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Andrew Geisslerc9f78652020-09-18 14:11:35 -05002
3************************************************
4Board Support Packages (BSP) - Developer's Guide
5************************************************
6
7A Board Support Package (BSP) is a collection of information that
8defines how to support a particular hardware device, set of devices, or
9hardware platform. The BSP includes information about the hardware
10features present on the device and kernel configuration information
11along with any additional hardware drivers required. The BSP also lists
12any additional software components required in addition to a generic
13Linux software stack for both essential and optional platform features.
14
15This guide presents information about BSP layers, defines a structure
16for components so that BSPs follow a commonly understood layout,
17discusses how to customize a recipe for a BSP, addresses BSP licensing,
18and provides information that shows you how to create a BSP
19Layer using the :ref:`bitbake-layers <bsp-guide/bsp:Creating a new BSP Layer Using the \`\`bitbake-layers\`\` Script>`
20tool.
21
22BSP Layers
23==========
24
25A BSP consists of a file structure inside a base directory.
26Collectively, you can think of the base directory, its file structure,
27and the contents as a BSP layer. Although not a strict requirement, BSP
28layers in the Yocto Project use the following well-established naming
29convention: ::
30
31 meta-bsp_root_name
32
33The string "meta-" is prepended to the
Andrew Geissler4c19ea12020-10-27 13:52:24 -050034machine or platform name, which is "bsp_root_name" in the above form.
Andrew Geisslerc9f78652020-09-18 14:11:35 -050035
36.. note::
37
38 Because the BSP layer naming convention is well-established, it is
39 advisable to follow it when creating layers. Technically speaking, a
Andrew Geissler4c19ea12020-10-27 13:52:24 -050040 BSP layer name does not need to start with ``meta-``.
41 However, various scripts and tools in the Yocto Project development
Andrew Geisslerc9f78652020-09-18 14:11:35 -050042 environment assume this convention.
43
44To help understand the BSP layer concept, consider the BSPs that the
45Yocto Project supports and provides with each release. You can see the
46layers in the
Andrew Geissler09209ee2020-12-13 08:44:15 -060047:ref:`overview-manual/development-environment:yocto project source repositories`
Andrew Geisslerc9f78652020-09-18 14:11:35 -050048through
49a web interface at :yocto_git:`/`. If you go to that interface,
50you will find a list of repositories under "Yocto Metadata Layers".
51
52.. note::
53
54 Layers that are no longer actively supported as part of the Yocto
55 Project appear under the heading "Yocto Metadata Layer Archive."
56
57Each repository is a BSP layer supported by the Yocto Project (e.g.
58``meta-raspberrypi`` and ``meta-intel``). Each of these layers is a
59repository unto itself and clicking on the layer name displays two URLs
60from which you can clone the layer's repository to your local system.
61Here is an example that clones the Raspberry Pi BSP layer: ::
62
63 $ git clone git://git.yoctoproject.org/meta-raspberrypi
64
65In addition to BSP layers, the ``meta-yocto-bsp`` layer is part of the
66shipped ``poky`` repository. The ``meta-yocto-bsp`` layer maintains
67several "reference" BSPs including the ARM-based Beaglebone, MIPS-based
68EdgeRouter, and generic versions of both 32-bit and 64-bit IA machines.
69
70For information on typical BSP development workflow, see the
71:ref:`bsp-guide/bsp:developing a board support package (bsp)`
72section. For more
73information on how to set up a local copy of source files from a Git
74repository, see the
Andrew Geissler09209ee2020-12-13 08:44:15 -060075:ref:`dev-manual/start:locating yocto project source files`
Andrew Geisslerc9f78652020-09-18 14:11:35 -050076section in the Yocto Project Development Tasks Manual.
77
78The BSP layer's base directory (``meta-bsp_root_name``) is the root
79directory of that Layer. This directory is what you add to the
80:term:`BBLAYERS` variable in the
81``conf/bblayers.conf`` file found in your
82:term:`Build Directory`, which is
83established after you run the OpenEmbedded build environment setup
Andrew Geissler09209ee2020-12-13 08:44:15 -060084script (i.e. :ref:`ref-manual/structure:\`\`oe-init-build-env\`\``).
Andrew Geisslerc9f78652020-09-18 14:11:35 -050085Adding the root directory allows the :term:`OpenEmbedded Build System`
86to recognize the BSP
87layer and from it build an image. Here is an example: ::
88
89 BBLAYERS ?= " \
90 /usr/local/src/yocto/meta \
91 /usr/local/src/yocto/meta-poky \
92 /usr/local/src/yocto/meta-yocto-bsp \
93 /usr/local/src/yocto/meta-mylayer \
94 "
95
96.. note::
97
Andrew Geissler4c19ea12020-10-27 13:52:24 -050098 Ordering and :term:`BBFILE_PRIORITY` for the layers listed in ``BBLAYERS``
99 matter. For example, if multiple layers define a machine configuration, the
100 OpenEmbedded build system uses the last layer searched given similar layer
101 priorities. The build system works from the top-down through the layers
102 listed in ``BBLAYERS``.
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500103
104Some BSPs require or depend on additional layers beyond the BSP's root
105layer in order to be functional. In this case, you need to specify these
106layers in the ``README`` "Dependencies" section of the BSP's root layer.
107Additionally, if any build instructions exist for the BSP, you must add
108them to the "Dependencies" section.
109
110Some layers function as a layer to hold other BSP layers. These layers
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500111are known as ":term:`container layers <Container Layer>`". An example of
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500112this type of layer is OpenEmbedded's
113`meta-openembedded <https://github.com/openembedded/meta-openembedded>`__
114layer. The ``meta-openembedded`` layer contains many ``meta-*`` layers.
115In cases like this, you need to include the names of the actual layers
116you want to work with, such as: ::
117
118 BBLAYERS ?= " \
119 /usr/local/src/yocto/meta \
120 /usr/local/src/yocto/meta-poky \
121 /usr/local/src/yocto/meta-yocto-bsp \
122 /usr/local/src/yocto/meta-mylayer \
123 .../meta-openembedded/meta-oe \
124 .../meta-openembedded/meta-perl \
125 .../meta-openembedded/meta-networking \
126 "
127
128and so on.
129
130For more information on layers, see the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600131":ref:`dev-manual/common-tasks:understanding and creating layers`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500132section of the Yocto Project Development Tasks Manual.
133
134Preparing Your Build Host to Work With BSP Layers
135=================================================
136
137This section describes how to get your build host ready to work with BSP
138layers. Once you have the host set up, you can create the layer as
139described in the
140":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
141section.
142
143.. note::
144
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500145 For structural information on BSPs, see the
146 :ref:`bsp-guide/bsp:example filesystem layout` section.
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500147
148#. *Set Up the Build Environment:* Be sure you are set up to use BitBake
Andrew Geissler09209ee2020-12-13 08:44:15 -0600149 in a shell. See the ":ref:`dev-manual/start:preparing the build host`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500150 section in the Yocto Project Development Tasks Manual for information on how
151 to get a build host ready that is either a native Linux machine or a machine
152 that uses CROPS.
153
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500154#. *Clone the poky Repository:* You need to have a local copy of the
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500155 Yocto Project :term:`Source Directory` (i.e. a local
156 ``poky`` repository). See the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600157 ":ref:`dev-manual/start:cloning the \`\`poky\`\` repository`" and
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500158 possibly the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600159 ":ref:`dev-manual/start:checking out by branch in poky`" or
160 ":ref:`dev-manual/start:checking out by tag in poky`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500161 sections
162 all in the Yocto Project Development Tasks Manual for information on
163 how to clone the ``poky`` repository and check out the appropriate
164 branch for your work.
165
166#. *Determine the BSP Layer You Want:* The Yocto Project supports many
167 BSPs, which are maintained in their own layers or in layers designed
168 to contain several BSPs. To get an idea of machine support through
169 BSP layers, you can look at the `index of
170 machines <&YOCTO_RELEASE_DL_URL;/machines>`__ for the release.
171
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500172#. *Optionally Clone the meta-intel BSP Layer:* If your hardware is
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500173 based on current Intel CPUs and devices, you can leverage this BSP
174 layer. For details on the ``meta-intel`` BSP layer, see the layer's
Andrew Geissler09209ee2020-12-13 08:44:15 -0600175 :yocto_git:`README </meta-intel/tree/README>` file.
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500176
177 #. *Navigate to Your Source Directory:* Typically, you set up the
178 ``meta-intel`` Git repository inside the :term:`Source Directory` (e.g.
179 ``poky``). ::
180
181 $ cd /home/you/poky
182
183 #. *Clone the Layer:* ::
184
185 $ git clone git://git.yoctoproject.org/meta-intel.git
186 Cloning into 'meta-intel'...
187 remote: Counting objects: 15585, done.
188 remote: Compressing objects: 100% (5056/5056), done.
