View source for Modify the linux kernel with configuration fragments in Yocto

== Modify the linux kernel with configuration fragments in Yocto ==

Modifying the kernel configuration in Yocto may be different depending on the original conditions.

In general would be convenient to adopt '''configuration fragments''' that can be generated directly with the
bitbake command executing the following steps:

1. Prepare for the kernel configuration (take a snapshot)

 bitbake -c kernel_configme virtual/kernel

2. Edit the configuration (do your modifications)

 bitbake -c menuconfig virtual/kernel

3. Save the configuration differences (extract the differences)

 bitbake -c diffconfig virtual/kernel

The differences will be saved in '''$WORKDIR/fragment.cfg'''

You have to copy the '''$WORKDIR/fragment.cfg''' in your layer directory and in the recipe (bbappend) as in the example below.


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'''Examples'''

This is an example of the files involved in this operation

 meta-training
 └── recipes-kernel
     └── linux
         ├── linux-intel
         │   └── koan-modified-configuration.cfg
         └── linux-intel_%.bbappend


Content of '''linux-intel_%.bbappend'''

 FILESEXTRAPATHS_prepend := "${THISDIR}/linux-intel:"
 SRC_URI += "file://koan-modified-configuration.cfg"


Content of '''linux-intel/koan-modified-configuration.cfg'''

 CONFIG_SOUND=y
 # CONFIG_USB_AUDIO is not set
 # CONFIG_USB_MIDI_GADGET is not set


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''Note: After integrating configuration fragments into the appended recipe, you can check everything is fine by running.''

 bitbake -c kernel_configcheck -f virtual/kernel

''However this is automatically called by bitbake when rebuilding the kernel.''


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''NOTE''

In case you are courious...

Where do you find the .config file after having run '''bitbake -c menuconfig virtual/kernel''' ?

 tmp/work-shared/YOURKERNELNAME/kernel-build-artifacts