一、概述

Linux 内核编译流程如下：

1、配置 Linux 内核。

2、编译 Linux 内核。

说明：进入 Linux 内核源码，使用 make help 参看相关配置。

二、make menuconfig 工作原理

1、menuconfig 它本身是一个软件，只提供图形界面配置的一些逻辑，并不负责提供内容。

2、menuconfig 是内核源码树的各目录下的 kconfig 提供的。

3、menuconfig 中所有选中配置项的相关值会保存到配置文件中（默认配置文件为 .config）。

4、在编译内核时，Makefile 根据相关配置项选择需要编译的源码。

三、Kconfig 语法

参考文档：Documentation/kbuild/kconfig-language.txt。

Linux 驱动开发 六十五：《kconfig-language.txt》翻译_lqonlylove的博客-CSDN博客

四、Linux 内核中 Kconfig 分析

1、顶层 Kconfig 内容

#
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
#
mainmenu "Linux/$ARCH $KERNELVERSION Kernel Configuration"config SRCARCHstringoption env="SRCARCH"source "arch/$SRCARCH/Kconfig"

• mainmenu：标题栏；
• config：定义配置项；
  • string：数据类型；
  • env：导入 Kconfig 的环境变量；
• source：读取的配置文件位置。
  

2、arch/arm/Kconfig 内容

……
source "init/Kconfig" # 包含配置文件source "kernel/Kconfig.freezer"menu "System Type" # 定义配置菜单栏config MMU	# 在 System Type 下定义配置项bool "MMU-based Paged Memory Management Support"default yhelpSelect if you want MMU-based virtualised addressing spacesupport by paged memory management. If unsure, say 'Y'.#
# The "ARM system type" choice list is ordered alphabetically by option
# text.  Please add new entries in the option alphabetic order.
#
choiceprompt "ARM system type"default ARCH_VERSATILE if !MMUdefault ARCH_MULTIPLATFORM if MMUconfig ARCH_MULTIPLATFORMbool "Allow multiple platforms to be selected"depends on MMUselect ARCH_WANT_OPTIONAL_GPIOLIBselect ARM_HAS_SG_CHAINselect ARM_PATCH_PHYS_VIRTselect AUTO_ZRELADDRselect CLKSRC_OFselect COMMON_CLKselect GENERIC_CLOCKEVENTSselect MIGHT_HAVE_PCIselect MULTI_IRQ_HANDLERselect SPARSE_IRQselect USE_OF……config ARCH_VERSATILEbool "ARM Ltd. Versatile family"select ARCH_WANT_OPTIONAL_GPIOLIBselect ARM_AMBAselect ARM_TIMER_SP804select ARM_VICselect CLKDEV_LOOKUPselect GENERIC_CLOCKEVENTSselect HAVE_MACH_CLKDEVselect ICSTselect PLAT_VERSATILEselect PLAT_VERSATILE_CLOCKselect PLAT_VERSATILE_SCHED_CLOCKselect VERSATILE_FPGA_IRQhelpThis enables support for ARM Ltd Versatile board.……menu "Multiple platform selection"depends on ARCH_MULTIPLATFORM	# Multiple platform selection 依赖 ARCH_MULTIPLATFORM 配置项comment "CPU Core family selection"……#
# This is sorted alphabetically by mach-* pathname.  However, plat-*
# Kconfigs may be included either alphabetically (according to the
# plat- suffix) or along side the corresponding mach-* source.
#
source "arch/arm/mach-mvebu/Kconfig"
……menu "Bus support"
……
menu "Kernel Features"menu "CPU Power Management"source "drivers/cpufreq/Kconfig"source "drivers/cpuidle/Kconfig"endmenumenu "Floating point emulation"comment "At least one emulation must be selected"endmenu
……menu "Userspace binary formats"source "fs/Kconfig.binfmt"endmenumenu "Power management options"source "kernel/power/Kconfig"endmenusource "net/Kconfig"source "drivers/Kconfig"source "drivers/firmware/Kconfig"source "fs/Kconfig"source "arch/arm/Kconfig.debug"source "security/Kconfig"source "crypto/Kconfig"
if CRYPTO
source "arch/arm/crypto/Kconfig"
endifsource "lib/Kconfig"source "arch/arm/kvm/Kconfig"

• source：包含一个配置文件；
• menu：定义一个菜单项；
• choice：定义一个选项组；
• config：定义一个配置项；
• comment：定义一个注释；

3、其他配置文件

五、测试

1、添加菜单

为了方便测试，在顶层 Kconfig 下添加一个 bool 配置项，配置项内容如下：

menu "onlylove test"endmenu

2、添加 bool 类型配置

menu "onlylove test"config ONLYLOVE_TESTbool "onlylove test Management Support"endmenu

3、添加 tristate 类型配置

menu "onlylove test"config ONLYLOVE_TESTtristate "onlylove test Management Support"endmenu

4、添加 string 类型配置

menu "onlylove test"config ONLYLOVE_TESTstring "onlylove test Management Support"endmenu

5、添加 hex 类型配置

menu "onlylove test"config ONLYLOVE_TESThex "onlylove test Management Support"endmenu