189 remote: Total 15585 (delta 9123), reused 15329 (delta 8867)
190 Receiving objects: 100% (15585/15585), 4.51 MiB | 3.19 MiB/s, done.
191 Resolving deltas: 100% (9123/9123), done.
192 Checking connectivity... done.
193
194 #. *Check Out the Proper Branch:* The branch you check out for
195 ``meta-intel`` must match the same branch you are using for the
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500196 Yocto Project release (e.g. ``&DISTRO_NAME_NO_CAP;``): ::
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500197
198 $ cd meta-intel
199 $ git checkout -b &DISTRO_NAME_NO_CAP; remotes/origin/&DISTRO_NAME_NO_CAP;
200 Branch &DISTRO_NAME_NO_CAP; set up to track remote branch
201 &DISTRO_NAME_NO_CAP; from origin.
202 Switched to a new branch '&DISTRO_NAME_NO_CAP;'
203
204 .. note::
205
206 To see the available branch names in a cloned repository, use the ``git
207 branch -al`` command. See the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600208 ":ref:`dev-manual/start:checking out by branch in poky`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500209 section in the Yocto Project Development Tasks Manual for more
210 information.
211
212#. *Optionally Set Up an Alternative BSP Layer:* If your hardware can be
213 more closely leveraged to an existing BSP not within the
214 ``meta-intel`` BSP layer, you can clone that BSP layer.
215
216 The process is identical to the process used for the ``meta-intel``
217 layer except for the layer's name. For example, if you determine that
218 your hardware most closely matches the ``meta-raspberrypi``, clone
219 that layer: ::
220
221 $ git clone git://git.yoctoproject.org/meta-raspberrypi
222 Cloning into 'meta-raspberrypi'...
223 remote: Counting objects: 4743, done.
224 remote: Compressing objects: 100% (2185/2185), done.
225 remote: Total 4743 (delta 2447), reused 4496 (delta 2258)
226 Receiving objects: 100% (4743/4743), 1.18 MiB | 0 bytes/s, done.
227 Resolving deltas: 100% (2447/2447), done.
228 Checking connectivity... done.
229
230#. *Initialize the Build Environment:* While in the root directory of
231 the Source Directory (i.e. ``poky``), run the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600232 :ref:`ref-manual/structure:\`\`oe-init-build-env\`\`` environment
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500233 setup script to define the OpenEmbedded build environment on your
234 build host. ::
235
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500236 $ source oe-init-build-env
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500237
238 Among other things, the script creates the :term:`Build Directory`, which is
239 ``build`` in this case and is located in the :term:`Source Directory`. After
240 the script runs, your current working directory is set to the ``build``
241 directory.
242
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500243Example Filesystem Layout
244=========================
245
246Defining a common BSP directory structure allows end-users to understand
247and become familiar with that standard. A common format also encourages
248standardization of software support for hardware.
249
250The proposed form described in this section does have elements that are
251specific to the OpenEmbedded build system. It is intended that
252developers can use this structure with other build systems besides the
253OpenEmbedded build system. It is also intended that it will be be simple
254to extract information and convert it to other formats if required. The
255OpenEmbedded build system, through its standard :ref:`layers mechanism
Andrew Geissler09209ee2020-12-13 08:44:15 -0600256<overview-manual/yp-intro:the yocto project layer model>`, can
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500257directly accept the format described as a layer. The BSP layer captures
258all the hardware-specific details in one place using a standard format,
259which is useful for any person wishing to use the hardware platform
260regardless of the build system they are using.
261
262The BSP specification does not include a build system or other tools -
263the specification is concerned with the hardware-specific components
264only. At the end-distribution point, you can ship the BSP layer combined
265with a build system and other tools. Realize that it is important to
266maintain the distinction that the BSP layer, a build system, and tools
267are separate components that could be combined in certain end products.
268
269Before looking at the recommended form for the directory structure
270inside a BSP layer, you should be aware that some requirements do exist
271in order for a BSP layer to be considered compliant with the Yocto
272Project. For that list of requirements, see the
273":ref:`bsp-guide/bsp:released bsp requirements`" section.
274
275Below is the typical directory structure for a BSP layer. While this
276basic form represents the standard, realize that the actual layout for
277individual BSPs could differ. ::
278
279 meta-bsp_root_name/
280 meta-bsp_root_name/bsp_license_file
281 meta-bsp_root_name/README
282 meta-bsp_root_name/README.sources
283 meta-bsp_root_name/binary/bootable_images
284 meta-bsp_root_name/conf/layer.conf
285 meta-bsp_root_name/conf/machine/*.conf
286 meta-bsp_root_name/recipes-bsp/*
287 meta-bsp_root_name/recipes-core/*
288 meta-bsp_root_name/recipes-graphics/*
289 meta-bsp_root_name/recipes-kernel/linux/linux-yocto_kernel_rev.bbappend
290
291Below is an example of the Raspberry Pi BSP layer that is available from
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500292the :yocto_git:`Source Respositories <>`:
293
294.. code-block:: none
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500295
296 meta-raspberrypi/COPYING.MIT
297 meta-raspberrypi/README.md
298 meta-raspberrypi/classes
299 meta-raspberrypi/classes/sdcard_image-rpi.bbclass
300 meta-raspberrypi/conf/
301 meta-raspberrypi/conf/layer.conf
302 meta-raspberrypi/conf/machine/
303 meta-raspberrypi/conf/machine/raspberrypi-cm.conf
304 meta-raspberrypi/conf/machine/raspberrypi-cm3.conf
305 meta-raspberrypi/conf/machine/raspberrypi.conf
306 meta-raspberrypi/conf/machine/raspberrypi0-wifi.conf
307 meta-raspberrypi/conf/machine/raspberrypi0.conf
308 meta-raspberrypi/conf/machine/raspberrypi2.conf
309 meta-raspberrypi/conf/machine/raspberrypi3-64.conf
310 meta-raspberrypi/conf/machine/raspberrypi3.conf
311 meta-raspberrypi/conf/machine/include
312 meta-raspberrypi/conf/machine/include/rpi-base.inc
313 meta-raspberrypi/conf/machine/include/rpi-default-providers.inc
314 meta-raspberrypi/conf/machine/include/rpi-default-settings.inc
315 meta-raspberrypi/conf/machine/include/rpi-default-versions.inc
316 meta-raspberrypi/conf/machine/include/tune-arm1176jzf-s.inc
317 meta-raspberrypi/docs
318 meta-raspberrypi/docs/Makefile
319 meta-raspberrypi/docs/conf.py
320 meta-raspberrypi/docs/contributing.md
321 meta-raspberrypi/docs/extra-apps.md
322 meta-raspberrypi/docs/extra-build-config.md
323 meta-raspberrypi/docs/index.rst
324 meta-raspberrypi/docs/layer-contents.md
325 meta-raspberrypi/docs/readme.md
326 meta-raspberrypi/files
327 meta-raspberrypi/files/custom-licenses
328 meta-raspberrypi/files/custom-licenses/Broadcom
329 meta-raspberrypi/recipes-bsp
330 meta-raspberrypi/recipes-bsp/bootfiles
331 meta-raspberrypi/recipes-bsp/bootfiles/bcm2835-bootfiles.bb
332 meta-raspberrypi/recipes-bsp/bootfiles/rpi-config_git.bb
333 meta-raspberrypi/recipes-bsp/common
334 meta-raspberrypi/recipes-bsp/common/firmware.inc
335 meta-raspberrypi/recipes-bsp/formfactor
336 meta-raspberrypi/recipes-bsp/formfactor/formfactor
337 meta-raspberrypi/recipes-bsp/formfactor/formfactor/raspberrypi
338 meta-raspberrypi/recipes-bsp/formfactor/formfactor/raspberrypi/machconfig
339 meta-raspberrypi/recipes-bsp/formfactor/formfactor_0.0.bbappend
340 meta-raspberrypi/recipes-bsp/rpi-u-boot-src
341 meta-raspberrypi/recipes-bsp/rpi-u-boot-src/files
342 meta-raspberrypi/recipes-bsp/rpi-u-boot-src/files/boot.cmd.in
343 meta-raspberrypi/recipes-bsp/rpi-u-boot-src/rpi-u-boot-scr.bb
344 meta-raspberrypi/recipes-bsp/u-boot
345 meta-raspberrypi/recipes-bsp/u-boot/u-boot
346 meta-raspberrypi/recipes-bsp/u-boot/u-boot/*.patch
347 meta-raspberrypi/recipes-bsp/u-boot/u-boot_%.bbappend
348 meta-raspberrypi/recipes-connectivity
349 meta-raspberrypi/recipes-connectivity/bluez5
350 meta-raspberrypi/recipes-connectivity/bluez5/bluez5
351 meta-raspberrypi/recipes-connectivity/bluez5/bluez5/*.patch
352 meta-raspberrypi/recipes-connectivity/bluez5/bluez5/BCM43430A1.hcd
353 meta-raspberrypi/recipes-connectivity/bluez5/bluez5brcm43438.service
354 meta-raspberrypi/recipes-connectivity/bluez5/bluez5_%.bbappend
355 meta-raspberrypi/recipes-core
356 meta-raspberrypi/recipes-core/images
357 meta-raspberrypi/recipes-core/images/rpi-basic-image.bb
358 meta-raspberrypi/recipes-core/images/rpi-hwup-image.bb
