Guideline to create OEM specific images

All the work needs be done only in the meta-rdk-oem layer

Write a recipe <oem>-image-tools-native.bb under recipes-tools to copy all the tools, binaries and scripts needed to create custom oem image to the staging binary directory

• • This recipe should fetch all the sources from the GIT repo
  • Example name space for the GIT repo where you should place all the tools like permission files, authentication keys etc - “rdk/devices/<OEM>/<OEM_device>/tools”
• • Example namespace for the GIT repo to keep all the binaries (crcsum etc) - “rdk/devices/<OEM>/<OEM_device>/bin”
  • This recipe will have only one task – do_install, which copies all the necessary files to create oem images to staging binary directory
  • "inherit native" this class would short-circuit all the target build and strip tasks.

Write a bbclass - oem-image.bbclass 

• • Add oem-image-tools as DEPENDS
  • In this class add a task "create_oem_image" to create the oem specific images - "addtask create_oem_image after do_rootfs before do_build"
  • Copy all the tools and files needed from STAGING_BINDIR_NATIVE to working directory, which were copied by <oem>-image-tools-native.bb
  • Once copied this task will have the logic to create the custom oem images
  • After creating the custom oem images, copy them to DEPLOY_DIR_IMAGE
  • In recipe add "create_oem_image[nostamp] = "1"", this allows task to run every-time on every run of bitbake.
  • Add create_oem_image[depends] += "${PN}:do_rootfs" to make sure the do_rootfs task is re-run every time before executing the task - create_oem_image.
  • Make this class inherit by all the rdk image recipes,
     rdk-generic-mediaserver-image.bbappend: inherit oem-image,comcast-mediaclient-image.bbappend:inherit oem-image,comcast-hybrid-image.bbappend:inherit oem-image,rdk-generic-hybrid-image.bbappend:inherit oem-image, core-image-minimal.bbappend:inherit oem-image,rdk-generic-image.bbappend:inherit oem-image,rdk-generic-mediaclient-image.bbappend:inherit oem-image.

Adding a new SoC/OEM to RDK

Adding a new machine to the Yocto Project is a straightforward process which involves following steps:

• Create a new layer which will hold all the recipes and machine configurations for the new SoC/OEM.
• Adding the Machine Configuration File for the new SoC/OEM.
• Adding a Kernel for the Machine.
• Adding Recipe for SoC/OEM
• Creating packages for building images

Creating the new SoC/OEM Layer

Use the yocto-layer create sub-command to create a new general layer.

•  yocto-layer create mylayer

There shall be separate device (machine)  configuration file (.conf) for each device for the particular chip family for which the layer is intended for

• For Eg : A layer "meta-rdk-oem-OEM-X-SOC-Y" means this layer shall be able to build any devices manufactured by  OEM "X" with all variants of SoC "Y" like Y-1,Y-2 etc

The device (machine) configuration file shall include corresponding include (.inc) file to get machine configuration details.

Adding the Machine Configuration File

To add a machine configuration, you need to add a .conf file with details of the device being added to the conf/machine/ file.
The most important variables to set in this file are as follows:

• TARGET_ARCH (e.g. "arm")
• PREFERRED_PROVIDER_virtual/kernel 
• MACHINE_FEATURES (e.g. "apm screen wifi")

You might also need these variables:

• KERNEL_IMAGETYPE (e.g. "zImage")
• IMAGE_FSTYPES (e.g. "tar.gz jffs2")

The default configuration are defined in meta-rdk/conf/distro/rdk.conf and it should be overwritten by the machine specific conf file.
For example, meta-rdk-oem-<>/meta-<>/conf/machine/include/<>.inc

• PREFERRED_PROVIDER_virtual/iarmmgrs-hal = "iarmmgrs-hal-broadcom"
• PREFERRED_PROVIDER_virtual/closedcaption-hal = "closedcaption-hal-broadcom"

Adding a Kernel for the Machine

The OpenEmbedded build system needs to be able to build a kernel for the machine. We need to either create a new kernel recipe for this machine, or extend an existing recipe. There are several kernel examples in the Source Directory at meta/recipes-kernel/linux that can be used as references.
If you are creating a new recipe, following steps need to be done:

• setting up a SRC_URI.
• Specify any necessary patches
• create a configure task that configures the unpacked kernel with a defconfig.

If you are extending an existing kernel, it is usually a matter of adding a suitable defconfig file. The file needs to be added into a location similar to defconfig files used for other machines in a given kernel.
A possible way to do this is by listing the file in the SRC_URI and adding the machine to the expression in COMPATIBLE_MACHINE:

• COMPATIBLE_MACHINE = '(qemux86|qemumips)'

Adding recipes for SoC/OEM

The following kind of recipes can be added to SoC/OEM layer. The recipes shall be grouped as described in slide “BSP Reference Layer”

• recipes (.bb) to build Kernel
• recipes(.bb)  to build SDK
• Kernel patches (SoC/OEM specific - if any)
• SDK patches (SoC/OEM specific - if any)
• Any SoC/OEM specific scripts or files which need to be installed in RFS

Creating packages for building images

Create a custom package-group for the SoC/OEM which shall list all the recipes that are required for this image. For example, for the hybrid box the following recipe can be appended to the mediaserver package group.

• meta-rdk-soc-broadcom/meta-brcm/recipes-core/packagegroups/packagegroup-rdk-mediaserver.bbappend : 
  RDEPENDS_packagegroup-rdk-generic-mediaserver += "\
      gstqamtunersrc-brcm \
  "

Create a custom image for generating RFS for required SoC/OEM. For example,

• meta-rdk-<soc>/recipes-core/images/<soc>-hybrid-image.bb
  IMAGE_INSTALL += "\
      packagegroup-rdk-baserootfs \
      packagegroup-rdk-<soc/oem specific packages> \
  "

Different kind of build and configuration available in RDK

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