in BBFILES.
+
+For each file, a fresh copy of the base configuration is made, then the
+recipe is parsed line by line. Any inherit statements cause BitBake to
+find and then parse class files (``.bbclass``) using
+:term:`BBPATH` as the search path. Finally, BitBake
+parses in order any append files found in ``BBFILES``.
+
+One common convention is to use the recipe filename to define pieces of
+metadata. For example, in ``bitbake.conf`` the recipe name and version
+are used to set the variables :term:`PN` and
+:term:`PV`: ::
+
+ PN = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE', False),d)[0] or 'defaultpkgname'}"
+ PV = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE', False),d)[1] or '1.0'}"
+
+In this example, a recipe called "something_1.2.3.bb" would set
+``PN`` to "something" and ``PV`` to "1.2.3".
+
+By the time parsing is complete for a recipe, BitBake has a list of
+tasks that the recipe defines and a set of data consisting of keys and
+values as well as dependency information about the tasks.
+
+BitBake does not need all of this information. It only needs a small
+subset of the information to make decisions about the recipe.
+Consequently, BitBake caches the values in which it is interested and
+does not store the rest of the information. Experience has shown it is
+faster to re-parse the metadata than to try and write it out to the disk
+and then reload it.
+
+Where possible, subsequent BitBake commands reuse this cache of recipe
+information. The validity of this cache is determined by first computing
+a checksum of the base configuration data (see
+:term:`BB_HASHCONFIG_WHITELIST`) and
+then checking if the checksum matches. If that checksum matches what is
+in the cache and the recipe and class files have not changed, BitBake is
+able to use the cache. BitBake then reloads the cached information about
+the recipe instead of reparsing it from scratch.
+
+Recipe file collections exist to allow the user to have multiple
+repositories of ``.bb`` files that contain the same exact package. For
+example, one could easily use them to make one's own local copy of an
+upstream repository, but with custom modifications that one does not
+want upstream. Here is an example: ::
+
+ BBFILES = "/stuff/openembedded/*/*.bb /stuff/openembedded.modified/*/*.bb"
+ BBFILE_COLLECTIONS = "upstream local"
+ BBFILE_PATTERN_upstream = "^/stuff/openembedded/"
+ BBFILE_PATTERN_local = "^/stuff/openembedded.modified/"
+ BBFILE_PRIORITY_upstream = "5" BBFILE_PRIORITY_local = "10"
+
+.. note::
+
+ The layers mechanism is now the preferred method of collecting code.
+ While the collections code remains, its main use is to set layer
+ priorities and to deal with overlap (conflicts) between layers.
+
+.. _bb-bitbake-providers:
+
+Providers
+=========
+
+Assuming BitBake has been instructed to execute a target and that all
+the recipe files have been parsed, BitBake starts to figure out how to
+build the target. BitBake looks through the ``PROVIDES`` list for each
+of the recipes. A ``PROVIDES`` list is the list of names by which the
+recipe can be known. Each recipe's ``PROVIDES`` list is created
+implicitly through the recipe's :term:`PN` variable and
+explicitly through the recipe's :term:`PROVIDES`
+variable, which is optional.
+
+When a recipe uses ``PROVIDES``, that recipe's functionality can be
+found under an alternative name or names other than the implicit ``PN``
+name. As an example, suppose a recipe named ``keyboard_1.0.bb``
+contained the following: ::
+
+ PROVIDES += "fullkeyboard"
+
+The ``PROVIDES``
+list for this recipe becomes "keyboard", which is implicit, and
+"fullkeyboard", which is explicit. Consequently, the functionality found
+in ``keyboard_1.0.bb`` can be found under two different names.
+
+.. _bb-bitbake-preferences:
+
+Preferences
+===========
+
+The ``PROVIDES`` list is only part of the solution for figuring out a
+target's recipes. Because targets might have multiple providers, BitBake
+needs to prioritize providers by determining provider preferences.
+
+A common example in which a target has multiple providers is
+"virtual/kernel", which is on the ``PROVIDES`` list for each kernel
+recipe. Each machine often selects the best kernel provider by using a
+line similar to the following in the machine configuration file: ::
+
+ PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
+
+The default :term:`PREFERRED_PROVIDER` is the provider
+with the same name as the target. BitBake iterates through each target
+it needs to build and resolves them and their dependencies using this
+process.