359 meta-raspberrypi/recipes-core/images/rpi-test-image.bb
360 meta-raspberrypi/recipes-core/packagegroups
361 meta-raspberrypi/recipes-core/packagegroups/packagegroup-rpi-test.bb
362 meta-raspberrypi/recipes-core/psplash
363 meta-raspberrypi/recipes-core/psplash/files
364 meta-raspberrypi/recipes-core/psplash/files/psplash-raspberrypi-img.h
365 meta-raspberrypi/recipes-core/psplash/psplash_git.bbappend
366 meta-raspberrypi/recipes-core/udev
367 meta-raspberrypi/recipes-core/udev/udev-rules-rpi
368 meta-raspberrypi/recipes-core/udev/udev-rules-rpi/99-com.rules
369 meta-raspberrypi/recipes-core/udev/udev-rules-rpi.bb
370 meta-raspberrypi/recipes-devtools
371 meta-raspberrypi/recipes-devtools/bcm2835
372 meta-raspberrypi/recipes-devtools/bcm2835/bcm2835_1.52.bb
373 meta-raspberrypi/recipes-devtools/pi-blaster
374 meta-raspberrypi/recipes-devtools/pi-blaster/files
375 meta-raspberrypi/recipes-devtools/pi-blaster/files/*.patch
376 meta-raspberrypi/recipes-devtools/pi-blaster/pi-blaster_git.bb
377 meta-raspberrypi/recipes-devtools/python
378 meta-raspberrypi/recipes-devtools/python/python-rtimu
379 meta-raspberrypi/recipes-devtools/python/python-rtimu/*.patch
380 meta-raspberrypi/recipes-devtools/python/python-rtimu_git.bb
381 meta-raspberrypi/recipes-devtools/python/python-sense-hat_2.2.0.bb
382 meta-raspberrypi/recipes-devtools/python/rpi-gpio
383 meta-raspberrypi/recipes-devtools/python/rpi-gpio/*.patch
384 meta-raspberrypi/recipes-devtools/python/rpi-gpio_0.6.3.bb
385 meta-raspberrypi/recipes-devtools/python/rpio
386 meta-raspberrypi/recipes-devtools/python/rpio/*.patch
387 meta-raspberrypi/recipes-devtools/python/rpio_0.10.0.bb
388 meta-raspberrypi/recipes-devtools/wiringPi
389 meta-raspberrypi/recipes-devtools/wiringPi/files
390 meta-raspberrypi/recipes-devtools/wiringPi/files/*.patch
391 meta-raspberrypi/recipes-devtools/wiringPi/wiringpi_git.bb
392 meta-raspberrypi/recipes-graphics
393 meta-raspberrypi/recipes-graphics/eglinfo
394 meta-raspberrypi/recipes-graphics/eglinfo/eglinfo-fb_%.bbappend
395 meta-raspberrypi/recipes-graphics/eglinfo/eglinfo-x11_%.bbappend
396 meta-raspberrypi/recipes-graphics/mesa
397 meta-raspberrypi/recipes-graphics/mesa/mesa-gl_%.bbappend
398 meta-raspberrypi/recipes-graphics/mesa/mesa_%.bbappend
399 meta-raspberrypi/recipes-graphics/userland
400 meta-raspberrypi/recipes-graphics/userland/userland
401 meta-raspberrypi/recipes-graphics/userland/userland/*.patch
402 meta-raspberrypi/recipes-graphics/userland/userland_git.bb
403 meta-raspberrypi/recipes-graphics/vc-graphics
404 meta-raspberrypi/recipes-graphics/vc-graphics/files
405 meta-raspberrypi/recipes-graphics/vc-graphics/files/egl.pc
406 meta-raspberrypi/recipes-graphics/vc-graphics/files/vchiq.sh
407 meta-raspberrypi/recipes-graphics/vc-graphics/vc-graphics-hardfp.bb
408 meta-raspberrypi/recipes-graphics/vc-graphics/vc-graphics.bb
409 meta-raspberrypi/recipes-graphics/vc-graphics/vc-graphics.inc
410 meta-raspberrypi/recipes-graphics/wayland
411 meta-raspberrypi/recipes-graphics/wayland/weston_%.bbappend
412 meta-raspberrypi/recipes-graphics/xorg-xserver
413 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config
414 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi
415 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf
416 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d
417 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d/10-evdev.conf
418 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d/98-pitft.conf
419 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d/99-calibration.conf
420 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config_0.1.bbappend
421 meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xorg_%.bbappend
422 meta-raspberrypi/recipes-kernel
423 meta-raspberrypi/recipes-kernel/linux-firmware
424 meta-raspberrypi/recipes-kernel/linux-firmware/files
425 meta-raspberrypi/recipes-kernel/linux-firmware/files/brcmfmac43430-sdio.bin
426 meta-raspberrypi/recipes-kernel/linux-firmware/files/brcfmac43430-sdio.txt
427 meta-raspberrypi/recipes-kernel/linux-firmware/linux-firmware_%.bbappend
428 meta-raspberrypi/recipes-kernel/linux
429 meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-dev.bb
430 meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi.inc
431 meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi_4.14.bb
432 meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi_4.9.bb
433 meta-raspberrypi/recipes-multimedia
434 meta-raspberrypi/recipes-multimedia/gstreamer
435 meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx
436 meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx/*.patch
437 meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx_%.bbappend
438 meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-plugins-bad_%.bbappend
439 meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx-1.12
440 meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx-1.12/*.patch
441 meta-raspberrypi/recipes-multimedia/omxplayer
442 meta-raspberrypi/recipes-multimedia/omxplayer/omxplayer
443 meta-raspberrypi/recipes-multimedia/omxplayer/omxplayer/*.patch
444 meta-raspberrypi/recipes-multimedia/omxplayer/omxplayer_git.bb
445 meta-raspberrypi/recipes-multimedia/x264
446 meta-raspberrypi/recipes-multimedia/x264/x264_git.bbappend
447 meta-raspberrypi/wic meta-raspberrypi/wic/sdimage-raspberrypi.wks
448
449The following sections describe each part of the proposed BSP format.
450
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500451License Files
452-------------
453
454You can find these files in the BSP Layer at: ::
455
456 meta-bsp_root_name/bsp_license_file
457
458These optional files satisfy licensing requirements for the BSP. The
459type or types of files here can vary depending on the licensing
460requirements. For example, in the Raspberry Pi BSP, all licensing
461requirements are handled with the ``COPYING.MIT`` file.
462
463Licensing files can be MIT, BSD, GPLv*, and so forth. These files are
464recommended for the BSP but are optional and totally up to the BSP
465developer. For information on how to maintain license compliance, see
Andrew Geissler09209ee2020-12-13 08:44:15 -0600466the ":ref:`dev-manual/common-tasks:maintaining open source license compliance during your product's lifecycle`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500467section in the Yocto Project Development Tasks Manual.
468
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500469README File
470-----------
471
472You can find this file in the BSP Layer at: ::
473
474 meta-bsp_root_name/README
475
476This file provides information on how to boot the live images that are
477optionally included in the ``binary/`` directory. The ``README`` file
478also provides information needed for building the image.
479
480At a minimum, the ``README`` file must contain a list of dependencies,
481such as the names of any other layers on which the BSP depends and the
482name of the BSP maintainer with his or her contact information.
483
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500484README.sources File
485-------------------
486
487You can find this file in the BSP Layer at: ::
488
489 meta-bsp_root_name/README.sources
490
491This file provides information on where to locate the BSP source files
492used to build the images (if any) that reside in
493``meta-bsp_root_name/binary``. Images in the ``binary`` would be images
494released with the BSP. The information in the ``README.sources`` file
495also helps you find the :term:`Metadata`
496used to generate the images that ship with the BSP.
497
498.. note::
499
500 If the BSP's ``binary`` directory is missing or the directory has no images, an
501 existing ``README.sources`` file is meaningless and usually does not exist.
502
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500503Pre-built User Binaries
504-----------------------
505
506You can find these files in the BSP Layer at: ::
507
508 meta-bsp_root_name/binary/bootable_images
509
510This optional area contains useful pre-built kernels and user-space
511filesystem images released with the BSP that are appropriate to the
512target system. This directory typically contains graphical (e.g. Sato)
513and minimal live images when the BSP tarball has been created and made
514available in the :yocto_home:`Yocto Project <>` website. You can
515use these kernels and images to get a system running and quickly get
516started on development tasks.
517
518The exact types of binaries present are highly hardware-dependent. The
519:ref:`README <bsp-guide/bsp:readme file>` file should be present in the
520BSP Layer and it explains how to use the images with the target
521hardware. Additionally, the
522:ref:`README.sources <bsp-guide/bsp:readme.sources file>` file should be
523present to locate the sources used to build the images and provide
524information on the Metadata.
