简介
openembeded 有三个关键词:
bitbake: 可以想象成make
recipes: 是bitbake的入口文件，涉及到构建依赖 源码下载 配置 编译 build install 卸载等动作
layers: 在OpenEmbeded中，layer的概念是一个 recipes和相关配置文件的搜集整理集合,典型的分层主题是: kernel bsp board等。
最有用的layers是位于 build/conf/bblayers.conf 中
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk$ cat build/conf/bblayers.conf
# LAYER_CONF_VERSION is increased each time build/conf/bblayers.conf
# changes incompatibly
LCONF_VERSION = "7"
BBPATH = "${TOPDIR}"
BBFILES ?= ""
BBLAYERS ?= " \
/home/vimer/riscv_test/w500/freedom-u-sdk/openembedded-core/meta \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-oe \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-python \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-multimedia \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-filesystems \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-networking \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-gnome \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-xfce \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-riscv \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-clang \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-sifive \
/home/vimer/riscv_test/w500/freedom-u-sdk/meta-tensorflow-lite \
...
在上面的这些layers中，里面每一层的recipes文件，bitbake根据他们create task: fetch configure compile package.
上面的meta-*是每一个顶级layer,里面一般包含三种bitbake的元数据:
conf 目录
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk$ tree meta-sifive/conf/ -L 1
meta-sifive/conf/
├── layer.conf
└── machine
1 directory, 1 file
Recipes
./recipes-*/ (recipe files with .bb extension)
Good practices with Layers:
Only the maintainer of a layer is supposed to modify it Anyone willing to add or modify recipes need to create a separate layer that should be appended to the previous ones
bitbake是OpenEmbeded的基础构建，目前工作中需要对这个命令有一个基本的了解，所以这里 暂时记录一下，方便我们后面的使用。
bitbake
参考以下资料： https://www.kancloud.cn/digest/yocto/138624
初始化
一般的工程，都有一个初始化的脚本来enable bitbake的命令 以 freedom-u-sdk 为例，他的setup.sh为：
. ./meta-sifive/setup.sh
确定包的名字
命令: bitbake -s
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build$ bitbake -s | grep qemu
nativesdk-qemu :6.0.0-r0
nativesdk-qemu-helper :1.0-r9
nativesdk-qemuwrapper-cross :1.0-r0
qemu :6.0.0-r0
qemu-helper-native :1.0-r1
qemu-native :6.0.0-r0
qemu-system-native :6.0.0-r0
qemuwrapper-cross :1.0-r0
OE相关
bitbake-layers show-layers
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build$ bitbake-layers show-layers
NOTE: Starting bitbake server...
layer path priority
==========================================================================
meta /home/vimer/riscv_test/w500/freedom-u-sdk/openembedded-core/meta 5
meta-oe /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-oe 6
meta-python /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-python 7
meta-multimedia /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-multimedia 6
meta-filesystems /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-filesystems 6
meta-networking /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-networking 5
meta-gnome /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-gnome 7
meta-xfce /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-xfce 7
meta-riscv /home/vimer/riscv_test/w500/freedom-u-sdk/meta-riscv 6
meta-clang /home/vimer/riscv_test/w500/freedom-u-sdk/meta-clang 7
meta-sifive /home/vimer/riscv_test/w500/freedom-u-sdk/meta-sifive 8
meta-tensorflow-lite /home/vimer/riscv_test/w500/freedom-u-sdk/meta-tensorflow-lite 6
结合这里，我才意思到，OE的一点初步的设计思想，确实需要好好读一读spec。
create-layer
这里，bitbake-layers是利用了分层的思想，也就是后面你想对一个已经存在的工程进行修改，最好的方法是增加自己 的layers，去修改自己的东西，就比如上图中的数字就是这个层的执行顺序，可以暂时浅显的理解。下面新添加一个layers做下实验.
build$
bitbake-layers create-layer --priority 9 ../meta-test/mets-my-test-layer
NOTE: Starting bitbake server...
Add your new layer with 'bitbake-layers add-layer ../meta-test/mets-my-test-layer'
新的layers具有以下的文件清单:
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk$ tree meta-test/
meta-test/
└── mets-my-test-layer
├── conf
│ └── layer.conf
├── COPYING.MIT
├── README
└── recipes-example
└── example
└── example_0.1.bb
4 directories, 4 files
对于一个new layer, recommended actions are:
-
Update the REDEME
-
Update the priority in conf/layer.conf file
-
Apply your modifications and/or addons for the distrubtion.
但是这里有一个问题，就是使用针对原来 setup.sh不会把这个新的layer添加进入 show-layer命令，这个还有待考察如何做。
add-layers
上面已经新建了一个layer, 但是还没有添加进去，这里使用 bitbake-layer add-layer 命令添加。
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk$ cd meta-sifive/
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/meta-sifive$ bitbake-layers add-layer ../meta-test/mets-my-test-layer/
NOTE: Starting bitbake server...
Unable to find bblayers.conf
你看他最后报的错误，是找不到一个文件，那么，这个文件是在哪里呢？在build目录下:
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/meta-sifive$ cd ../build/
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build$ bitbake-layers add-layer ../meta-test/mets-my-test-layer/
NOTE: Starting bitbake server...
