uClinux学习笔记之三.docxVIP

uClinux学习笔记之三??uClinux驱动开发初步?uClinux和linux的驱动开发是一致的,只是调试的方式不一样，学习uClinux的驱动开发也就是学习linux驱动开发的过程。linux驱动的调试需要至少一台电脑，外加像GDB，KDBG这样的源码级的内核调试工具，如果装一个虚拟机的话，那么只需要一台电脑即可了，但这样对电脑的性能有更高的要求。对于像uClinux的驱动调试，则最好是有开发板，也可以用模拟器。在ARM芯片上的移植是uClinux的一个重要应用。而最常用的仿真ARM的模拟器有国人开发的开源软件skyeye，不仅可以仿真ARM内核，并对以ARM作为内核的芯片作了进一步的支持。可以用skyeye -h 开查看skyeye能仿真的ARM芯片。当然，也可以对skyeye作一些扩展以满足自己的要求。以下是如何在uClinux添加驱动的过程。一、编写一个简单的字符驱动程序//---------------------------------------------mydevice.c-------------------------------------------#include linux/module.h#include linux/init.h#include linux/fs.h#include asm/uaccess.hMODULE_LICENSE(GPL);#define MAJOR_NUM 254 //主设备号#define DRIVER_NAME mydevicestatic ssize_tmydevice_read(struct file *, char *, size_t, loff_t*);static ssize_tmydevice_write(struct file *, const char *, size_t, loff_t*);//初始化字符设备驱动的file_operations结构体structfile_operationsmydevice_fops ={??????.read = mydevice_read,??????.write = mydevice_write,};static intglobal_var = 0; //mydevice设备的全局变量?int??mydevice_init(void){??????int ret;??????//注册设备驱动??????printk(0 mydevice_init /n);??????ret = register_chrdev(MAJOR_NUM,DRIVER_NAME,mydevice_fops);??????printk(0 register_chr_dev return %d /n,ret);??????if (ret 0)??????{???????????printk(0mydevice register failed /n);??????}??????else??????{???????????printk(0mydevice register success /n);??????}??????return ret;}void mydevice_exit(void){??????printk(0mydevice_exit!/n);??????unregister_chrdev(MAJOR_NUM,DRIVER_NAME);}static ssize_tmydevice_read(struct file *filp,char *buf,size_tlen,loff_t *off){??????//copy global_var from kernel space to user space??????if(copy_to_user(buf,global_var,sizeof(int)))??????{???????????return -EFAULT;??????}??????return sizeof(int);}static ssize_tmydevice_write(struct file *filp,const char *buf,size_tlen,loff_t *off){??????//copy data from user sapce to kernel space??????if(copy_from_user(global_var,buf,sizeof(int)))??????{???????????return -EFAULT;??????}??????return sizeof(int);}//----------------------------------------------