yocto的hello world

痛定思痛。 2022-08-28 14:50 362阅读 0赞

为了辅助理解yocto编译的架构和编译过程，写一遍helloworld会好很多。

首先下载编译poky

$ git clone git://git.yoctoproject.org/poky
    $ cd poky
    $ source oe-init-build-env
    $ bitbake core-image-sato

创建自己的layer：meta-mylayer

$ bitbake-layers create-layer meta-mylayer
    NOTE: Starting bitbake server...
    Add your new layer with 'bitbake-layers add-layer meta-mylayer'

在poky目录下通过bitbake-layers增加meta-layer，提示找不到bblayers.conf，原来是要在build目录下添加才对：

hui@hui:~/disk4t/codes/poky
    $ bitbake-layers add-layer meta-mylayer
    NOTE: Starting bitbake server...
    Unable to find bblayers.conf

在build目录下add-layer, 没有指定meta-mylayer路径报错

hui@hui:~/disk4t/codes/poky/build
    $ bitbake-layers add-layer meta-mylayer
    NOTE: Starting bitbake server...
    Specified layer directory /home/hui/disk4t/codes/poky/build/meta-mylayer doesn't exist

指定路径后可以了：

$ bitbake-layers add-layer ../meta-mylayer
    NOTE: Starting bitbake server...

cat bblayer.conf可以看到meta-mylayer加到了最后一行

$ cat conf/bblayers.conf 
    # POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf
    # changes incompatibly
    POKY_BBLAYERS_CONF_VERSION = "2"
    
    BBPATH = "${TOPDIR}"
    BBFILES ?= ""
    
    BBLAYERS ?= " \
      /home/hui/disk4t/codes/poky/meta \
      /home/hui/disk4t/codes/poky/meta-poky \
      /home/hui/disk4t/codes/poky/meta-yocto-bsp \
      /home/hui/disk4t/codes/poky/meta-mylayer \
      "

查看meta-mylayer目录

$ tree .
    .
    ├── conf
    │   └── layer.conf
    ├── COPYING.MIT
    ├── README
    └── recipes-example
        └── example
            └── example_0.1.bb

新建files目录，在files目录下添加hello.c文件

$ tree meta-mylayer/
    meta-mylayer/
    ├── conf
    │   └── layer.conf
    ├── COPYING.MIT
    ├── README
    └── recipes-example
        └── example
            ├── example_0.1.bb
            └── files
                └── hello.c

修改example\_0.1.bb，定义编译规则

SUMMARY = "bitbake-layers recipe"
    LICENSE = "MIT"
    
    python do_display_banner() {
        bb.plain("***********************************************");
        bb.plain("*                                             *");
        bb.plain("*  Example recipe created by bitbake-layers   *");
        bb.plain("*                                             *");
        bb.plain("***********************************************");
    }
    
    DESCRIPTION = "Simple helloworld application"
    LICENSE = "MIT"
    LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
    
    SRC_URI = "file://hello.c"
    
    S = "${WORKDIR}"
    
    do_compile() {
            ${CC} hello.c ${LDFLAGS} -o helloworld
    }
    
    do_install() {
            install -d ${D}${bindir}
            install -m 0755 helloworld ${D}${bindir}
    }

编译

$ bitbake example
    Loading cache: 100% |########################################################################################################################################################################| Time: 0:00:00
    Loaded 1470 entries from dependency cache.
    NOTE: Resolving any missing task queue dependencies
    
    Build Configuration:
    BB_VERSION           = "1.51.1"
    BUILD_SYS            = "x86_64-linux"
    NATIVELSBSTRING      = "universal"
    TARGET_SYS           = "x86_64-poky-linux"
    MACHINE              = "qemux86-64"
    DISTRO               = "poky"
    DISTRO_VERSION       = "3.3+snapshot-bf47addb34debc049b59e5e466228f00045c2061"
    TUNE_FEATURES        = "m64 core2"
    TARGET_FPU           = ""
    meta                 
    meta-poky            
    meta-yocto-bsp       
    meta-mylayer         = "master:bf47addb34debc049b59e5e466228f00045c2061"
    
    Initialising tasks: 100% |###################################################################################################################################################################| Time: 0:00:00
    Sstate summary: Wanted 0 Local 0 Network 0 Missed 0 Current 153 (0% match, 100% complete)
    NOTE: Executing Tasks
    NOTE: Tasks Summary: Attempted 623 tasks of which 623 didn't need to be rerun and all succeeded.

然后在tmp目录下find生成的Helloworld

$ find . -name "helloworld"
    ./work-shared/gcc-11.2.0-r0/gcc-11.2.0/libgo/misc/cgo/fortran/helloworld
    ./work/core2-64-poky-linux/gstreamer1.0/1.18.4-r0/gstreamer-1.18.4/tests/examples/helloworld
    ./work/core2-64-poky-linux/example/0.1-r0/packages-split/example/usr/bin/helloworld
    ./work/core2-64-poky-linux/example/0.1-r0/packages-split/example-dbg/usr/bin/.debug/helloworld
    ./work/core2-64-poky-linux/example/0.1-r0/package/usr/bin/.debug/helloworld
    ./work/core2-64-poky-linux/example/0.1-r0/package/usr/bin/helloworld
    ./work/core2-64-poky-linux/example/0.1-r0/image/usr/bin/helloworld
    ./work/core2-64-poky-linux/example/0.1-r0/helloworld

在conf/local.conf文件中增加IMAGE\_INSTALL

IMAGE_INSTALL = "example"

`IMAGE_INSTALL_append = "example"`,用IMAGE\_INSTALL\_append如下会报错，没有研究应该怎么用

$ bitbake core-image-sato
    ERROR: Variable IMAGE_INSTALL_append contains an operation using the old override syntax. Please convert this layer/metadata before attempting to use with a newer bitbake.

然后build core-image-sato

$ bitbake core-image-sato

编译完成后再次运行，这次可能因为加了helloworld的缘故，没有进入到图形界面，但是在QEMU的shell环境中就可以运行helloworld程序，输出’Hello World!’。

$ runqemu tmp/deploy/images/qemux86-64/bzImage-qemux86-64.bin tmp/deploy/images/qemux86-64/core-image-sato-qemux86-64.ext4

参考：

*  [Yocto项目介绍及入门 – 嵌入师工程师必备利器][Yocto_ _]
 *  [DART-6UL - Hello, World!][DART-6UL - Hello_ World]

[Yocto_ _]: https://www.cnblogs.com/chegxy/p/14394333.html#3-%E5%A6%82%E4%BD%95%E5%BF%AB%E9%80%9F%E4%B8%8A%E6%89%8Byocto%E9%A1%B9%E7%9B%AE
[DART-6UL - Hello_ World]: https://variwiki.com/index.php?title=Yocto_Hello_World