Creating our own meta layer & creating a custom helloworld application and adding it to our project using yocto

 Hello All,

In my previous article we have seen that how to construct an embedded linux image for "qemux86-64" and verify its booting.

In case if you have missed it, here is the link: https://learnyoctowithme.blogspot.com/2022/04/constructing-embedded-linux-image-for.html

In this article we are going to see how we can create our own layer and adding it to our project using yocto

pre-requisite: You need to be familiar with my previous article as it shows the image construction and setting up the build environment

link : https://www.blogger.com/blog/posts/8695339245532547417?tab=rj

what is a layer?

Layer is nothing but a logical collection of related recipes

Types of Layers: oe-core, BSP Layer, application layer

Layer name starts with meta-, but this is not a technical restriction.

Eg. meta-mylayer

creating our own meta layer(meta-mylayer) using yocto project:

step 1: source the environment 

$  source ./oe-init-build-env build_x86

step 2: Inside build_x86 folder, run the command

$ bitbake-layers add-layer /home/shashank/poky/meta-mylayer

NOTE: This will create a new folder called "meta-mylayer" in poky directory

step 3: switch to meta-mylayer directory

$ cd ../poky/meta-mylayer

Inside meta-mylayer directory we can see folders called conf and recipes-example

conf folder consists of layer configuration file as seen below

recipes-example folder consists of example folder and in example folder we can find example_0.1.bb file 

 

step 4: meta-mylayer is already added to your bblayer.conf file, to view it use command

$ bitbake-layers show-layers

step 5: now check your layer compatibility using command

$ yocto-check-layer ../meta-mylayer 

creating a sample hello world.c application and integrating it to our rootfs:

step 1:  Inside meta-mylayer folder, there is a folder named recipes-example and inside recipes-example folder there is a folder called example 

$ cd poky/meta-mylayer/recipes-examples/example 

step 2: create a folder named files inside example folder

$ mkdir files

step 3: switch to files folder and create a file called helloworld.c

$ vi helloworld.c

step 4:  switch back to example folder

$ cd ..

step 5: now create a file called helloworld_0.1.bb  with below content

$ vi helloworld_0.1.bb 

step 6: now compile the helloworld recipe using

$ bitbake helloworld

Now your helloworld recipe has been successfully compiled using bitbake

step 7: now add helloworld package to our image

switch to build_x86 folder

$ cd ../../../build_x86

open the local.conf file

$ vi conf/local.conf

append the line IMAGE_INSTALL_append +="helloworld"

step 8: now compile the image as

$ bitbake core-image-minimal

now image compilation has been successful

step 9: now boot the image using qemu

$ runqemu nographic

step 10: after image booted, run the command to verify the helloworld application

$ helloworld

Thats it we have successfully integrated our helloworld application to our rootfs.