The BSP that encapsulates the hardware modifications for a given platform is mostly located in the bootloader, usually U-Boot (Das U-Boot) for ARM devices, and the Linux kernel. Both U-Boot and the Linux kernel have upstream development trees, at git.denx.de and http://kernel.org/ respectively, but it is very common for manufacturers of embedded hardware to provide their own trees for both bootloader and kernel.
Development in U-Boot and the Linux kernel is usually done externally to Yocto, as they are easy and quicker to build using a cross-compilation toolchain, like the one provided by Yocto's SDK.
The development work is then integrated into Yocto in one of two ways:
- With patches added to the kernel and U-Boot
bbappendfiles. This method will build the same source as the reference design board we are using as a base, and apply our changes over it. This is what we have seen in the previous recipe. - Using a different Git repository, forked from the Linux...