字符设备驱动按键优化休眠

Posted 2021-01-22 zongzi10010

目录

• 字符设备驱动(五)按键优化
  • 按键值读取
  • 休眠读取
    • 程序设计
    • 测试

---

title: 字符设备驱动(五)按键优化
tags: linux
date: 2018-11-23 17:56:57
toc: true
---

字符设备驱动(五)按键优化

按键值读取

Linux内部有系统函数s3c2410_gpio_getpin能够读取GPIO的值

unsigned int s3c2410_gpio_getpin(unsigned int pin)
{
    void __iomem *base = S3C24XX_GPIO_BASE(pin);
    unsigned long offs = S3C2410_GPIO_OFFSET(pin);

    return __raw_readl(base + 0x04) & (1<< offs);
}

在中断处理函数中有个参数是dev_id,这个是由request_irq初始化的,处理函数可以用这个结构体传递参数

static irqreturn_t buttons_irq(int irq, void *dev_id) 

也就是说一个中断绑定了一个dev_id,可用作传递参数,卸载中断函数

request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
free_irq(IRQ_EINT0, &pins_desc[0]);

static irqreturn_t buttons_irq(int irq, void *dev_id)
{
    struct pin_desc * pindesc = (struct pin_desc *)dev_id;
    unsigned int pinval;
    
    pinval = s3c2410_gpio_getpin(pindesc->pin); //这里就读取到了
}

休眠读取

程序设计

程序设计目的:App去读取按键值,如果有按键中断触发(键值有改变)则打印,否则休眠.

read(key)
    if change 
        printf
    else
        sleep

也就是说App函数依然不变,但是需要修改驱动的读取函数,驱动的读取函数中有休眠的动作

// app.c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    int fd;
    unsigned char key_val;
    fd = open("/dev/xyz0", O_RDWR);
    if (fd < 0)
    {
        printf("can‘t open!
");
    }
    while (1)
    {
        read(fd, &key_val, 1);
        printf("key_val = 0x%x
", key_val);
    }
    return 0;
}

驱动程序中需要设计休眠,中断发生来唤醒首先定义一个等待队列,下述是一个宏

//生成一个等待队列头wait_queue_head_t,名字为name
DECLARE_WAIT_QUEUE_HEAD(name) 

// 定义一个名为`button_waitq`的队列
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

休眠函数如下,condition=0才休眠,定义在include/linux/wait.h

#define wait_event_interruptible(wq, condition)             ({                                      int __ret = 0;                              if (!(condition))                               __wait_event_interruptible(wq, condition, __ret);       __ret;                              })

唤醒也是一个宏,参数是等待队列,放置在中断函数处理中,定义在include/linux/wait.h

wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */

完整代码如下

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
//#include <linux/interrupt.h>

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;
volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;

static struct class *drv_class;
static struct class_device  *drv_class_dev;

// 定义一个名为`button_waitq`的队列
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
// flag=1 means irq happened and need to update
int flag=0;

struct pin_desc{
    unsigned int pin;
    unsigned int key_val;
};

/* 键值: 按下时, 0x01, 0x02, 0x03, 0x04 */
/* 键值: 松开时, 0x81, 0x82, 0x83, 0x84 */
static unsigned char key_val;

struct pin_desc pins_desc[4] = {
    {S3C2410_GPF0, 0x01},
    {S3C2410_GPF2, 0x02},
    {S3C2410_GPG3, 0x03},
    {S3C2410_GPG11, 0x04},
};

static irqreturn_t buttons_irq(int irq, void *dev_id)
{
    printk("irq%d
",irq);

    struct pin_desc * pindesc = (struct pin_desc *)dev_id;
    unsigned int pinval;
    
    pinval = s3c2410_gpio_getpin(pindesc->pin);

    if (pinval)
    {
        /* 松开 */
        key_val = 0x80 | pindesc->key_val;
    }
    else
    {
        /* 按下 */
        key_val = pindesc->key_val;
    }

    wake_up_interruptible(&button_waitq);   /* 唤醒休眠的进程 */
    flag=1;

    return IRQ_RETVAL(IRQ_HANDLED);
}

static int drv_open(struct inode *inode, struct file *file)
{
    /* 配置GPF0,2为输入引脚 */
    /* 配置GPG3,11为输入引脚 */
    request_irq(IRQ_EINT0,  buttons_irq, IRQT_BOTHEDGE, "S2", &pins_desc[0]);
    request_irq(IRQ_EINT2,  buttons_irq, IRQT_BOTHEDGE, "S3", &pins_desc[1]);
    request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "S4", &pins_desc[2]);
    request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "S5", &pins_desc[3]);   
    return 0;
}

int drv_close(struct inode *inode, struct file *file)
{
    free_irq(IRQ_EINT0, &pins_desc[0]);
    free_irq(IRQ_EINT2, &pins_desc[1]);
    free_irq(IRQ_EINT11,&pins_desc[2]);
    free_irq(IRQ_EINT19,&pins_desc[3]);
    return 0;
}


static ssize_t drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
    //int minor =  MINOR(file->f_dentry->d_inode->i_rdev);
    //printk("drv_write=%d
",minor);
    return 0;
}

static ssize_t drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
    if (size != 1)
    return -EINVAL;

    /* 如果没有按键动作, 休眠 */
    wait_event_interruptible(button_waitq, flag);

    /* 如果有按键动作, 返回键值 */
    copy_to_user(buf, &key_val, 1);
    flag = 0;
    
    return 1;
}


static struct file_operations drv_fops = {
    .owner  =   THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
    .open   =   drv_open,     
    .write  =   drv_write,
    .read   =   drv_read,    
    .release =  drv_close,  
};

static int major;
static int drv_init(void)
{
    int minor=0;
    major=register_chrdev(0, "drv", &drv_fops); // 注册, 告诉内核
    drv_class = class_create(THIS_MODULE, "drv");
    drv_class_dev = class_device_create(drv_class, NULL, MKDEV(major, 0), NULL, "xyz%d", minor);

    gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
    gpfdat = gpfcon + 1;
    gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
    gpgdat = gpgcon + 1;
    return 0;
}

static void drv_exit(void)
{
    unregister_chrdev(major, "drv"); // 卸载
    class_device_unregister(drv_class_dev);
    class_destroy(drv_class);
    iounmap(gpfcon);
    iounmap(gpgcon);
}

module_init(drv_init);
module_exit(drv_exit);
MODULE_AUTHOR("xxx");
MODULE_VERSION("0.1.0");
MODULE_DESCRIPTION("S3C2410/S3C2440 LED Driver");
MODULE_LICENSE("GPL");

测试

测试运行./text /dev/xyz0 & 后台运行

# ./test /dev/xyz0 &
# irq55
key_val = 0x3
irq55
key_val = 0x83
irq18
key_val = 0x2
irq18
key_val = 0x82
irq16
key_val = 0x1
irq16
key_val = 0x81
irq63
key_val = 0x4
irq63
key_val = 0x84

使用top查看占用

Load average: 0.00 0.01 0.00
  PID  PPID USER     STAT   VSZ %MEM %CPU COMMAND
  782   770 0        R     3096   5%   0% top
  770     1 0        S     3096   5%   0% -sh
  781   770 0        S     1312   2%   0% ./test /dev/xyz0

使用ps查看任务为S状态 休眠状态

# ps
  PID  Uid        VSZ Stat Command
    1 0          3092 S   init
  781 0          1312 S   ./test /dev/xyz0
  783 0          3096 R   ps