525
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500526Layer Configuration File
527------------------------
528
529You can find this file in the BSP Layer at: ::
530
531 meta-bsp_root_name/conf/layer.conf
532
533The ``conf/layer.conf`` file identifies the file structure as a layer,
534identifies the contents of the layer, and contains information about how
535the build system should use it. Generally, a standard boilerplate file
536such as the following works. In the following example, you would replace
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500537"bsp" with the actual name of the BSP (i.e. "bsp_root_name" from the example
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500538template). ::
539
540 # We have a conf and classes directory, add to BBPATH
541 BBPATH .= ":${LAYERDIR}"
542
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500543 # We have a recipes directory containing .bb and .bbappend files, add to BBFILES
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500544 BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
545 ${LAYERDIR}/recipes-*/*/*.bbappend"
546
547 BBFILE_COLLECTIONS += "bsp"
548 BBFILE_PATTERN_bsp = "^${LAYERDIR}/"
549 BBFILE_PRIORITY_bsp = "6"
550 LAYERDEPENDS_bsp = "intel"
551
552To illustrate the string substitutions, here are the corresponding
553statements from the Raspberry Pi ``conf/layer.conf`` file: ::
554
555 # We have a conf and classes directory, append to BBPATH
556 BBPATH .= ":${LAYERDIR}"
557
558 # We have a recipes directory containing .bb and .bbappend files, add to BBFILES
559 BBFILES += "${LAYERDIR}/recipes*/*/*.bb \
560 ${LAYERDIR}/recipes*/*/*.bbappend"
561
562 BBFILE_COLLECTIONS += "raspberrypi"
563 BBFILE_PATTERN_raspberrypi := "^${LAYERDIR}/"
564 BBFILE_PRIORITY_raspberrypi = "9"
565
566 # Additional license directories.
567 LICENSE_PATH += "${LAYERDIR}/files/custom-licenses"
568 .
569 .
570 .
571
572This file simply makes :term:`BitBake` aware of the recipes and configuration
573directories. The file must exist so that the OpenEmbedded build system can
574recognize the BSP.
575
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500576Hardware Configuration Options
577------------------------------
578
579You can find these files in the BSP Layer at: ::
580
581 meta-bsp_root_name/conf/machine/*.conf
582
583The machine files bind together all the information contained elsewhere
584in the BSP into a format that the build system can understand. Each BSP
585Layer requires at least one machine file. If the BSP supports multiple
586machines, multiple machine configuration files can exist. These
587filenames correspond to the values to which users have set the
588:term:`MACHINE` variable.
589
590These files define things such as the kernel package to use
591(:term:`PREFERRED_PROVIDER` of
Andrew Geissler09209ee2020-12-13 08:44:15 -0600592:ref:`virtual/kernel <dev-manual/common-tasks:using virtual providers>`),
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500593the hardware drivers to include in different types of images, any
594special software components that are needed, any bootloader information,
595and also any special image format requirements.
596
597This configuration file could also include a hardware "tuning" file that
598is commonly used to define the package architecture and specify
599optimization flags, which are carefully chosen to give best performance
600on a given processor.
601
602Tuning files are found in the ``meta/conf/machine/include`` directory
603within the :term:`Source Directory`.
604For example, many ``tune-*`` files (e.g. ``tune-arm1136jf-s.inc``,
605``tune-1586-nlp.inc``, and so forth) reside in the
606``poky/meta/conf/machine/include`` directory.
607
608To use an include file, you simply include them in the machine
609configuration file. For example, the Raspberry Pi BSP
610``raspberrypi3.conf`` contains the following statement: ::
611
612 include conf/machine/include/rpi-base.inc
613
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500614Miscellaneous BSP-Specific Recipe Files
615---------------------------------------
616
617You can find these files in the BSP Layer at: ::
618
619 meta-bsp_root_name/recipes-bsp/*
620
621This optional directory contains miscellaneous recipe files for the BSP.
622Most notably would be the formfactor files. For example, in the
623Raspberry Pi BSP, there is the ``formfactor_0.0.bbappend`` file, which
624is an append file used to augment the recipe that starts the build.
625Furthermore, there are machine-specific settings used during the build
626that are defined by the ``machconfig`` file further down in the
627directory. Here is the ``machconfig`` file for the Raspberry Pi BSP: ::
628
629 HAVE_TOUCHSCREEN=0
630 HAVE_KEYBOARD=1
631
632 DISPLAY_CAN_ROTATE=0
633 DISPLAY_ORIENTATION=0
634 DISPLAY_DPI=133
635
636.. note::
637
638 If a BSP does not have a formfactor entry, defaults are established
639 according to the formfactor configuration file that is installed by
640 the main formfactor recipe
641 ``meta/recipes-bsp/formfactor/formfactor_0.0.bb``, which is found in
642 the :term:`Source Directory`.
643
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500644Display Support Files
645---------------------
646
647You can find these files in the BSP Layer at: ::
648
649 meta-bsp_root_name/recipes-graphics/*
650
651This optional directory contains recipes for the BSP if it has special
652requirements for graphics support. All files that are needed for the BSP
653to support a display are kept here.
654
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500655Linux Kernel Configuration
656--------------------------
657
658You can find these files in the BSP Layer at: ::
659
660 meta-bsp_root_name/recipes-kernel/linux/linux*.bbappend
661 meta-bsp_root_name/recipes-kernel/linux/*.bb
662
663Append files (``*.bbappend``) modify the main kernel recipe being used
664to build the image. The ``*.bb`` files would be a developer-supplied
665kernel recipe. This area of the BSP hierarchy can contain both these
666types of files although, in practice, it is likely that you would have
667one or the other.
668
669For your BSP, you typically want to use an existing Yocto Project kernel
670recipe found in the :term:`Source Directory`
671at
672``meta/recipes-kernel/linux``. You can append machine-specific changes
673to the kernel recipe by using a similarly named append file, which is
674located in the BSP Layer for your target device (e.g. the
675``meta-bsp_root_name/recipes-kernel/linux`` directory).
676
677Suppose you are using the ``linux-yocto_4.4.bb`` recipe to build the
678kernel. In other words, you have selected the kernel in your
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500679``"bsp_root_name".conf`` file by adding
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500680:term:`PREFERRED_PROVIDER` and :term:`PREFERRED_VERSION`
681statements as follows: ::
682
683 PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
684 PREFERRED_VERSION_linux-yocto ?= "4.4%"
685
686.. note::
687
688 When the preferred provider is assumed by default, the ``PREFERRED_PROVIDER``
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500689 statement does not appear in the ``"bsp_root_name".conf`` file.
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500690
691You would use the ``linux-yocto_4.4.bbappend`` file to append specific
692BSP settings to the kernel, thus configuring the kernel for your
693particular BSP.
694
695You can find more information on what your append file should contain in
Andrew Geissler09209ee2020-12-13 08:44:15 -0600696the ":ref:`kernel-dev/common:creating the append file`" section
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500697in the Yocto Project Linux Kernel Development Manual.
698
699An alternate scenario is when you create your own kernel recipe for the
700BSP. A good example of this is the Raspberry Pi BSP. If you examine the
701``recipes-kernel/linux`` directory you see the following: ::
702
703 linux-raspberrypi-dev.bb
704 linux-raspberrypi.inc
705 linux-raspberrypi_4.14.bb
706 linux-raspberrypi_4.9.bb
707
708The directory contains three kernel recipes and a common include file.
709
710Developing a Board Support Package (BSP)
711========================================
712
713This section describes the high-level procedure you can follow to create
714a BSP. Although not required for BSP creation, the ``meta-intel``
715repository, which contains many BSPs supported by the Yocto Project, is
716part of the example.
717
718For an example that shows how to create a new layer using the tools, see
719the ":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
720section.
721
722The following illustration and list summarize the BSP creation general
723workflow.
724
725.. image:: figures/bsp-dev-flow.png
726 :align: center
727
728#. *Set up Your Host Development System to Support Development Using the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600729 Yocto Project*: See the ":ref:`dev-manual/start:preparing the build host`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500730 section in the Yocto Project Development Tasks Manual for options on how to
731 get a system ready to use the Yocto Project.
732
733#. *Establish the meta-intel Repository on Your System:* Having
734 local copies of these supported BSP layers on your system gives you
735 access to layers you might be able to leverage when creating your
736 BSP. For information on how to get these files, see the
737 ":ref:`bsp-guide/bsp:preparing your build host to work with bsp layers`"
738 section.
739
740#. *Create Your Own BSP Layer Using the bitbake-layers Script:*
741 Layers are ideal for isolating and storing work for a given piece of
742 hardware. A layer is really just a location or area in which you
743 place the recipes and configurations for your BSP. In fact, a BSP is,
744 in itself, a special type of layer. The simplest way to create a new
745 BSP layer that is compliant with the Yocto Project is to use the
746 ``bitbake-layers`` script. For information about that script, see the
747 ":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
748 section.
749
750 Another example that illustrates a layer is an application. Suppose
751 you are creating an application that has library or other
752 dependencies in order for it to compile and run. The layer, in this
753 case, would be where all the recipes that define those dependencies
754 are kept. The key point for a layer is that it is an isolated area
755 that contains all the relevant information for the project that the
756 OpenEmbedded build system knows about. For more information on
Andrew Geissler09209ee2020-12-13 08:44:15 -0600757 layers, see the ":ref:`overview-manual/yp-intro:the yocto project layer model`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500758 section in the Yocto Project Overview and Concepts Manual. You can also
Andrew Geissler09209ee2020-12-13 08:44:15 -0600759 reference the ":ref:`dev-manual/common-tasks:understanding and creating layers`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500760 section in the Yocto Project Development Tasks Manual. For more
761 information on BSP layers, see the ":ref:`bsp-guide/bsp:bsp layers`"
762 section.
