How to include a simple C file in Yocto image by creating your own layer?

In this post, I will explain about creating your own layer in Yocto and then creating a simple C file which gets included in your final image(core-image-minimal).

So, first we will understand how to create your own layer in Yocto and then adding a simple C application into an final image.

Create your own layer

Basically there are two ways to create your own layer in Yocto:

1. Manually 
2. through Bitbake script

I will create a layer through Bitbake which is quite simpler and easier than doing it manually.

Assuming you have poky project downloaded from yocto's website, 

• Navigate to poky project and set environment by running source oe-init-build-env
• Now you got moved to "Build" directory, if you want to create a layer where other defaults layers(e.g. meta-poky etc.) are present then run "cd .."
• Create a layer by running "bitbake-layers create-layer <meta-newlayer>" 
• Navigate to build directory and run "bitbake-layers add-layer ../<meta-newlayer> which adds this layer into bblayer.conf file
• That's it !! see below screenshot for reference,

Create a simple C app and recipe

Now we will create a simple C application and a recipe. A recipe is parsed to Bitbake and Bitbake further built this C app, installed onto a final image. Follow below steps:

• Navigate to your own layer - cd meta-love
• Create a recipe - mkdir recipes-love
• Navigate to recipe dir and create a app dir - cd recipes-love & mkdir love
• Navigate to app dir - cd love
• Create another dir called files - mkdir files
• Create a recipe with following content - vi love_0.1.bb

          SUMMARY = "Test Application"

          LICENSE = "CLOSED"

          SRC_URI = "file://love.c \

       "

          do_compile () {

          ${CC} ${CFLAGS} ${LDFLAGS} ${WORKDIR}/love.c -o ${WORKDIR}/love

          }

          do_install () {

         install -d ${D}${bindir}

         install -m 0755 ${WORKDIR}/love ${D}${bindir}/

          }

• Navigate to files dir - cd files
• Create a simple C file - vi love.c

          int main()

          {

              printf("Love is God\n");

              return 0;

          }

• Add IMAGE_INSTALL_append = " love" in build/conf/local.conf file 
• Navigate to build and run "bitbake core-image-minimal" (Make sure, you have set environment)
• Go to "build/tmp/deploy/images/qemux86" and run "runqemu core-image-minimal"
• Run your app