Add a Yocto Layer to a PetaLinux Project and Build a Recipe in the Layer with PetaLinux Tools

xilinx_logo_1

This post shows how to add a new Yocto layer to your PetaLinux project and build a recipe in the Yocto layer with PetaLinux Tools 2017.4.

This post uses the “meta-example” from DynamicDevices.

Prerequisites

Download and Install Xilinx’s 2017.4 PetaLinux Tools at link

Post Updates

May 4th 2018

These instructions don’t cover creating a layer, they cover pulling in an existing layer.

April 25th 2018

Updated the example to use ${PROOT} instead of an absolute path when entering the user layer into the config field. Using ${PROOT} in the user layer path allows you to support running petalinux-build immediately after unpacking a PetaLinux project. Without ${PROOT}, the user is required to run petalinux-config after unpacking a PetaLinux project.

Motivation

In Yocto new layers are added to BBLAYERS listed in conf/bblayers.conf. PetaLinux Tools 2017.4 creates this file and says not to edit it:

# WARNING: this configuration has been automatically generated and in
# most cases should not be edited. If you need more flexibility than
# this configuration provides, it is strongly suggested that you set
# up a proper instance of the full build system and use that instead.

It doesn’t work to disregard the warning, edit this file and run petalinux-config to pick up the layer because PetaLinux Tools will regenerate it during petalinux-config.

This write up shows the correct way to add a layer to BBLAYERS in conf/bblayers.conf using PetaLinux Tools 2017.4.

Check Out the Layer and Put it in the Right Spot

1. cd into your PetaLinux project

2. make and cd into components/ext_source

mkdir -p components/ext_source
cd components/ext_source

You should put your external source here according to Table A-1 on p89 of the PetaLinux Tools reference guide.

3. Get source with:

git clone https://github.com/DynamicDevices/meta-example

Add a layer to BBLAYERS in conf/bblayers.conf

1. cd into your PetaLinux project

2. Type:

petalinux-config

After a few seconds the misc/config System Configuration menu will appear:

misc_config_system_configuration_2

3. Press down until the cursor is on Yocto Settings —> and hit Enter.

yocto_settings_3

After hitting Enter you should see:

yocto_settings_menu_4

4. Press down until the cursor is on User Layers —> and hit Enter.

user_layers_5

After hitting Enter you will see:

user_layers_settings_6

5. Press Enter.

You should see the following:

user_layer_0_7

6. Enter the full path to meta-example:

enter_full_path_to_meta_example_8

Note: you should use ${PROOT}. ${PROOT} is also used in TMPDIR (${PROOT}/build/tmp).

…and hit Enter to Ok

You should see:

confirm_adding_user_layer_9

If you want to enter in another layer scroll down to user layer 1, hit enter, enter the path…etc.

You can enter up-to 10 user layers.

7. Select Exit:

exit_user_layer_10

…Exit:

exit_yocto_settings_11

…Exit:

exit_misc_config_system_configuration_12

…and to save the configuration:

save_new_configuration_13

After these steps the following update gets made to the project (that are not .gitignored):

diff --git a/project-spec/configs/config b/project-spec/configs/config
index 0914524..fdc4d1f 100644
--- a/project-spec/configs/config
+++ b/project-spec/configs/config
@@ -255,5 +255,6 @@ CONFIG_YOCTO_NETWORK_SSTATE_FEEDS_URL="http://petalinux.xilinx.com/sswreleases/r
 #
 # User Layers
 #
-CONFIG_USER_LAYER_0=""
+CONFIG_USER_LAYER_0="/home/pfefferz/plprjs4/mtd_board/components/ext_source/meta-example"
+CONFIG_USER_LAYER_1=""
 CONFIG_SUBSYSTEM_BOOTARGS_GENERATED="earlycon clk_ignore_unused"

In addition conf/bblayers.conf now contains meta-example:

pfefferz@plc2:~/plprjs4/mtd_board$ cat build/conf/bblayers.conf 
# WARNING: this configuration has been automatically generated and in
# most cases should not be edited. If you need more flexibility than
# this configuration provides, it is strongly suggested that you set
# up a proper instance of the full build system and use that instead.

LCONF_VERSION = "7"