763
764 .. note::
765
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500766 - Four hardware reference BSPs exist that are part of the Yocto
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500767 Project release and are located in the ``poky/meta-yocto-bsp``
768 BSP layer:
769
770 - Texas Instruments Beaglebone (``beaglebone-yocto``)
771
772 - Ubiquiti Networks EdgeRouter Lite (``edgerouter``)
773
774 - Two general IA platforms (``genericx86`` and ``genericx86-64``)
775
776 - Three core Intel BSPs exist as part of the Yocto Project
777 release in the ``meta-intel`` layer:
778
779 - ``intel-core2-32``, which is a BSP optimized for the Core2
780 family of CPUs as well as all CPUs prior to the Silvermont
781 core.
782
783 - ``intel-corei7-64``, which is a BSP optimized for Nehalem
784 and later Core and Xeon CPUs as well as Silvermont and later
785 Atom CPUs, such as the Baytrail SoCs.
786
787 - ``intel-quark``, which is a BSP optimized for the Intel
788 Galileo gen1 & gen2 development boards.
789
790 When you set up a layer for a new BSP, you should follow a standard
791 layout. This layout is described in the ":ref:`bsp-guide/bsp:example filesystem layout`"
792 section. In the standard layout, notice
793 the suggested structure for recipes and configuration information.
794 You can see the standard layout for a BSP by examining any supported
795 BSP found in the ``meta-intel`` layer inside the Source Directory.
796
797#. *Make Configuration Changes to Your New BSP Layer:* The standard BSP
798 layer structure organizes the files you need to edit in ``conf`` and
799 several ``recipes-*`` directories within the BSP layer. Configuration
800 changes identify where your new layer is on the local system and
801 identifies the kernel you are going to use. When you run the
802 ``bitbake-layers`` script, you are able to interactively configure
803 many things for the BSP (e.g. keyboard, touchscreen, and so forth).
804
805#. *Make Recipe Changes to Your New BSP Layer:* Recipe changes include
806 altering recipes (``*.bb`` files), removing recipes you do not use,
807 and adding new recipes or append files (``.bbappend``) that support
808 your hardware.
809
810#. *Prepare for the Build:* Once you have made all the changes to your
811 BSP layer, there remains a few things you need to do for the
812 OpenEmbedded build system in order for it to create your image. You
813 need to get the build environment ready by sourcing an environment
814 setup script (i.e. ``oe-init-build-env``) and you need to be sure two
815 key configuration files are configured appropriately: the
816 ``conf/local.conf`` and the ``conf/bblayers.conf`` file. You must
817 make the OpenEmbedded build system aware of your new layer. See the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600818 ":ref:`dev-manual/common-tasks:enabling your layer`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500819 section in the Yocto Project Development Tasks Manual for information
820 on how to let the build system know about your new layer.
821
822#. *Build the Image:* The OpenEmbedded build system uses the BitBake
823 tool to build images based on the type of image you want to create.
824 You can find more information about BitBake in the
825 :doc:`BitBake User Manual <bitbake:index>`.
826
827 The build process supports several types of images to satisfy
828 different needs. See the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600829 ":ref:`ref-manual/images:Images`" chapter in the Yocto
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500830 Project Reference Manual for information on supported images.
831
832Requirements and Recommendations for Released BSPs
833==================================================
834
835Certain requirements exist for a released BSP to be considered compliant
836with the Yocto Project. Additionally, recommendations also exist. This
837section describes the requirements and recommendations for released
838BSPs.
839
840Released BSP Requirements
841-------------------------
842
843Before looking at BSP requirements, you should consider the following:
844
845- The requirements here assume the BSP layer is a well-formed, "legal"
846 layer that can be added to the Yocto Project. For guidelines on
847 creating a layer that meets these base requirements, see the
848 ":ref:`bsp-guide/bsp:bsp layers`" section in this manual and the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600849 ":ref:`dev-manual/common-tasks:understanding and creating layers`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500850 section in the Yocto Project Development Tasks Manual.
851
852- The requirements in this section apply regardless of how you package
853 a BSP. You should consult the packaging and distribution guidelines
854 for your specific release process. For an example of packaging and
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500855 distribution requirements, see the ":yocto_wiki:`Third Party BSP Release
Andrew Geissler09209ee2020-12-13 08:44:15 -0600856 Process </Third_Party_BSP_Release_Process>`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500857 wiki page.
858
859- The requirements for the BSP as it is made available to a developer
860 are completely independent of the released form of the BSP. For
861 example, the BSP Metadata can be contained within a Git repository
862 and could have a directory structure completely different from what
863 appears in the officially released BSP layer.
864
865- It is not required that specific packages or package modifications
866 exist in the BSP layer, beyond the requirements for general
867 compliance with the Yocto Project. For example, no requirement exists
868 dictating that a specific kernel or kernel version be used in a given
869 BSP.
870
871Following are the requirements for a released BSP that conform to the
872Yocto Project:
873
874- *Layer Name:* The BSP must have a layer name that follows the Yocto
875 Project standards. For information on BSP layer names, see the
876 ":ref:`bsp-guide/bsp:bsp layers`" section.
877
878- *File System Layout:* When possible, use the same directory names in
879 your BSP layer as listed in the ``recipes.txt`` file, which is found
880 in ``poky/meta`` directory of the :term:`Source Directory`
881 or in the OpenEmbedded-Core Layer (``openembedded-core``) at
Andrew Geissler4c19ea12020-10-27 13:52:24 -0500882 https://git.openembedded.org/openembedded-core/tree/meta.
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500883
884 You should place recipes (``*.bb`` files) and recipe modifications
885 (``*.bbappend`` files) into ``recipes-*`` subdirectories by
886 functional area as outlined in ``recipes.txt``. If you cannot find a
887 category in ``recipes.txt`` to fit a particular recipe, you can make
888 up your own ``recipes-*`` subdirectory.
889
890 Within any particular ``recipes-*`` category, the layout should match
891 what is found in the OpenEmbedded-Core Git repository
892 (``openembedded-core``) or the Source Directory (``poky``). In other
893 words, make sure you place related files in appropriately-related
894 ``recipes-*`` subdirectories specific to the recipe's function, or
895 within a subdirectory containing a set of closely-related recipes.
896 The recipes themselves should follow the general guidelines for
897 recipes used in the Yocto Project found in the "`OpenEmbedded Style
898 Guide <http://openembedded.org/wiki/Styleguide>`__".
899
900- *License File:* You must include a license file in the
901 ``meta-bsp_root_name`` directory. This license covers the BSP
902 Metadata as a whole. You must specify which license to use since no
903 default license exists when one is not specified. See the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600904 :yocto_git:`COPYING.MIT </meta-raspberrypi/tree/COPYING.MIT>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500905 file for the Raspberry Pi BSP in the ``meta-raspberrypi`` BSP layer
906 as an example.
907
908- *README File:* You must include a ``README`` file in the
909 ``meta-bsp_root_name`` directory. See the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600910 :yocto_git:`README.md </meta-raspberrypi/tree/README.md>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500911 file for the Raspberry Pi BSP in the ``meta-raspberrypi`` BSP layer
912 as an example.
913
914 At a minimum, the ``README`` file should contain the following:
915
916 - A brief description of the target hardware.
917
918 - A list of all the dependencies of the BSP. These dependencies are
919 typically a list of required layers needed to build the BSP.
920 However, the dependencies should also contain information
921 regarding any other dependencies the BSP might have.
922
923 - Any required special licensing information. For example, this
924 information includes information on special variables needed to
925 satisfy a EULA, or instructions on information needed to build or
926 distribute binaries built from the BSP Metadata.
927
928 - The name and contact information for the BSP layer maintainer.
929 This is the person to whom patches and questions should be sent.
930 For information on how to find the right person, see the
Andrew Geissler09209ee2020-12-13 08:44:15 -0600931 ":ref:`dev-manual/common-tasks:submitting a change to the yocto project`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -0500932 section in the Yocto Project Development Tasks Manual.
933
934 - Instructions on how to build the BSP using the BSP layer.
935
936 - Instructions on how to boot the BSP build from the BSP layer.
937
938 - Instructions on how to boot the binary images contained in the
939 ``binary`` directory, if present.
940
941 - Information on any known bugs or issues that users should know
942 about when either building or booting the BSP binaries.
943
944- *README.sources File:* If your BSP contains binary images in the
945 ``binary`` directory, you must include a ``README.sources`` file in
946 the ``meta-bsp_root_name`` directory. This file specifies exactly
947 where you can find the sources used to generate the binary images.
948
949- *Layer Configuration File:* You must include a ``conf/layer.conf``
950 file in the ``meta-bsp_root_name`` directory. This file identifies
951 the ``meta-bsp_root_name`` BSP layer as a layer to the build
952 system.