6、添加 int 类型值

menu "onlylove test"config ONLYLOVE_TESTint "onlylove test Management Support"endmenu

7、查看配置是否生效

1、添加菜单和配置项

menu "onlylove test"config ONLYLOVE_TESTtristate "onlylove test Management Support"endmenu

2、查看旧配置文件

onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$ cat .config | grep ONLYLOVE_TEST
# CONFIG_ONLYLOVE_TEST is not set
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$

3、选中 onlylove test Management Support 配置项

4、查看新配置文件

onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$ cat .config | grep ONLYLOVE_TEST
CONFIG_ONLYLOVE_TEST=m
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$

六、向 Linux 内核中添加自己编写驱动

1、确定驱动所属类型

• ICM-20608 属于 SPI 设备。

2、找到对应Kconfig文件

onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$ pwd
/home/onlylove/my/linux/linux-imx-4.1.15/drivers/spi
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$ ls -l Kconfig 
-rw-rw-r-- 1 onlylove onlylove 20563 May 24  2019 Kconfig
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$

3、添加驱动文件

onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$ pwd
/home/onlylove/my/linux/linux-imx-4.1.15/drivers/spi
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$ ls -l spi-icm2068.c
ls: cannot access 'spi-icm2068.c': No such file or directory
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$  cp -f ~/my/imx6ull_drive/13_icm20608_spi/spi-icm2068.c ./
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$ ls -l spi-icm2068.c
-rw-rw-r-- 1 onlylove onlylove 12758 Nov 13 00:25 spi-icm2068.c
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15/drivers/spi$

4、添加配置项

config ONLYLOVE_ICM20608tristate "Icm20608 Device Support"helpThis supports user icm20608 device.

onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$ cat .config | grep ONLYLOVE_ICM20608
CONFIG_ONLYLOVE_ICM20608=y
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$

5、添加Makefile编译项

obj-$(CONFIG_ONLYLOVE_ICM20608)         += spi-icm2068.o

6、编译内核

onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$ make -j4
scripts/kconfig/conf  --silentoldconfig KconfigCHK     include/config/kernel.releaseCHK     include/generated/uapi/linux/version.hCHK     include/generated/utsrelease.h
make[1]: 'include/generated/mach-types.h' is up to date.CHK     include/generated/bounds.hCHK     include/generated/asm-offsets.hCALL    scripts/checksyscalls.shCHK     include/generated/compile.hCC      drivers/spi/spi-icm2068.oLD      drivers/spi/built-in.oLD      drivers/built-in.oLINK    vmlinuxLD      vmlinux.oMODPOST vmlinux.oGEN     .versionCHK     include/generated/compile.hUPD     include/generated/compile.hCC      init/version.oLD      init/built-in.oKSYM    .tmp_kallsyms1.oKSYM    .tmp_kallsyms2.oLD      vmlinuxSORTEX  vmlinuxSYSMAP  System.mapOBJCOPY arch/arm/boot/ImageBuilding modules, stage 2.MODPOST 27 modulesKernel: arch/arm/boot/Image is readyLZO     arch/arm/boot/compressed/piggy.lzoAS      arch/arm/boot/compressed/piggy.lzo.oLD      arch/arm/boot/compressed/vmlinuxOBJCOPY arch/arm/boot/zImageKernel: arch/arm/boot/zImage is ready
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$ 

日志 CC drivers/spi/spi-icm2068.o 表示 spi-icm2068 驱动编译成功。

7、驱动测试

1、Linux 启动日志

以上日志可以确定 icm20608 驱动加载成功。icm20608 设备 ID 读取成功。

2、app程序调用icm20608驱动

# ls
icm20608_app
# ls -l /dev/icm20608
crw-rw----    1 root     root       10,  62 Jan  1 00:00 /dev/icm20608
#
# ./icm20608_app /dev/icm20608
data[0] = 6 data[1] = 13 data[2] = 0 data[3] = 43 data[4] = 6 data[5] = 2067原始值:
gx = 6, gy = 13, gz = 0
ax = 43, ay = 6, az = 2067
temp = 1715
实际值:act gx = 0.37°/S, act gy = 0.79°/S, act gz = 0.00°/S
act ax = 0.02g, act ay = 0.00g, act az = 1.01g
act temp = 30.17°C
data[0] = 7 data[1] = 13 data[2] = 0 data[3] = 39 data[4] = 8 data[5] = 2063原始值:
gx = 7, gy = 13, gz = 0
ax = 39, ay = 8, az = 2063
temp = 1708
实际值:act gx = 0.43°/S, act gy = 0.79°/S, act gz = 0.00°/S
act ax = 0.02g, act ay = 0.00g, act az = 1.01g
act temp = 30.15°C
data[0] = 8 data[1] = 12 data[2] = -1 data[3] = 43 data[4] = 11 data[5] = 2067原始值:
gx = 8, gy = 12, gz = -1
ax = 43, ay = 11, az = 2067
temp = 1711
实际值:act gx = 0.49°/S, act gy = 0.73°/S, act gz = -0.06°/S
act ax = 0.02g, act ay = 0.01g, act az = 1.01g
act temp = 30.16°C
^C
#

数据读取成功。