+
+Understanding how providers are chosen is made complicated by the fact
+that multiple versions might exist for a given provider. BitBake
+defaults to the highest version of a provider. Version comparisons are
+made using the same method as Debian. You can use the
+:term:`PREFERRED_VERSION` variable to
+specify a particular version. You can influence the order by using the
+:term:`DEFAULT_PREFERENCE` variable.
+
+By default, files have a preference of "0". Setting
+``DEFAULT_PREFERENCE`` to "-1" makes the recipe unlikely to be used
+unless it is explicitly referenced. Setting ``DEFAULT_PREFERENCE`` to
+"1" makes it likely the recipe is used. ``PREFERRED_VERSION`` overrides
+any ``DEFAULT_PREFERENCE`` setting. ``DEFAULT_PREFERENCE`` is often used
+to mark newer and more experimental recipe versions until they have
+undergone sufficient testing to be considered stable.
+
+When there are multiple “versions” of a given recipe, BitBake defaults
+to selecting the most recent version, unless otherwise specified. If the
+recipe in question has a
+:term:`DEFAULT_PREFERENCE` set lower than
+the other recipes (default is 0), then it will not be selected. This
+allows the person or persons maintaining the repository of recipe files
+to specify their preference for the default selected version.
+Additionally, the user can specify their preferred version.
+
+If the first recipe is named ``a_1.1.bb``, then the
+:term:`PN` variable will be set to “a”, and the
+:term:`PV` variable will be set to 1.1.
+
+Thus, if a recipe named ``a_1.2.bb`` exists, BitBake will choose 1.2 by
+default. However, if you define the following variable in a ``.conf``
+file that BitBake parses, you can change that preference: ::
+
+ PREFERRED_VERSION_a = "1.1"
+
+.. note::
+
+ It is common for a recipe to provide two versions -- a stable,
+ numbered (and preferred) version, and a version that is automatically
+ checked out from a source code repository that is considered more
+ "bleeding edge" but can be selected only explicitly.
+
+ For example, in the OpenEmbedded codebase, there is a standard,
+ versioned recipe file for BusyBox, ``busybox_1.22.1.bb``, but there
+ is also a Git-based version, ``busybox_git.bb``, which explicitly
+ contains the line ::
+
+ DEFAULT_PREFERENCE = "-1"
+
+ to ensure that the
+ numbered, stable version is always preferred unless the developer
+ selects otherwise.
+
+.. _bb-bitbake-dependencies:
+
+Dependencies
+============
+
+Each target BitBake builds consists of multiple tasks such as ``fetch``,
+``unpack``, ``patch``, ``configure``, and ``compile``. For best
+performance on multi-core systems, BitBake considers each task as an
+independent entity with its own set of dependencies.
+
+Dependencies are defined through several variables. You can find
+information about variables BitBake uses in the
+:doc:`bitbake-user-manual-ref-variables` near the end of this manual. At a
+basic level, it is sufficient to know that BitBake uses the
+:term:`DEPENDS` and
+:term:`RDEPENDS` variables when calculating
+dependencies.
+
+For more information on how BitBake handles dependencies, see the
+:ref:`bitbake-user-manual/bitbake-user-manual-metadata:Dependencies`
+section.
+
+.. _ref-bitbake-tasklist:
+
+The Task List
+=============
+
+Based on the generated list of providers and the dependency information,
+BitBake can now calculate exactly what tasks it needs to run and in what
+order it needs to run them. The
+:ref:`bitbake-user-manual/bitbake-user-manual-execution:executing tasks`
+section has more information on how BitBake chooses which task to
+execute next.
+
+The build now starts with BitBake forking off threads up to the limit
+set in the :term:`BB_NUMBER_THREADS`
+variable. BitBake continues to fork threads as long as there are tasks
+ready to run, those tasks have all their dependencies met, and the
+thread threshold has not been exceeded.
+
+It is worth noting that you can greatly speed up the build time by
+properly setting the ``BB_NUMBER_THREADS`` variable.
+
+As each task completes, a timestamp is written to the directory
+specified by the :term:`STAMP` variable. On subsequent
+runs, BitBake looks in the build directory within ``tmp/stamps`` and
+does not rerun tasks that are already completed unless a timestamp is
+found to be invalid. Currently, invalid timestamps are only considered
+on a per recipe file basis. So, for example, if the configure stamp has
+a timestamp greater than the compile timestamp for a given target, then
+the compile task would rerun. Running the compile task again, however,
+has no effect on other providers that depend on that target.
