How to apply patches to a package in Buildroot?

Question

I am working on an embedded system that uses buildroot as a tool for building the kernel and the root filesystem. I want to apply some patches to this kernel source tree, Can somebody tell me how buildroot apply patches?

Answer 1

After studying the buildroot architecture, I came to know that buildroot uses quilt tool for applying the patches. quilt keeps track of all the patches in the a file named "series" which is present in the "patches" directory. You have to keep your patches in this directory. And add your entry of patches in the series file in the order in which you want the patches to be applied keeping the patch to be applied first at the top.

This way when you will run the buildroot makefile, it will automatically apply the patches listed in the series file.

Answer 2

To expand on @pradeepchhentri's answer. Quilt will look for a file located in the same folder as the *.mk file. To construct the appropriate file:

1. diff your source package from the original into a file called

   packagename-number-description.patch

   where

   packagename - has to be identical to the package name

   number - is the order in which the patches should be applied if you have more than one patch to apply (otherwise it will be applied alphabetically)

   description - can be any free text

2. Place this file into the package at the same level as the [packagename].mk file and the package/Config.in file.

Don't forget to blow away your build files or do a [package]-rebuild if you do this. You should see a "Patching..." message if this is done correctly.

Answer 3

BR2_GLOBAL_PATCH_DIR out-of-tree patches

Directory structure:

• .git/
• buildroot/ Buildroot submodule as mentioned at: https://stackoverflow.com/a/23635403/895245
• global_patch_dir/packagename/0001-my-test.patch

Add to config:

BR2_GLOBAL_PATCH_DIR=../global_patch_dir

Then build with:

cd buildroot
make

The patch should be applied to output/build/packagename-1.0.0/ before build.

Generate the patches with *_OVERRIDE_SRCDIR

If you just hack the packages directly under output/build/, you won't have anything to diff to.

Instead use the *_OVERRIDE_SRCDIR mechanism, which allows you to point to a git repo of your choice: How to modify the source of Buildroot packages for package development? , which you should then track as a git submodule.

Answer 4

some details about patch files in the buildroot project:

1. you have to

   diff -u "old_file" "new_file" > file.patch
   

while standing exactly above extracted location of your package tar.gz defined in

PACKAGE_NAME_SOURCE

it means, your path to the file must include extracted package folder name.

2. in case you wonder if the "old_file" path would be different from the original one - don't worry, the important one is the "new_file" path and name - it should match your package extracted one.

3. naming convention for the patches already used/defined in buildroot (all parts are separated with '-' sign):

   • 4 digits patch priority (starting from 0001)
   • target filename
   • reason for patching
   • .patch extention

example:

0001-configure.ac-convert-AC_TRY_COMPILE-AC_COMPILE_IFELS.patch

4. deposit patch file inside buildroot/package/"your package name"/ folder.

there is no need for configuration files to modify, all patches will be tried for application automatically.

5. in case of the failure, the reject-patch file (named similar to the file you are trying to patch but with .rej extention) will be deposited inside package extracted folder.