953
954- *Machine Configuration File:* You must include one or more
955 ``conf/machine/bsp_root_name.conf`` files in the
956 ``meta-bsp_root_name`` directory. These configuration files define
957 machine targets that can be built using the BSP layer. Multiple
958 machine configuration files define variations of machine
959 configurations that the BSP supports. If a BSP supports multiple
960 machine variations, you need to adequately describe each variation in
961 the BSP ``README`` file. Do not use multiple machine configuration
962 files to describe disparate hardware. If you do have very different
963 targets, you should create separate BSP layers for each target.
964
965 .. note::
966
967 It is completely possible for a developer to structure the working
968 repository as a conglomeration of unrelated BSP files, and to possibly
969 generate BSPs targeted for release from that directory using scripts or
970 some other mechanism (e.g. ``meta-yocto-bsp`` layer). Such considerations
971 are outside the scope of this document.
972
973Released BSP Recommendations
974----------------------------
975
976Following are recommendations for released BSPs that conform to the
977Yocto Project:
978
979- *Bootable Images:* Released BSPs can contain one or more bootable
980 images. Including bootable images allows users to easily try out the
981 BSP using their own hardware.
982
983 In some cases, it might not be convenient to include a bootable
984 image. If so, you might want to make two versions of the BSP
985 available: one that contains binary images, and one that does not.
986 The version that does not contain bootable images avoids unnecessary
987 download times for users not interested in the images.
988
989 If you need to distribute a BSP and include bootable images or build
990 kernel and filesystems meant to allow users to boot the BSP for
991 evaluation purposes, you should put the images and artifacts within a
992 ``binary/`` subdirectory located in the ``meta-bsp_root_name``
993 directory.
994
995 .. note::
996
997 If you do include a bootable image as part of the BSP and the
998 image was built by software covered by the GPL or other open
999 source licenses, it is your responsibility to understand and meet
1000 all licensing requirements, which could include distribution of
1001 source files.
1002
1003- *Use a Yocto Linux Kernel:* Kernel recipes in the BSP should be based
1004 on a Yocto Linux kernel. Basing your recipes on these kernels reduces
1005 the costs for maintaining the BSP and increases its scalability. See
1006 the ``Yocto Linux Kernel`` category in the
1007 :yocto_git:`Source Repositories <>` for these kernels.
1008
1009Customizing a Recipe for a BSP
1010==============================
1011
1012If you plan on customizing a recipe for a particular BSP, you need to do
1013the following:
1014
1015- Create a ``*.bbappend`` file for the modified recipe. For information on using
Andrew Geissler09209ee2020-12-13 08:44:15 -06001016 append files, see the ":ref:`dev-manual/common-tasks:using
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001017 .bbappend files in your layer`" section in the Yocto Project Development
1018 Tasks Manual.
1019
1020- Ensure your directory structure in the BSP layer that supports your
1021 machine is such that the OpenEmbedded build system can find it. See
1022 the example later in this section for more information.
1023
1024- Put the append file in a directory whose name matches the machine's
1025 name and is located in an appropriate sub-directory inside the BSP
1026 layer (i.e. ``recipes-bsp``, ``recipes-graphics``, ``recipes-core``,
1027 and so forth).
1028
1029- Place the BSP-specific files in the proper directory inside the BSP
1030 layer. How expansive the layer is affects where you must place these
1031 files. For example, if your layer supports several different machine
1032 types, you need to be sure your layer's directory structure includes
1033 hierarchy that separates the files according to machine. If your
1034 layer does not support multiple machines, the layer would not have
1035 that additional hierarchy and the files would obviously not be able
1036 to reside in a machine-specific directory.
1037
1038Following is a specific example to help you better understand the
1039process. This example customizes customizes a recipe by adding a
1040BSP-specific configuration file named ``interfaces`` to the
1041``init-ifupdown_1.0.bb`` recipe for machine "xyz" where the BSP layer
1042also supports several other machines:
1043
1044#. Edit the ``init-ifupdown_1.0.bbappend`` file so that it contains the
1045 following: ::
1046
1047 FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
1048
1049 The append file needs to be in the ``meta-xyz/recipes-core/init-ifupdown``
1050 directory.
1051
1052#. Create and place the new ``interfaces`` configuration file in the
1053 BSP's layer here: ::
1054
1055 meta-xyz/recipes-core/init-ifupdown/files/xyz-machine-one/interfaces
1056
1057 .. note::
1058
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001059 If the ``meta-xyz`` layer did not support multiple machines, you would place
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001060 the interfaces configuration file in the layer here: ::
1061
1062 meta-xyz/recipes-core/init-ifupdown/files/interfaces
1063
1064 The :term:`FILESEXTRAPATHS` variable in the append files extends the search
1065 path the build system uses to find files during the build. Consequently, for
1066 this example you need to have the ``files`` directory in the same location as
1067 your append file.
1068
1069BSP Licensing Considerations
1070============================
1071
1072In some cases, a BSP contains separately-licensed Intellectual Property
1073(IP) for a component or components. For these cases, you are required to
1074accept the terms of a commercial or other type of license that requires
1075some kind of explicit End User License Agreement (EULA). Once you accept
1076the license, the OpenEmbedded build system can then build and include
1077the corresponding component in the final BSP image. If the BSP is
1078available as a pre-built image, you can download the image after
1079agreeing to the license or EULA.
1080
1081You could find that some separately-licensed components that are
1082essential for normal operation of the system might not have an
1083unencumbered (or free) substitute. Without these essential components,
1084the system would be non-functional. Then again, you might find that
1085other licensed components that are simply 'good-to-have' or purely
1086elective do have an unencumbered, free replacement component that you
1087can use rather than agreeing to the separately-licensed component. Even
1088for components essential to the system, you might find an unencumbered
1089component that is not identical but will work as a less-capable version
1090of the licensed version in the BSP recipe.
1091
1092For cases where you can substitute a free component and still maintain
1093the system's functionality, the "DOWNLOADS" selection from the
1094"SOFTWARE" tab on the :yocto_home:`Yocto Project Website <>` makes
1095available de-featured BSPs that are completely free of any IP
1096encumbrances. For these cases, you can use the substitution directly and
1097without any further licensing requirements. If present, these fully
1098de-featured BSPs are named appropriately different as compared to the
1099names of their respective encumbered BSPs. If available, these
1100substitutions are your simplest and most preferred options. Obviously,
1101use of these substitutions assumes the resulting functionality meets
1102system requirements.
1103
1104.. note::
1105
1106 If however, a non-encumbered version is unavailable or it provides
1107 unsuitable functionality or quality, you can use an encumbered
1108 version.
1109
1110A couple different methods exist within the OpenEmbedded build system to
1111satisfy the licensing requirements for an encumbered BSP. The following
1112list describes them in order of preference:
1113
1114#. *Use the LICENSE_FLAGS Variable to Define the Recipes that Have Commercial or
1115 Other Types of Specially-Licensed Packages:* For each of those recipes, you can
1116 specify a matching license string in a ``local.conf`` variable named
1117 :term:`LICENSE_FLAGS_WHITELIST`.
1118 Specifying the matching license string signifies that you agree to
1119 the license. Thus, the build system can build the corresponding
1120 recipe and include the component in the image. See the
Andrew Geissler09209ee2020-12-13 08:44:15 -06001121 ":ref:`dev-manual/common-tasks:enabling commercially licensed recipes`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001122 section in the Yocto Project Development Tasks Manual for details on
1123 how to use these variables.
1124
1125 If you build as you normally would, without specifying any recipes in
1126 the ``LICENSE_FLAGS_WHITELIST``, the build stops and provides you
1127 with the list of recipes that you have tried to include in the image
1128 that need entries in the ``LICENSE_FLAGS_WHITELIST``. Once you enter
1129 the appropriate license flags into the whitelist, restart the build
1130 to continue where it left off. During the build, the prompt will not
1131 appear again since you have satisfied the requirement.
1132
1133 Once the appropriate license flags are on the white list in the
1134 ``LICENSE_FLAGS_WHITELIST`` variable, you can build the encumbered
1135 image with no change at all to the normal build process.
1136
1137#. *Get a Pre-Built Version of the BSP:* You can get this type of BSP by
1138 selecting the "DOWNLOADS" item from the "SOFTWARE" tab on the
1139 :yocto_home:`Yocto Project website <>`. You can download BSP tarballs
1140 that contain proprietary components after agreeing to the licensing
1141 requirements of each of the individually encumbered packages as part
1142 of the download process. Obtaining the BSP this way allows you to
1143 access an encumbered image immediately after agreeing to the
1144 click-through license agreements presented by the website. If you
1145 want to build the image yourself using the recipes contained within
1146 the BSP tarball, you will still need to create an appropriate
1147 ``LICENSE_FLAGS_WHITELIST`` to match the encumbered recipes in the
1148 BSP.
1149
1150.. note::
1151
1152 Pre-compiled images are bundled with a time-limited kernel that runs
1153 for a predetermined amount of time (10 days) before it forces the
1154 system to reboot. This limitation is meant to discourage direct
1155 redistribution of the image. You must eventually rebuild the image if
1156 you want to remove this restriction.
