imx6 yocto编译备忘
1、git把源码下到fsl-release-bsp后，配置编译选项：
$DISTRO=fsl-imx-fb MACHINE=imx6qsabresd source fsl-setup-release.sh -b build-fb
-b 可以指定你要将文件编译到哪个目录
2、全编译：
在build-fb目录下执行：
$bitbake core-image-base
编译出来的image在 fsl-releases-bsp/build-fb/tmp/deploy/images/imx6qsabresd目录下，包括的u-boot zImage rootfs。如不小心删掉了deploy/images/imx6qsabresd下的文件，想重新生成，执行如下步骤：
$bitbake -c cleanall core-image-base
$bitbake -c compile -f u-boot-imx
$bitbake -c deploy -f u-boot-imx //部署生成的u-boot镜像到deploy/images/imx6qsabresd
$bitbake -c compile -f linux-imx
$bitbake -c deploy -f linux-imx //部署生成的内核镜像到deploy/images/imx6qsabresd
$bitbake core-image-base //生成rootfs到deploy/images/imx6qsabresd
如有报错：
1）ERROR: Task 4 (.../fsl-release-bsp/sources/meta-fsl-bsp-release/imx/meta-bsp/recipes-bsp/u-boot/u-boot-imx_2015.04.bb, do_compile) failed with exit code '1'
是因执行完第一步配置，把local.conf覆盖了，须再把uboot重新配置：
$echo "UBOOT_CONFIG = \"emmc\"" >> conf/local.conf
2）执行compile -f linux-imx报错：
.../fsl-release-bsp/build-fb/tmp/work-shared/imx6qsabresd/kernel-source is not clean, please run 'make mrproper'
则按提示的路径直接cd到kernel-source，执行make mrproper即可。
3、U-Boot配置：
$cd build-fb
$echo "UBOOT_CONFIG = \"emmc\"" >> conf/local.conf
$MACHINE=imx6qsabresd bitbake -c deploy u-boot-imx
4、生成toolchain：
$cd build-fb
$bitbake meta-toolchain
5、安装toolchain：
$cd tmp/deploy/sdk
$./fsl-imx-fb-glibc-i686-meta-toolchain-cortexa9hf-vfp-neon-toolchain-4.1.15-1.2.0.sh
Freescale i.MX Release Distro SDK installer version 4.1.15-1.2.0
================================================================
Enter target directory for SDK (default: /opt/fsl-imx-fb/4.1.15-1.2.0): （回车，选择默认安装路径）
The directory "/opt/fsl-imx-fb/4.1.15-1.2.0" already contains a SDK for this architecture.
If you continue, existing files will be overwritten! Proceed[y/N]? y
[sudo] password for test01:
Extracting SDK.................done
Setting it up...done
SDK has been successfully set up and is ready to be used.
Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
$ . /opt/fsl-imx-fb/4.1.15-1.2.0/environment-setup-cortexa9hf-vfp-neon-poky-linux-gnueabi
6、安装完成后根据提示配置环境变量：
$. /opt/fsl-imx-fb/4.1.15-1.2.0/environment-setup-cortexa9hf-vfp-neon-poky-linux-gnueabi
然后就可在源码文件夹独立编译：
1）uboot源码：fsl-releases-bsp/build-fb/tmp/work/imx6qsabresd-poky-linux-gnueabi/u-boot-imx/2015.04-r0/git
$make mx6qsabresd_defconfig
$make
2）kernel源码：fsl-releases-bsp/build-fb/tmp/work/imx6qsabresd-poky-linux-gnueabi/linux-imx/4.1.15-r0/git
imx6q的默认配置defconfig文件在：
fsl-release-bsp\sources\meta-fsl-arm\recipes-kernel\linux\linux-fslc-mx6
可将其拷贝到内核文件夹，在menuconfig中将其load后save到.config中(load前一定要先执行toolchain的环境变量导入，否则会加载失败)，再编译：
$export ARCH=arm
$make zImage
*另：完成第6步后，可单独编译测试用的*.c代码：
$echo $CC
arm-poky-linux-gnueabi-gcc -march=armv7-a -mfloat-abi=hard -mfpu=neon -mtune=cortex-a9 --sysroot=/opt/fsl-imx-fb/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-poky-linux-gnueabi
可见CC中已配好相关的编译选项，所以用以下命令编译写的测试hello.c：
$ $CC -o hello hello.c
生成的二进制文件属性：
$file hello
hello: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 2.6.32, BuildID[sha1]=b5885ce459ae1de3413051cdeb8e912d5f510f9a, not stripped
对于Makefile的toolchain配置：
CROSS_COMPILE = /opt/fsl-imx-fb/4.1.15-1.2.0/sysroots/i686-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-
CXX = $(CROSS_COMPILE)g++ -mfloat-abi=hard -mfpu=neon --sysroot=/opt/fsl-imx-fb/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-poky-linux-gnueabi
CC = $(CROSS_COMPILE)gcc -mfloat-abi=hard -mfpu=neon --sysroot=/opt/fsl-imx-fb/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-poky-linux-gnueabi
LINK = $(CROSS_COMPILE)g++ -mfloat-abi=hard -mfpu=neon --sysroot=/opt/fsl-imx-fb/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-poky-linux-gnueabi
其中最为核心的是sysroot这个选项，这个选项将告诉toolchian去哪里查找库与头文件，而如果不指定这个，那么就会出现问题。