BBPATH = "${TOPDIR}"
SDKBASEMETAPATH = "/home/pfefferz/tools/opt/pkg/petalinux/components/yocto/source/aarch64"
BBLAYERS := " \
  ${SDKBASEMETAPATH}/layers/core/meta \
  ${SDKBASEMETAPATH}/layers/core/meta-poky \
  ${SDKBASEMETAPATH}/layers/meta-perl \
  ${SDKBASEMETAPATH}/layers/meta-systemd \
  ${SDKBASEMETAPATH}/layers/meta-gpe \
  ${SDKBASEMETAPATH}/layers/meta-python \
  ${SDKBASEMETAPATH}/layers/meta-efl \
  ${SDKBASEMETAPATH}/layers/meta-ruby \
  ${SDKBASEMETAPATH}/layers/meta-filesystems \
  ${SDKBASEMETAPATH}/layers/meta-gnome \
  ${SDKBASEMETAPATH}/layers/meta-multimedia \
  ${SDKBASEMETAPATH}/layers/meta-networking \
  ${SDKBASEMETAPATH}/layers/meta-webserver \
  ${SDKBASEMETAPATH}/layers/meta-xfce \
  ${SDKBASEMETAPATH}/layers/meta-initramfs \
  ${SDKBASEMETAPATH}/layers/meta-oe \
  ${SDKBASEMETAPATH}/layers/meta-linaro-toolchain \
  ${SDKBASEMETAPATH}/layers/meta-qt5 \
  ${SDKBASEMETAPATH}/layers/meta-xilinx \
  ${SDKBASEMETAPATH}/layers/meta-xilinx-tools \
  ${SDKBASEMETAPATH}/layers/meta-petalinux \
  ${SDKBASEMETAPATH}/layers/meta-virtualization \
  ${SDKBASEMETAPATH}/layers/meta-openamp \
  ${SDKBASEMETAPATH}/workspace \
  /home/pfefferz/plprjs4/mtd_board/project-spec/meta-plnx-generated \
  /home/pfefferz/plprjs4/mtd_board/project-spec/meta-user \
  /home/pfefferz/plprjs4/mtd_board/components/ext_source/meta-example \

Note: ${PROOT} gets turned into /home/pfefferz/plprjs4/mtd_board in this case.

Build a Recipe from meta-example with PetaLinux Tools

1. Open project-spec/meta-user/recipes-core/images/petalinux-image.bbappend and add IMAGE_INSTALL_append = “ bbexample”

The space between “ and bbexample” this is required.

add_image_install_append_bbexample_14

Note: there is a very brief section in the PetaLinux Tools reference guide called Adding a Recipe from Yocto e-SDK Layers topetalinux-image-full.bb on page 81 that gives the location of the file (project-spec/meta-user/recipes-core/images/petalinux-image.bbappend) that has to be edited.

2. Run:

petalinux-config -c rootfs

You should see:

configuration_menu_15

3. Arrow down to user packages —>:

arrow_to_user_packages_16

…and hit Enter. You should see:

bbexample_added_17

4. Type ‘Y’. You’ll see:

bbexample_activated_18

5. Hit Exit, Exit then Yes to save.

You’ll see the following difference in project-spec/configs/rootfs_config

--- a/project-spec/configs/rootfs_config
+++ b/project-spec/configs/rootfs_config
@@ -4379,6 +4379,7 @@ CONFIG_bridge-utils=y
 #
 # user packages 
 #
+CONFIG_bbexample=y

In addition ./project-spec/meta-plnx-generated/recipes-core/images/petalinux-user-image.bb gets generated:

new_command_generated_19

6. Now type:

petalinux-build

You should see:

build_start_20

…and something like the following if everything built okay:

build_start_21

root@mtd_board:~# bbexample 
Hello Yocto World...
Hello World (from a shared library!)

6. After booting your target, run bbexample:

Find where its located:

root@mtd_board:~# which bbexample
/usr/bin/bbexample

Also find the lib:

root@mtd_board:~# LD_DEBUG=libs bbexample
      2131:     find library=libbbexample.so.1 [0]; searching
      2131:      search cache=/etc/ld.so.cache
      2131:       trying file=/usr/lib/libbbexample.so.1
      2131:
      2131:     find library=libc.so.6 [0]; searching
      2131:      search cache=/etc/ld.so.cache
      2131:       trying file=/lib/libc.so.6
      2131:
      2131:
      2131:     calling init: /lib/libc.so.6
      2131:
      2131:
      2131:     calling init: /usr/lib/libbbexample.so.1
      2131:
      2131:
      2131:     initialize program: bbexample
      2131:
      2131:
      2131:     transferring control: bbexample
      2131:
Hello Yocto World...
Hello World (from a shared library!)
      2131:
      2131:     calling fini: bbexample [0]
      2131:
      2131:
      2131:     calling fini: /usr/lib/libbbexample.so.1 [0]
      2131:
root@mtd_board:~#

Note on the Yocto Version used in PetaLinux Tools 2017.4

PetaLinux Tools 2017.4 is based on the 2.2.3 “Morty” release of the Yocto Project. See the release notes @ link for details.

If you check out Morty and diff it with the release you will see 928 lines added from the morty branch and 1494 lines removed.

Here are the commands to run through the calc:

git clone git://git.yoctoproject.org/poky
pushd poky
git checkout morty
popd
diff -ur poky ~/tools/opt/pkg/petalinux/components/yocto/source/aarch64/layers/core | grep -E "^\+" | wc -l
diff -ur poky ~/tools/opt/pkg/petalinux/components/yocto/source/aarch64/layers/core | grep -E "^-" | wc -l

References

  • meta_example

  • Yocto

  • Yocto docs

  • Yocto Project Mega-Manual Morty 2.2.3 PDF @ link

  • See 5.1 Understanding and Creating Layers for a discussion about layers (p37/400)

  • Yocto Project Mega-Manual Rocko 2.4.2 PDF @ link

  • Yocto Source Repositories @ link

  • Building your own recipes from first principles @ link

  • Xilinx

  • PetaLinux Tools 2017.4 Reference Guide UG1144 (v2017.4) December 20, 2017 @ link