二 . 树莓派A20驱动程序编写(模板程序)

---

1 Makefile

Makefile文件编写如下：

ifeq ($(KERNELRELEASE),)
        KERNEL_DIR=/home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi
        PWD=$(shell pwd)
modules:
        $(MAKE) -C $(KERNEL_DIR) M=$(PWD) modules
        arm-linux-gnueabihf-gcc -o test test.c
modules_install:
        $(MAKE) -C $(KERNEL_DIR) M=$(PWD) modules_install
clean:
        rm -rf *.ko *.o .tmp_versions *.mod.c modules.order Module.symvers .*.cmd
else
        obj-m:=test.o
endif

2 *.c文件

建立一个test.文件，编写内容如下：

#include "linux/init.h"
#include <linux/kernel.h>
#include <linux/module.h>

static int __init empty_init(void)
{
        printk("---driver init---\r\n");
        return 0;
}

static void __exit empty_exit(void)
{
        printk("---dirver exit---\r\n");
}

module_init(empty_init);
module_exit(empty_exit);

MODULE_DESCRIPTION("Driver for empty");
MODULE_AUTHOR("wit_yuan");
MODULE_LICENSE("GPL");

3 获取ko文件

3.1 编译程序

wityuan@ubuntu:~/Desktop/A20_driver$ make
make -C /home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi M=/home/wityuan/Desktop/A20_driver modules
make[1]: Entering directory `/home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi'

  ERROR: Kernel configuration is invalid.
         include/generated/autoconf.h or include/config/auto.conf are missing.
         Run 'make oldconfig && make prepare' on kernel src to fix it.


  WARNING: Symbol version dump /home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi/Module.symvers
           is missing; modules will have no dependencies and modversions.

  Building modules, stage 2.
/home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi/scripts/Makefile.modpost:42: include/config/auto.conf: No such file or directory
make[2]: *** No rule to make target `include/config/auto.conf'.  Stop.
make[1]: *** [modules] Error 2
make[1]: Leaving directory `/home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi'
make: *** [modules] Error 2

这个问题主要原因在编译驱动的时候，认为内核没有编译。所以是编译环境导致。
在marsboard sdk路径下，进入linux-sunxi目录下，做这样的操作：

$ cd linux-sunxi
$ cp marsboard_kernel_defconfig arch/arm/configs/
$ vi Makefile
...
#ARCH           ?= $(SUBARCH)
ARCH            = arm
#CROSS_COMPILE  ?= $(CONFIG_CROSS_COMPILE:"%"=%)
CROSS_COMPILE  = arm-linux-gnueabihf-

$ make marsboard_kernel_defconfig
$ make uImage

之后，在编写的驱动路径下，执行

$ make
...
make -C /home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi M=/home/wityuan/Desktop/A20_driver modules
make[1]: Entering directory `/home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi'
  CC [M]  /home/wityuan/Desktop/A20_driver/test.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/wityuan/Desktop/A20_driver/test.mod.o
  LD [M]  /home/wityuan/Desktop/A20_driver/test.ko
make[1]: Leaving directory `/home/wityuan/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi'
arm-linux-gnueabihf-gcc -o test test.c
test.c:2:24: fatal error: linux/init.h: No such file or directory
compilation terminated.
make: *** [modules] Error 1

从上图看，已经报错了，但是，其实还是能生成.ko文件的，如下图所示：

wityuan@ubuntu:~/Desktop/A20_driver$ ls
Makefile  modules.order  Module.symvers  test.c  test.ko  test.mod.c  test.mod.o  test.o
wityuan@ubuntu:~/Desktop/A20_driver$ 

我们在后面将驱动做的差不多的时候，再回过头来解决这个问题。

3.2 安装驱动程序

将上面生成的test.ko通过tftp下载到开发板上，然后再开发板上进行安装，如下所示：

root@marsboard:~# 
root@marsboard:~# insmod test.ko 
---driver init---
root@marsboard:~# rmmod test 
---dirver exit---
root@marsboard:~# 

到这个步骤为止，就可以判定我们的驱动程序编写成功了。

4 问题解决

4.1 linux/init.h不能找到

该篇留下了一个问题，也就是不能找到linux/init.h文件，其实搜寻文件，还是能找到该文件的：

wityuan@ubuntu:~/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi$ find -name "init.h"
./include/linux/init.h
./include/config/mmc/paranoid/sd/init.h
./include/config/debug/memory/init.h
./arch/x86/include/asm/init.h
./arch/avr32/mach-at32ap/include/mach/init.h
./arch/mips/powertv/init.h
./arch/um/include/shared/init.h
./drivers/video/sis/init.h
./drivers/staging/keucr/init.h
./drivers/net/wireless/wl12xx/init.h
./drivers/net/wireless/wl1251/init.h
wityuan@ubuntu:~/Downloads/MarsBoard-A20-Linux-SDK-V1.2/linux-sunxi$ 

d第一个文件便是，解决方法，待定。。。