1157
1158Creating a new BSP Layer Using the ``bitbake-layers`` Script
1159============================================================
1160
1161The ``bitbake-layers create-layer`` script automates creating a BSP
1162layer. What makes a layer a "BSP layer" is the presence of at least one
1163machine configuration file. Additionally, a BSP layer usually has a
1164kernel recipe or an append file that leverages off an existing kernel
1165recipe. The primary requirement, however, is the machine configuration.
1166
1167Use these steps to create a BSP layer:
1168
1169- *Create a General Layer:* Use the ``bitbake-layers`` script with the
1170 ``create-layer`` subcommand to create a new general layer. For
1171 instructions on how to create a general layer using the
1172 ``bitbake-layers`` script, see the
Andrew Geissler09209ee2020-12-13 08:44:15 -06001173 ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001174 section in the Yocto Project Development Tasks Manual.
1175
1176- *Create a Layer Configuration File:* Every layer needs a layer
1177 configuration file. This configuration file establishes locations for
1178 the layer's recipes, priorities for the layer, and so forth. You can
1179 find examples of ``layer.conf`` files in the Yocto Project
1180 :yocto_git:`Source Repositories <>`. To get examples of what you need
1181 in your configuration file, locate a layer (e.g. "meta-ti") and
1182 examine the
Andrew Geissler09209ee2020-12-13 08:44:15 -06001183 :yocto_git:`local.conf </meta-ti/tree/conf/layer.conf>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001184 file.
1185
1186- *Create a Machine Configuration File:* Create a
1187 ``conf/machine/bsp_root_name.conf`` file. See
Andrew Geissler09209ee2020-12-13 08:44:15 -06001188 :yocto_git:`meta-yocto-bsp/conf/machine </poky/tree/meta-yocto-bsp/conf/machine>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001189 for sample ``bsp_root_name.conf`` files. Other samples such as
Andrew Geissler09209ee2020-12-13 08:44:15 -06001190 :yocto_git:`meta-ti </meta-ti/tree/conf/machine>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001191 and
Andrew Geissler09209ee2020-12-13 08:44:15 -06001192 :yocto_git:`meta-freescale </meta-freescale/tree/conf/machine>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001193 exist from other vendors that have more specific machine and tuning
1194 examples.
1195
1196- *Create a Kernel Recipe:* Create a kernel recipe in
1197 ``recipes-kernel/linux`` by either using a kernel append file or a
1198 new custom kernel recipe file (e.g. ``yocto-linux_4.12.bb``). The BSP
1199 layers mentioned in the previous step also contain different kernel
Andrew Geissler09209ee2020-12-13 08:44:15 -06001200 examples. See the ":ref:`kernel-dev/common:modifying an existing recipe`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001201 section in the Yocto Project Linux Kernel Development Manual for
1202 information on how to create a custom kernel.
1203
1204The remainder of this section provides a description of the Yocto
1205Project reference BSP for Beaglebone, which resides in the
Andrew Geissler09209ee2020-12-13 08:44:15 -06001206:yocto_git:`meta-yocto-bsp </poky/tree/meta-yocto-bsp>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001207layer.
1208
1209BSP Layer Configuration Example
1210-------------------------------
1211
1212The layer's ``conf`` directory contains the ``layer.conf`` configuration
1213file. In this example, the ``conf/layer.conf`` is the following: ::
1214
1215 # We have a conf and classes directory, add to BBPATH
1216 BBPATH .= ":${LAYERDIR}"
1217
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001218 # We have a recipes directory containing .bb and .bbappend files, add to BBFILES
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001219 BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
1220 ${LAYERDIR}/recipes-*/*/*.bbappend"
1221
1222 BBFILE_COLLECTIONS += "yoctobsp"
1223 BBFILE_PATTERN_yoctobsp = "^${LAYERDIR}/"
1224 BBFILE_PRIORITY_yoctobsp = "5"
1225 LAYERVERSION_yoctobsp = "4"
1226 LAYERSERIES_COMPAT_yoctobsp = "&DISTRO_NAME_NO_CAP;"
1227
1228The variables used in this file configure the layer. A good way to learn about layer
1229configuration files is to examine various files for BSP from the
1230:yocto_git:`Source Repositories <>`.
1231
1232For a detailed description of this particular layer configuration file,
Andrew Geissler09209ee2020-12-13 08:44:15 -06001233see ":ref:`step 3 <dev-manual/common-tasks:creating your own layer>`"
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001234in the discussion that describes how to create layers in the Yocto
1235Project Development Tasks Manual.
1236
1237BSP Machine Configuration Example
1238---------------------------------
1239
1240As mentioned earlier in this section, the existence of a machine
1241configuration file is what makes a layer a BSP layer as compared to a
1242general or kernel layer.
1243
1244One or more machine configuration files exist in the
1245``bsp_layer/conf/machine/`` directory of the layer: ::
1246
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001247 bsp_layer/conf/machine/machine1\.conf
1248 bsp_layer/conf/machine/machine2\.conf
1249 bsp_layer/conf/machine/machine3\.conf
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001250 ... more ...
1251
1252For example, the machine configuration file for the `BeagleBone and
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001253BeagleBone Black development boards <https://beagleboard.org/bone>`__ is
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001254located in the layer ``poky/meta-yocto-bsp/conf/machine`` and is named
1255``beaglebone-yocto.conf``: ::
1256
1257 #@TYPE: Machine
1258 #@NAME: Beaglebone-yocto machine
1259 #@DESCRIPTION: Reference machine configuration for http://beagleboard.org/bone and http://beagleboard.org/black boards
1260
1261 PREFERRED_PROVIDER_virtual/xserver ?= "xserver-xorg"
1262 XSERVER ?= "xserver-xorg \
1263 xf86-video-modesetting \
1264 "
1265
1266 MACHINE_EXTRA_RRECOMMENDS = "kernel-modules kernel-devicetree"
1267
1268 EXTRA_IMAGEDEPENDS += "u-boot"
1269
1270 DEFAULTTUNE ?= "cortexa8hf-neon"
1271 include conf/machine/include/tune-cortexa8.inc
1272
1273 IMAGE_FSTYPES += "tar.bz2 jffs2 wic wic.bmap"
1274 EXTRA_IMAGECMD_jffs2 = "-lnp "
1275 WKS_FILE ?= "beaglebone-yocto.wks"
1276 IMAGE_INSTALL_append = " kernel-devicetree kernel-image-zimage"
1277 do_image_wic[depends] += "mtools-native:do_populate_sysroot dosfstools-native:do_populate_sysroot"
1278
1279 SERIAL_CONSOLES ?= "115200;ttyS0 115200;ttyO0"
1280 SERIAL_CONSOLES_CHECK = "${SERIAL_CONSOLES}"
1281
1282 PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
1283 PREFERRED_VERSION_linux-yocto ?= "5.0%"
1284
1285 KERNEL_IMAGETYPE = "zImage"
1286 KERNEL_DEVICETREE = "am335x-bone.dtb am335x-boneblack.dtb am335x-bonegreen.dtb"
1287 KERNEL_EXTRA_ARGS += "LOADADDR=${UBOOT_ENTRYPOINT}"
1288
1289 SPL_BINARY = "MLO"
1290 UBOOT_SUFFIX = "img"
1291 UBOOT_MACHINE = "am335x_evm_defconfig"
1292 UBOOT_ENTRYPOINT = "0x80008000"
1293 UBOOT_LOADADDRESS = "0x80008000"
1294
1295 MACHINE_FEATURES = "usbgadget usbhost vfat alsa"
1296
1297 IMAGE_BOOT_FILES ?= "u-boot.${UBOOT_SUFFIX} MLO zImage am335x-bone.dtb am335x-boneblack.dtb am335x-bonegreen.dtb"
1298
1299The variables used to configure the machine define machine-specific properties; for
1300example, machine-dependent packages, machine tunings, the type of kernel
1301to build, and U-Boot configurations.
1302
1303The following list provides some explanation for the statements found in
1304the example reference machine configuration file for the BeagleBone
1305development boards. Realize that much more can be defined as part of a
1306machine's configuration file. In general, you can learn about related
1307variables that this example does not have by locating the variables in
Andrew Geissler09209ee2020-12-13 08:44:15 -06001308the ":ref:`ref-manual/variables:variables glossary`" in the Yocto
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001309Project Reference Manual.
1310
1311- :term:`PREFERRED_PROVIDER_virtual/xserver <PREFERRED_PROVIDER>`:
1312 The recipe that provides "virtual/xserver" when more than one
1313 provider is found. In this case, the recipe that provides
1314 "virtual/xserver" is "xserver-xorg", which exists in
1315 ``poky/meta/recipes-graphics/xorg-xserver``.
1316
1317- :term:`XSERVER`: The packages that
1318 should be installed to provide an X server and drivers for the
1319 machine. In this example, the "xserver-xorg" and
1320 "xf86-video-modesetting" are installed.
1321
1322- :term:`MACHINE_EXTRA_RRECOMMENDS`:
1323 A list of machine-dependent packages not essential for booting the
1324 image. Thus, the build does not fail if the packages do not exist.
1325 However, the packages are required for a fully-featured image.
1326
1327 .. tip::
1328
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001329 Many ``MACHINE*`` variables exist that help you configure a particular piece
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001330 of hardware.