+
+The exact format of the stamps is partly configurable. In modern
+versions of BitBake, a hash is appended to the stamp so that if the
+configuration changes, the stamp becomes invalid and the task is
+automatically rerun. This hash, or signature used, is governed by the
+signature policy that is configured (see the
+:ref:`bitbake-user-manual/bitbake-user-manual-execution:checksums (signatures)`
+section for information). It is also
+possible to append extra metadata to the stamp using the
+``[stamp-extra-info]`` task flag. For example, OpenEmbedded uses this
+flag to make some tasks machine-specific.
+
+.. note::
+
+ Some tasks are marked as "nostamp" tasks. No timestamp file is
+ created when these tasks are run. Consequently, "nostamp" tasks are
+ always rerun.
+
+For more information on tasks, see the
+:ref:`bitbake-user-manual/bitbake-user-manual-metadata:tasks` section.
+
+Executing Tasks
+===============
+
+Tasks can be either a shell task or a Python task. For shell tasks,
+BitBake writes a shell script to
+``${``\ :term:`T`\ ``}/run.do_taskname.pid`` and then
+executes the script. The generated shell script contains all the
+exported variables, and the shell functions with all variables expanded.
+Output from the shell script goes to the file
+``${T}/log.do_taskname.pid``. Looking at the expanded shell functions in
+the run file and the output in the log files is a useful debugging
+technique.
+
+For Python tasks, BitBake executes the task internally and logs
+information to the controlling terminal. Future versions of BitBake will
+write the functions to files similar to the way shell tasks are handled.
+Logging will be handled in a way similar to shell tasks as well.
+
+The order in which BitBake runs the tasks is controlled by its task
+scheduler. It is possible to configure the scheduler and define custom
+implementations for specific use cases. For more information, see these
+variables that control the behavior:
+
+- :term:`BB_SCHEDULER`
+
+- :term:`BB_SCHEDULERS`
+
+It is possible to have functions run before and after a task's main
+function. This is done using the ``[prefuncs]`` and ``[postfuncs]``
+flags of the task that lists the functions to run.
+
+.. _checksums:
+
+Checksums (Signatures)
+======================
+
+A checksum is a unique signature of a task's inputs. The signature of a
+task can be used to determine if a task needs to be run. Because it is a
+change in a task's inputs that triggers running the task, BitBake needs
+to detect all the inputs to a given task. For shell tasks, this turns
+out to be fairly easy because BitBake generates a "run" shell script for
+each task and it is possible to create a checksum that gives you a good
+idea of when the task's data changes.
+
+To complicate the problem, some things should not be included in the
+checksum. First, there is the actual specific build path of a given task
+- the working directory. It does not matter if the working directory
+changes because it should not affect the output for target packages. The
+simplistic approach for excluding the working directory is to set it to
+some fixed value and create the checksum for the "run" script. BitBake
+goes one step better and uses the
+:term:`BB_HASHBASE_WHITELIST` variable
+to define a list of variables that should never be included when
+generating the signatures.
+
+Another problem results from the "run" scripts containing functions that
+might or might not get called. The incremental build solution contains
+code that figures out dependencies between shell functions. This code is
+used to prune the "run" scripts down to the minimum set, thereby
+alleviating this problem and making the "run" scripts much more readable
+as a bonus.
+
+So far we have solutions for shell scripts. What about Python tasks? The
+same approach applies even though these tasks are more difficult. The
+process needs to figure out what variables a Python function accesses
+and what functions it calls. Again, the incremental build solution
+contains code that first figures out the variable and function
+dependencies, and then creates a checksum for the data used as the input
+to the task.
+
+Like the working directory case, situations exist where dependencies
+should be ignored. For these cases, you can instruct the build process
+to ignore a dependency by using a line like the following: ::
+
+ PACKAGE_ARCHS[vardepsexclude] = "MACHINE"
+
+This example ensures that the
+``PACKAGE_ARCHS`` variable does not depend on the value of ``MACHINE``,
+even if it does reference it.
+
+Equally, there are cases where we need to add dependencies BitBake is
+not able to find. You can accomplish this by using a line like the
+following: ::
+
+ PACKAGE_ARCHS[vardeps] = "MACHINE"
+
+This example explicitly
+adds the ``MACHINE`` variable as a dependency for ``PACKAGE_ARCHS``.
+
+Consider a case with in-line Python, for example, where BitBake is not
+able to figure out dependencies. When running in debug mode (i.e. using
+``-DDD``), BitBake produces output when it discovers something for which
+it cannot figure out dependencies.
