Writing a kernel callout

Updated: October 26, 2022

If your hardware platform isn't supported by the kernel callouts in the startup library, or by any of the available board-specific kernel callouts, you will need to write your own callout.

Before writing your own kernel callout, we recommend that you:


The source file you start from should have C prototypes for the routines as comments, so you'll know what parameters are being passed in.

If the new routines you write will be useful on multiple boards, you might want to keep the source file in your own copy of the startup library. If the routines will be useful for your board only, you can just copy your file to the directory where you keep your other board-specific files.

For information on the locations and names of the source files, see Kernel callout categories in this chapter.