1331
1332- :term:`EXTRA_IMAGEDEPENDS`:
1333 Recipes to build that do not provide packages for installing into the
1334 root filesystem but building the image depends on the recipes.
1335 Sometimes a recipe is required to build the final image but is not
1336 needed in the root filesystem. In this case, the U-Boot recipe must
1337 be built for the image.
1338
1339- :term:`DEFAULTTUNE`: Machines
1340 use tunings to optimize machine, CPU, and application performance.
1341 These features, which are collectively known as "tuning features",
1342 exist in the :term:`OpenEmbedded-Core (OE-Core)` layer (e.g.
1343 ``poky/meta/conf/machine/include``). In this example, the default
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001344 tuning file is "cortexa8hf-neon".
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001345
1346 .. note::
1347
1348 The include statement that pulls in the
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001349 ``conf/machine/include/tune-cortexa8.inc`` file provides many tuning
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001350 possibilities.
1351
1352- :term:`IMAGE_FSTYPES`: The
1353 formats the OpenEmbedded build system uses during the build when
1354 creating the root filesystem. In this example, four types of images
1355 are supported.
1356
1357- :term:`EXTRA_IMAGECMD`:
1358 Specifies additional options for image creation commands. In this
1359 example, the "-lnp " option is used when creating the
1360 `JFFS2 <https://en.wikipedia.org/wiki/JFFS2>`__ image.
1361
1362- :term:`WKS_FILE`: The location of
Andrew Geissler09209ee2020-12-13 08:44:15 -06001363 the :ref:`Wic kickstart <ref-manual/kickstart:openembedded kickstart (\`\`.wks\`\`) reference>` file used
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001364 by the OpenEmbedded build system to create a partitioned image
1365 (image.wic).
1366
1367- :term:`IMAGE_INSTALL`:
1368 Specifies packages to install into an image through the
1369 :ref:`image <ref-classes-image>` class. Recipes
1370 use the ``IMAGE_INSTALL`` variable.
1371
1372- ``do_image_wic[depends]``: A task that is constructed during the
1373 build. In this example, the task depends on specific tools in order
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001374 to create the sysroot when building a Wic image.
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001375
1376- :term:`SERIAL_CONSOLES`:
1377 Defines a serial console (TTY) to enable using getty. In this case,
1378 the baud rate is "115200" and the device name is "ttyO0".
1379
1380- :term:`PREFERRED_PROVIDER_virtual/kernel <PREFERRED_PROVIDER>`:
1381 Specifies the recipe that provides "virtual/kernel" when more than
1382 one provider is found. In this case, the recipe that provides
1383 "virtual/kernel" is "linux-yocto", which exists in the layer's
1384 ``recipes-kernel/linux`` directory.
1385
1386- :term:`PREFERRED_VERSION_linux-yocto <PREFERRED_VERSION>`:
1387 Defines the version of the recipe used to build the kernel, which is
1388 "5.0" in this case.
1389
1390- :term:`KERNEL_IMAGETYPE`:
1391 The type of kernel to build for the device. In this case, the
1392 OpenEmbedded build system creates a "zImage" image type.
1393
1394- :term:`KERNEL_DEVICETREE`:
1395 The names of the generated Linux kernel device trees (i.e. the
1396 ``*.dtb``) files. All the device trees for the various BeagleBone
1397 devices are included.
1398
1399- :term:`KERNEL_EXTRA_ARGS`:
1400 Additional ``make`` command-line arguments the OpenEmbedded build
1401 system passes on when compiling the kernel. In this example,
1402 ``LOADADDR=${UBOOT_ENTRYPOINT}`` is passed as a command-line argument.
1403
1404- :term:`SPL_BINARY`: Defines the
1405 Secondary Program Loader (SPL) binary type. In this case, the SPL
1406 binary is set to "MLO", which stands for Multimedia card LOader.
1407
1408 The BeagleBone development board requires an SPL to boot and that SPL
1409 file type must be MLO. Consequently, the machine configuration needs
1410 to define ``SPL_BINARY`` as ``MLO``.
1411
1412 .. note::
1413
Andrew Geissler4c19ea12020-10-27 13:52:24 -05001414 For more information on how the SPL variables are used, see the
Andrew Geissler09209ee2020-12-13 08:44:15 -06001415 :yocto_git:`u-boot.inc </poky/tree/meta/recipes-bsp/u-boot/u-boot.inc>`
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001416 include file.
1417
1418- :term:`UBOOT_* <UBOOT_ENTRYPOINT>`: Defines
1419 various U-Boot configurations needed to build a U-Boot image. In this
1420 example, a U-Boot image is required to boot the BeagleBone device.
1421 See the following variables for more information:
1422
1423 - :term:`UBOOT_SUFFIX`:
1424 Points to the generated U-Boot extension.
1425
1426 - :term:`UBOOT_MACHINE`:
1427 Specifies the value passed on the make command line when building
1428 a U-Boot image.
1429
1430 - :term:`UBOOT_ENTRYPOINT`:
1431 Specifies the entry point for the U-Boot image.
1432
1433 - :term:`UBOOT_LOADADDRESS`:
1434 Specifies the load address for the U-Boot image.
1435
1436- :term:`MACHINE_FEATURES`:
1437 Specifies the list of hardware features the BeagleBone device is
1438 capable of supporting. In this case, the device supports "usbgadget
1439 usbhost vfat alsa".
1440
1441- :term:`IMAGE_BOOT_FILES`:
1442 Files installed into the device's boot partition when preparing the
1443 image using the Wic tool with the ``bootimg-partition`` or
1444 ``bootimg-efi`` source plugin.
1445
1446BSP Kernel Recipe Example
1447-------------------------
1448
1449The kernel recipe used to build the kernel image for the BeagleBone
1450device was established in the machine configuration: ::
1451
1452 PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
1453 PREFERRED_VERSION_linux-yocto ?= "5.0%"
1454
1455The ``meta-yocto-bsp/recipes-kernel/linux`` directory in the layer contains
1456metadata used to build the kernel. In this case, a kernel append file
1457(i.e. ``linux-yocto_5.0.bbappend``) is used to override an established
1458kernel recipe (i.e. ``linux-yocto_5.0.bb``), which is located in
Andrew Geissler09209ee2020-12-13 08:44:15 -06001459:yocto_git:`/poky/tree/meta/recipes-kernel/linux`.
Andrew Geisslerc9f78652020-09-18 14:11:35 -05001460
1461Following is the contents of the append file: ::
1462
1463 KBRANCH_genericx86 = "v5.0/standard/base"
1464 KBRANCH_genericx86-64 = "v5.0/standard/base"
1465 KBRANCH_edgerouter = "v5.0/standard/edgerouter"
1466 KBRANCH_beaglebone-yocto = "v5.0/standard/beaglebone"
1467
1468 KMACHINE_genericx86 ?= "common-pc"
1469 KMACHINE_genericx86-64 ?= "common-pc-64"
1470 KMACHINE_beaglebone-yocto ?= "beaglebone"
1471
1472 SRCREV_machine_genericx86 ?= "3df4aae6074e94e794e27fe7f17451d9353cdf3d"
1473 SRCREV_machine_genericx86-64 ?= "3df4aae6074e94e794e27fe7f17451d9353cdf3d"
1474 SRCREV_machine_edgerouter ?= "3df4aae6074e94e794e27fe7f17451d9353cdf3d"
1475 SRCREV_machine_beaglebone-yocto ?= "3df4aae6074e94e794e27fe7f17451d9353cdf3d"
1476
1477 COMPATIBLE_MACHINE_genericx86 = "genericx86"
1478 COMPATIBLE_MACHINE_genericx86-64 = "genericx86-64"
1479 COMPATIBLE_MACHINE_edgerouter = "edgerouter"
1480 COMPATIBLE_MACHINE_beaglebone-yocto = "beaglebone-yocto"
1481
1482 LINUX_VERSION_genericx86 = "5.0.3"
1483 LINUX_VERSION_genericx86-64 = "5.0.3"
1484 LINUX_VERSION_edgerouter = "5.0.3"
1485 LINUX_VERSION_beaglebone-yocto = "5.0.3"
1486
1487This particular append file works for all the machines that are
1488part of the ``meta-yocto-bsp`` layer. The relevant statements are
1489appended with the "beaglebone-yocto" string. The OpenEmbedded build
1490system uses these statements to override similar statements in the
1491kernel recipe:
1492
1493- :term:`KBRANCH`: Identifies the
1494 kernel branch that is validated, patched, and configured during the
1495 build.
1496
1497- :term:`KMACHINE`: Identifies the
1498 machine name as known by the kernel, which is sometimes a different
1499 name than what is known by the OpenEmbedded build system.
1500
1501- :term:`SRCREV`: Identifies the
1502 revision of the source code used to build the image.
1503
1504- :term:`COMPATIBLE_MACHINE`:
1505 A regular expression that resolves to one or more target machines
1506 with which the recipe is compatible.
1507
1508- :term:`LINUX_VERSION`: The
1509 Linux version from kernel.org used by the OpenEmbedded build system
1510 to build the kernel image.