Creating and applying a git patch in a yocto build?

[#1]

Hey everyone! If you are looking for concise steps to create and apply a patch in a yocto build, this article will serve you well.

The reference taken in this article is of iMX93EVK yocto build. For this exercise, we are modifying a lpspi dts file in the BSP and creating a patch file but you may apply the same steps to other files in the BSP as well.

Step-1 Make changes to the dts file in your directory
example - arch/arm64/boot/dts/freescale/imx93-11x11-evk-lpspi.dts

Step-2 In your yocto build, go to the git folder 

cd imx-yocto-bsp-home/build_11x11/tmp/work/imx93_11x11_lpddr4x_evk-poky-linux/linux-imx/6.1.36+gitAUTOINC+04b05c5527-r0/git

Step-3 Execute 'git diff' to check the difference between your changes and the default ones 

Check the status by executing 'git status'

Step-4 Execute 'git add <file>'  , 'git commit -m <message>', and 'git format-patch -1'
to add a file and create a git format patch file for your changes.

 
copy the generated patch file to a location which yocto build look for the patches
Example- My yocto build looks for the patch in various locations, one of them is this one :-

sources/meta-imx/meta-bsp/recipes-kernel/linux/files,
so after creating the directory 'files', we can move the patch file to this folder

 Step-5 Edit the .bb file for linux recipes-kernel

for example - Open  /home/nxg06361/imx-yocto-bsp-home/sources/meta-imx/meta-bsp/recipes-kernel/linux/linux-imx_6.1.bb  for editing

Append the patch file name to the SRC_URI variable
 

 


You can also verify that your patch has been successfully applied or not by doing 'git log'

Voila ! that's all you need to do in order to create and apply a git patch for your yocto build.

[Blake001]

Thank you for the instructions. One question, since you changed the original dts, is it the best practice to do this? 

[Blake001]

The reason is the dts in tmp directory? If next time the yocto build the kernel, it will fectch the original source code and cover the change? 

I tried to copy the dts file to my new layer and changed it, but it looks like my method is wroing. Thanks again for your instructions.

[gaurav_sharma]

Hi @Blake001 the changes that I have done in the original dts, this practice is somewhat subjective. There will be times you would not want to maintain different copies of the dts for a small change. The other times you would want a different copy so it is not a hard-requirement.

[gaurav_sharma]

yes the dts source is fetched again the next time you trigger build and the changes get overridden. That's the reason we're making a patch in one of the instructions so that every time you trigger a build, this patch gets applied.