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build$ bitbake-layers show-layers
NOTE: Starting bitbake server...
layer path priority
==========================================================================
meta /home/vimer/riscv_test/w500/freedom-u-sdk/openembedded-core/meta 5
meta-oe /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-oe 6
meta-python /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-python 7
meta-multimedia /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-multimedia 6
meta-filesystems /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-filesystems 6
meta-networking /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-networking 5
meta-gnome /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-gnome 7
meta-xfce /home/vimer/riscv_test/w500/freedom-u-sdk/meta-openembedded/meta-xfce 7
meta-riscv /home/vimer/riscv_test/w500/freedom-u-sdk/meta-riscv 6
meta-clang /home/vimer/riscv_test/w500/freedom-u-sdk/meta-clang 7
meta-sifive /home/vimer/riscv_test/w500/freedom-u-sdk/meta-sifive 8
meta-tensorflow-lite /home/vimer/riscv_test/w500/freedom-u-sdk/meta-tensorflow-lite 6
mets-my-test-layer /home/vimer/riscv_test/w500/freedom-u-sdk/meta-test/mets-my-test-layer 9
看，这个时候就有咱们自己的新层了。
devtool
有了自己的layers, 这个时候就应该考虑如何往他里面添加app了。也就是添加recipes等文件
常用的命令是：
add 添加recipes
modify 提取源码
upgrade 更新recipes
serch 搜索package
可以参考这里: https://blog.csdn.net/qq_34160841/article/details/107287365
devtool add
- 首先在build目录中新建一个目录:
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build$ mkdir my_sources
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build/my_sources$ devtool add my-app my_app/
NOTE: Starting bitbake server...
NOTE: Starting bitbake server...
NOTE: Reconnecting to bitbake server...
NOTE: Retrying server connection (#1)...
NOTE: Reconnecting to bitbake server...
NOTE: Reconnecting to bitbake server...
NOTE: Retrying server connection (#1)...
NOTE: Retrying server connection (#1)...
NOTE: Starting bitbake server...
INFO: Using source tree as build directory since that would be the default for this recipe
INFO: Recipe /home/vimer/riscv_test/w500/freedom-u-sdk/build/workspace/recipes/my-app/my-app.bb has been automatically created; further editing may be required to make it fully functional
devtool 创建了一个名为 my-app的workspace, 用来存放 recipe 等文件的,在build目录下。
workspace的目录结构如下:
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build$ tree workspace/
workspace/
├── appends
│ └── my-app.bbappend
├── conf
│ └── layer.conf
├── README
└── recipes
└── my-app
└── my-app.bb
devtool build
vimer@user-HP:~/riscv_test/w500/freedom-u-sdk/build/my_sources$ devtool build my-app
NOTE: Starting bitbake server...
NOTE: Reconnecting to bitbake server...
NOTE: Retrying server connection (#1)...
Loading cache: 100% | | ETA: --:--:--
Loaded 0 entries from dependency cache.
Parsing recipes: 100% |###########################################################################| Time: 0:00:19
Parsing of 2658 .bb files complete (0 cached, 2658 parsed). 4031 targets, 186 skipped, 1 masked, 0 errors.
NOTE: Reconnecting to bitbake server...
NOTE: Previous bitbake instance shutting down?, waiting to retry...
NOTE: Retrying server connection (#1)...
Loading cache: 100% |#############################################################################| Time: 0:00:01
Loaded 4030 entries from dependency cache.
Parsing recipes: 100% |###########################################################################| Time: 0:00:00
Parsing of 2658 .bb files complete (2657 cached, 1 parsed). 4031 targets, 186 skipped, 1 masked, 0 errors.
NOTE: Resolving any missing task queue dependencies
Build Configuration:
BB_VERSION = "1.51.1"
BUILD_SYS = "x86_64-linux"
NATIVELSBSTRING = "universal"
TARGET_SYS = "riscv64-oe-linux"
MACHINE = "unmatched"
DISTRO = "nodistro"
DISTRO_VERSION = "2021.09.00"
TUNE_FEATURES = "riscv64 sifive-7-series"
meta
meta-oe
meta-python
meta-multimedia
meta-filesystems
meta-networking
meta-gnome
meta-xfce
meta-riscv
meta-clang
meta-sifive
meta-tensorflow-lite
mets-my-test-layer
workspace = "w500-dev:59cf33b17066bd50c8827b64cf18f70f18407e6e"
Initialising tasks: 100% |########################################################################| Time: 0:00:00
Sstate summary: Wanted 14 Local 0 Network 0 Missed 14 Current 63 (0% match, 81% complete)
Removing 10 stale sstate objects for arch riscv64: 100% |#########################################| Time: 0:00:00
NOTE: Executing Tasks
NOTE: my-app: compiling from external source tree /home/vimer/riscv_test/w500/freedom-u-sdk/build/my_sources/my_app
NOTE: Tasks Summary: Attempted 553 tasks of which 505 didn't need to be rerun and all succeeded.
NOTE: Writing buildhistory
NOTE: Writing buildhistory took: 1 seconds
NOTE: Build completion summary:
NOTE: do_populate_sysroot: 0.0% sstate reuse(0 setscene, 6 scratch)
NOTE: do_package: 0.0% sstate reuse(0 setscene, 5 scratch)
NOTE: do_packagedata: 0.0% sstate reuse(0 setscene, 5 scratch)
如果想更全面的认识bitbake：
https://blog.csdn.net/Archer1991/article/details/62423014