+
+Thus far, this section has limited discussion to the direct inputs into
+a task. Information based on direct inputs is referred to as the
+"basehash" in the code. However, there is still the question of a task's
+indirect inputs - the things that were already built and present in the
+build directory. The checksum (or signature) for a particular task needs
+to add the hashes of all the tasks on which the particular task depends.
+Choosing which dependencies to add is a policy decision. However, the
+effect is to generate a master checksum that combines the basehash and
+the hashes of the task's dependencies.
+
+At the code level, there are a variety of ways both the basehash and the
+dependent task hashes can be influenced. Within the BitBake
+configuration file, we can give BitBake some extra information to help
+it construct the basehash. The following statement effectively results
+in a list of global variable dependency excludes - variables never
+included in any checksum. This example uses variables from OpenEmbedded
+to help illustrate the concept: ::
+
+ BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH DL_DIR \
+ SSTATE_DIR THISDIR FILESEXTRAPATHS FILE_DIRNAME HOME LOGNAME SHELL \
+ USER FILESPATH STAGING_DIR_HOST STAGING_DIR_TARGET COREBASE PRSERV_HOST \
+ PRSERV_DUMPDIR PRSERV_DUMPFILE PRSERV_LOCKDOWN PARALLEL_MAKE \
+ CCACHE_DIR EXTERNAL_TOOLCHAIN CCACHE CCACHE_DISABLE LICENSE_PATH SDKPKGSUFFIX"
+
+The previous example excludes the work directory, which is part of
+``TMPDIR``.
+
+The rules for deciding which hashes of dependent tasks to include
+through dependency chains are more complex and are generally
+accomplished with a Python function. The code in
+``meta/lib/oe/sstatesig.py`` shows two examples of this and also
+illustrates how you can insert your own policy into the system if so
+desired. This file defines the two basic signature generators
+OpenEmbedded-Core uses: "OEBasic" and "OEBasicHash". By default, there
+is a dummy "noop" signature handler enabled in BitBake. This means that
+behavior is unchanged from previous versions. ``OE-Core`` uses the
+"OEBasicHash" signature handler by default through this setting in the
+``bitbake.conf`` file: ::
+
+ BB_SIGNATURE_HANDLER ?= "OEBasicHash"
+
+The "OEBasicHash" ``BB_SIGNATURE_HANDLER`` is the same as the "OEBasic"
+version but adds the task hash to the stamp files. This results in any
+metadata change that changes the task hash, automatically causing the
+task to be run again. This removes the need to bump
+:term:`PR` values, and changes to metadata automatically
+ripple across the build.
+
+It is also worth noting that the end result of these signature
+generators is to make some dependency and hash information available to
+the build. This information includes:
+
+- ``BB_BASEHASH_task-``\ *taskname*: The base hashes for each task in the
+ recipe.
+
+- ``BB_BASEHASH_``\ *filename:taskname*: The base hashes for each
+ dependent task.
+
+- ``BBHASHDEPS_``\ *filename:taskname*: The task dependencies for
+ each task.
+
+- ``BB_TASKHASH``: The hash of the currently running task.
+
+It is worth noting that BitBake's "-S" option lets you debug BitBake's
+processing of signatures. The options passed to -S allow different
+debugging modes to be used, either using BitBake's own debug functions
+or possibly those defined in the metadata/signature handler itself. The
+simplest parameter to pass is "none", which causes a set of signature
+information to be written out into ``STAMPS_DIR`` corresponding to the
+targets specified. The other currently available parameter is
+"printdiff", which causes BitBake to try to establish the closest
+signature match it can (e.g. in the sstate cache) and then run
+``bitbake-diffsigs`` over the matches to determine the stamps and delta
+where these two stamp trees diverge.
+
+.. note::
+
+ It is likely that future versions of BitBake will provide other
+ signature handlers triggered through additional "-S" parameters.
+
+You can find more information on checksum metadata in the
+:ref:`bitbake-user-manual/bitbake-user-manual-metadata:task checksums and setscene`
+section.
+
+Setscene
+========
+
+The setscene process enables BitBake to handle "pre-built" artifacts.
+The ability to handle and reuse these artifacts allows BitBake the
+luxury of not having to build something from scratch every time.
+Instead, BitBake can use, when possible, existing build artifacts.
+
+BitBake needs to have reliable data indicating whether or not an
+artifact is compatible. Signatures, described in the previous section,
+provide an ideal way of representing whether an artifact is compatible.
+If a signature is the same, an object can be reused.
