六、【ioctl】应用程序和驱动程序中的ioctl

1、接口函数介绍

很多设备除了读和写之外，还需要驱动提供其它操作能力，例如：获取LCD尺寸、修改串口波特率

（应用层）函数原型：

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1 2	#include <sys/ioctl.h>  int ioctl(int fd, unsigned long request, ...);

（driver）提供接口函数

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struct file_operations {     .....     long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);     long (*compat_ioctl) (struct file *, unsigned int, unsigned long);     ......     }

2.6.36之后的内核版本只支持unlocked_ioctl，之前的一些过渡版本两者都支持，更早的版本只支持compat_ioctl

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1	long (*unlocked_ioctl) (struct file * filp, unsigned int cmd , unsigned long arg);

参数：

• filp：指向打开的文件信息结构体。
• cmd：驱动提供给应用程序的命令字。
• arg：应用程序与驱动之间传递的参数。

2、命令字的组成

（1）bit解释

• bit[31:30]：参数传递的方向。应用--->驱动、驱动--->应用、应用<--->驱动、不需要参数.
• bit[29:16]：参数的大小，用数据类型表示大小char int struct xxx。
• bit[15:8]：魔数/幻数，用于区分不同驱动的命令字，一般设置为某个字符的ASCII码。
• bit[7:0]：命令字的序号。

（2）内核中提供的生成命令字的宏

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#define _IO(type,nr)        _IOC(_IOC_NONE,(type),(nr),0) #define _IOR(type,nr,size)  _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size))) #define _IOW(type,nr,size)  _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size))) #define _IOWR(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size))) _IO---生成没有参数传递的命令字。 _IOR--生成应用从驱动获取参数的命令字。 _IOW--生成应用给驱动传递参数的命令字。 _IOWR--生成双向传参的命令字。

参数：

• type：魔数/幻数，用于区分不同驱动的命令字，一般设置为某个字符的ASCII码
• nr：命令字的序号
• size：参数的大小，用数据类型表示大小char int struct xxx

例如：　

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#define BEEP_ON _IO('B',0) #define BEEP_OFF _IO('B',1)   #define LED_ON _IOW('L',0,unsigned int) #define LED_OFF _IOW('L',1,unsigned int)

3、例程（实现beep）

beep_drv.c

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#include <linux/init.h> #include <linux/module.h> #include <linux/kernel.h> #include <linux/cdev.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/ioport.h> #include <linux/io.h> #include <linux/uaccess.h>  #include <linux/types.h> #include <linux/ioctl.h> static struct cdev beep; static dev_t dev; static struct class *beep_cls=NULL; static struct device * beep_dev=NULL; static struct resource *beep_res  = NULL; static void __iomem *GPIOCBASE = NULL; static void __iomem *GPIOCOUT = NULL; static void __iomem *GPIOCOUTENB= NULL; static void __iomem *GPIOCALTFN0 = NULL; static void __iomem *GPIOCALTFN1 = NULL;   #define BEEP_ON  _IO('B',0) #define BEEP_OFF   _IO('B',1)   static  int beep_open(struct inode* inode,struct file *filp) {     printk(KERN_INFO"beep_open\n");     return 0; }   static  int beep_close(struct inode* inode,struct file *filp) {     printk(KERN_INFO"beep_close\n");     return 0; }   static ssize_t beep_write(struct file *filp, const char __user *user, size_t  size, loff_t *oft) {       printk(KERN_INFO"beep_write\n");      return size; }   static long beep_ioctl (struct file *filp, unsigned int cmd, unsigned long  arg) {       switch(cmd)       {             case BEEP_ON:                 writel(readl(GPIOCOUT)|((0x01<<14)),GPIOCOUT);                 break;         case BEEP_OFF:                 writel(readl(GPIOCOUT)&(~(0x01<<14)),GPIOCOUT);         default:             return -ENOIOCTLCMD;                  }      return 0; } struct file_operations fops= {     .open = beep_open,     .release = beep_close,     .write = beep_write,     .unlocked_ioctl = beep_ioctl, };   static int __init  beep_init(void) {       int ret;        printk(KERN_INFO"beep_init\n");     ret = alloc_chrdev_region(&dev, 0, 1,"beep_chrdev");     if(ret!=0)     {         printk(KERN_INFO"register char dev failed\n");         goto alloc_chrdev_region_err;     }     beep.owner = THIS_MODULE;     cdev_init(&beep,&fops);     ret=cdev_add(&beep, dev, 1);     if(ret!=0)     {         printk(KERN_INFO"add char device failed\n");         goto cdev_add_err;     }     beep_cls = class_create(THIS_MODULE, "beep_class");     if(IS_ERR(beep_cls))     {         printk(KERN_INFO"class create failed\n");         ret = -EBUSY;         goto class_create_err;     }     beep_dev= device_create(beep_cls, NULL,dev, NULL, "beep_dev");     if(IS_ERR(beep_dev))     {         printk(KERN_INFO"device create failed\n");         ret = -ENOMEM;         goto device_create_err;     }     beep_res = request_mem_region(0xc001c000,0x68,"beep_iomem");     if(beep_res==NULL)     {         printk(KERN_INFO"request memory region failed\n");         ret = -EBUSY;         goto request_mem_region_err;     }     GPIOCBASE = ioremap(0xc001c000,0x68);     if(GPIOCBASE==NULL)     {         printk(KERN_INFO"ioremap failed");         ret = -EBUSY;         goto ioremap_err;     }     GPIOCOUT = GPIOCBASE+0x00;     GPIOCOUTENB = GPIOCBASE+0x04;     GPIOCALTFN0 = GPIOCBASE+0x20;     GPIOCALTFN1 = GPIOCBASE+0x24;     //beep     writel(readl(GPIOCOUTENB)|(0x01<<14),GPIOCOUTENB);     writel(readl(GPIOCALTFN0) &(~(0x03<<28)),GPIOCALTFN0);     writel(readl(GPIOCALTFN0) |(1<<28),GPIOCALTFN0);     writel(readl(GPIOCOUT)&(~(0x01<<14)),GPIOCOUT);         return 0; ioremap_err:        release_mem_region(0xc001c000,0x68); request_mem_region_err:     device_destroy(beep_cls , dev); device_create_err:     class_destroy(beep_cls); class_create_err:     cdev_del(&beep); cdev_add_err:     unregister_chrdev_region(dev,1); alloc_chrdev_region_err:         return 0; }   static void __exit beep_exit(void) {     printk(KERN_INFO"xxxx__exit\n");        //取锟斤拷映锟斤拷     iounmap(GPIOCBASE);     //锟酵凤拷IO锟节达拷     release_mem_region(0xc001c000,0x68);     device_destroy(beep_cls , dev);     class_destroy(beep_cls);     cdev_del(&beep);     unregister_chrdev_region(dev, 1); } module_init(beep_init); module_exit(beep_exit); MODULE_AUTHOR("yqf"); MODULE_DESCRIPTION("beep driver program"); MODULE_LICENSE("GPL");

main.c

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#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <sys/ioctl.h>   #define BEEP_ON _IO('B',0) #define BEEP_OFF _IO('B',1)   int main() {     int fd;     char buff[2]={0};     fd = open("/dev/beep_dev",O_RDWR);     if(fd<0)     {         perror("open bepp dev error!");            }     while(1)     {         ioctl(fd,BEEP_ON);         sleep(1);         ioctl(fd,BEEP_OFF);          sleep(1);     }            close(fd); }