| | 1 | // -*- mode:doc; -*- |
| | 2 | // vim: set syntax=asciidoc: |
| | 3 | |
| | 4 | == How Buildroot works |
| | 5 | |
| | 6 | As mentioned above, Buildroot is basically a set of Makefiles that |
| | 7 | download, configure, and compile software with the correct options. It |
| | 8 | also includes patches for various software packages - mainly the ones |
| | 9 | involved in the cross-compilation toolchain (+gcc+, +binutils+ and |
| | 10 | +uClibc+). |
| | 11 | |
| | 12 | There is basically one Makefile per software package, and they are |
| | 13 | named with the +.mk+ extension. Makefiles are split into many different |
| | 14 | parts. |
| | 15 | |
| | 16 | * The +toolchain/+ directory contains the Makefiles |
| | 17 | and associated files for all software related to the |
| | 18 | cross-compilation toolchain: +binutils+, +gcc+, +gdb+, |
| | 19 | +kernel-headers+ and +uClibc+. |
| | 20 | |
| | 21 | * The +arch/+ directory contains the definitions for all the processor |
| | 22 | architectures that are supported by Buildroot. |
| | 23 | |
| | 24 | * The +package/+ directory contains the Makefiles and |
| | 25 | associated files for all user-space tools and libraries that Buildroot |
| | 26 | can compile and add to the target root filesystem. There is one |
| | 27 | sub-directory per package. |
| | 28 | |
| | 29 | * The +linux/+ directory contains the Makefiles and associated files for |
| | 30 | the Linux kernel. |
| | 31 | |
| | 32 | * The +boot/+ directory contains the Makefiles and associated files for |
| | 33 | the bootloaders supported by Buildroot. |
| | 34 | |
| | 35 | * The +system/+ directory contains support for system integration, e.g. |
| | 36 | the target filesystem skeleton and the selection of an init system. |
| | 37 | |
| | 38 | * The +fs/+ directory contains the Makefiles and |
| | 39 | associated files for software related to the generation of the |
| | 40 | target root filesystem image. |
| | 41 | |
| | 42 | Each directory contains at least 2 files: |
| | 43 | |
| | 44 | * +something.mk+ is the Makefile that downloads, configures, |
| | 45 | compiles and installs the package +something+. |
| | 46 | |
| | 47 | * +Config.in+ is a part of the configuration tool |
| | 48 | description file. It describes the options related to the |
| | 49 | package. |
| | 50 | |
| | 51 | The main Makefile performs the following steps (once the |
| | 52 | configuration is done): |
| | 53 | |
| | 54 | * Create all the output directories: +staging+, +target+, +build+, |
| | 55 | etc. in the output directory (+output/+ by default, |
| | 56 | another value can be specified using +O=+) |
| | 57 | |
| | 58 | * Generate the toolchain target. When an internal toolchain is used, this |
| | 59 | means generating the cross-compilation toolchain. When an external |
| | 60 | toolchain is used, this means checking the features of the external |
| | 61 | toolchain and importing it into the Buildroot environment. |
| | 62 | |
| | 63 | * Generate all the targets listed in the +TARGETS+ variable. This |
| | 64 | variable is filled by all the individual components' |
| | 65 | Makefiles. Generating these targets will trigger the compilation of |
| | 66 | the userspace packages (libraries, programs), the kernel, the |
| | 67 | bootloader and the generation of the root filesystem images, |
| | 68 | depending on the configuration. |
| | 69 | |
projects / buildroot-mgba.git / blame_incremental