+
+If an object can be reused, the problem then becomes how to replace a
+given task or set of tasks with the pre-built artifact. BitBake solves
+the problem with the "setscene" process.
+
+When BitBake is asked to build a given target, before building anything,
+it first asks whether cached information is available for any of the
+targets it's building, or any of the intermediate targets. If cached
+information is available, BitBake uses this information instead of
+running the main tasks.
+
+BitBake first calls the function defined by the
+:term:`BB_HASHCHECK_FUNCTION` variable
+with a list of tasks and corresponding hashes it wants to build. This
+function is designed to be fast and returns a list of the tasks for
+which it believes in can obtain artifacts.
+
+Next, for each of the tasks that were returned as possibilities, BitBake
+executes a setscene version of the task that the possible artifact
+covers. Setscene versions of a task have the string "_setscene" appended
+to the task name. So, for example, the task with the name ``xxx`` has a
+setscene task named ``xxx_setscene``. The setscene version of the task
+executes and provides the necessary artifacts returning either success
+or failure.
+
+As previously mentioned, an artifact can cover more than one task. For
+example, it is pointless to obtain a compiler if you already have the
+compiled binary. To handle this, BitBake calls the
+:term:`BB_SETSCENE_DEPVALID` function for
+each successful setscene task to know whether or not it needs to obtain
+the dependencies of that task.
+
+Finally, after all the setscene tasks have executed, BitBake calls the
+function listed in
+:term:`BB_SETSCENE_VERIFY_FUNCTION2`
+with the list of tasks BitBake thinks has been "covered". The metadata
+can then ensure that this list is correct and can inform BitBake that it
+wants specific tasks to be run regardless of the setscene result.
+
+You can find more information on setscene metadata in the
+:ref:`bitbake-user-manual/bitbake-user-manual-metadata:task checksums and setscene`
+section.
+
+Logging
+=======
+
+In addition to the standard command line option to control how verbose
+builds are when execute, bitbake also supports user defined
+configuration of the `Python
+logging <https://docs.python.org/3/library/logging.html>`__ facilities
+through the :term:`BB_LOGCONFIG` variable. This
+variable defines a json or yaml `logging
+configuration <https://docs.python.org/3/library/logging.config.html>`__
+that will be intelligently merged into the default configuration. The
+logging configuration is merged using the following rules:
+
+- The user defined configuration will completely replace the default
+ configuration if top level key ``bitbake_merge`` is set to the value
+ ``False``. In this case, all other rules are ignored.
+
+- The user configuration must have a top level ``version`` which must
+ match the value of the default configuration.
+
+- Any keys defined in the ``handlers``, ``formatters``, or ``filters``,
+ will be merged into the same section in the default configuration,
+ with the user specified keys taking replacing a default one if there
+ is a conflict. In practice, this means that if both the default
+ configuration and user configuration specify a handler named
+ ``myhandler``, the user defined one will replace the default. To
+ prevent the user from inadvertently replacing a default handler,
+ formatter, or filter, all of the default ones are named with a prefix
+ of "``BitBake.``"
+
+- If a logger is defined by the user with the key ``bitbake_merge`` set
+ to ``False``, that logger will be completely replaced by user
+ configuration. In this case, no other rules will apply to that
+ logger.
+
+- All user defined ``filter`` and ``handlers`` properties for a given
+ logger will be merged with corresponding properties from the default
+ logger. For example, if the user configuration adds a filter called
+ ``myFilter`` to the ``BitBake.SigGen``, and the default configuration
+ adds a filter called ``BitBake.defaultFilter``, both filters will be
+ applied to the logger
+
+As an example, consider the following user logging configuration file
+which logs all Hash Equivalence related messages of VERBOSE or higher to
+a file called ``hashequiv.log`` ::
+
+ {
+ "version": 1,
+ "handlers": {
+ "autobuilderlog": {
+ "class": "logging.FileHandler",
+ "formatter": "logfileFormatter",
+ "level": "DEBUG",
+ "filename": "hashequiv.log",
+ "mode": "w"
+ }
+ },
+ "formatters": {
+ "logfileFormatter": {
+ "format": "%(name)s: %(levelname)s: %(message)s"
+ }
+ },
+ "loggers": {
+ "BitBake.SigGen.HashEquiv": {
+ "level": "VERBOSE",
+ "handlers": ["autobuilderlog"]
+ },
+ "BitBake.RunQueue.HashEquiv": {
+ "level": "VERBOSE",
+ "handlers": ["autobuilderlog"]
+ }
+ }
+ }