浅析Easy-ARMi.MAX283 GPIO中断驱动模块

首页 > 嵌入式开发 > Linux嵌入式作者：RainFly 2016年3月20日 21:46 星期日热度：9714° 字号：小中大评论：1

时间：2016-3-20 21:46 热度：9714° 评论：1 条

需要的是一步步解析这个代码中比较抽象难懂的点顺带举一反三共同学习不喜勿喷！

贴上源代码在光盘文件 ....\3.Linux\4.开发示例6、驱动示例GPIO中断

#inc lude<linux/init.h>

#include<linux/module.h>
#include<mach/gpio.h>
#include<asm/io.h>
#include"mach/../../mx28_pins.h"
#include <mach/pinctrl.h>
#include "mach/mx28.h"
#include<linux/fs.h>
#include <linux/io.h>
#include<asm/uaccess.h>
#include<linux/miscdevice.h>
#include<linux/irq.h>
#include<linux/sched.h>
#include<linux/interrupt.h>
#include<linux/timer.h>

#include <linux/kernel.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define GPIO_BUTTON_PIN PINID_SSP0_DATA4 //按键的引脚为P2.4

//具体引脚文件的配置在内核arch/arm/mach-mx28/mx28_pin.h文件中宏定义添加引脚配置

MXS_PING_ENCODE函数是通过计算得出引脚位置

#define MXS_PIN_ENCODE(b, p) \
((((b) & MXS_PIN_BANK_MAX) << MXS_PIN_BANK_BIT) |\
((p) & MXS_PIN_PINID_MAX))

static volatile int ev_press = 0;

static struct fasync_struct *button_async;

struct pin_desc_s{ //中断引脚描述结构体
unsigned int pin;
unsigned int irq;
unsigned int key_val;
};
static unsigned char key_val;
//初始化中断引脚结构体
struct pin_desc_s pin_desc = {
.pin = MXS_PIN_TO_GPIO(GPIO_BUTTON_PIN),
.key_val = 0,
};
static DECLARE_MUTEX(button_lock);
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

//中断处理函数
static irqreturn_t buttons_irq(int irq, void *dev_id)
{
struct pin_desc_s * pindesc = (struct pin_desc_s *)dev_id;
unsigned int pinval;

pinval = gpio_get_value(pindesc->pin);

if (pinval)
{
key_val = 1;
}
else
{
key_val = pindesc->key_val;
}
ev_press = 1;
wake_up_interruptible(&button_waitq); //唤醒等待队列里面的进程
kill_fasync (&button_async, SIGIO, POLL_IN); //异步通知
//printk("interrupt occur..........\n");
return IRQ_RETVAL(IRQ_HANDLED);
}

static int gpio_drv_open(struct inode *inode, struct file *file)
{
int iRet=0;

if (file->f_flags & O_NONBLOCK)
{
if (down_trylock(&button_lock))
return -EBUSY;
}
else
{
down(&button_lock);
}
gpio_direction_input(pin_desc.pin);
pin_desc.irq = gpio_to_irq(pin_desc.pin);
if (pin_desc.irq)
disable_irq(pin_desc.irq);
set_irq_type(pin_desc.irq, IRQF_TRIGGER_FALLING); //下降沿中断
//申请中断并设置中断处理函数
iRet = request_irq(pin_desc.irq, buttons_irq, IRQF_SHARED, "gpio_int", &pin_desc);
if (iRet != 0){
printk("request irq failed!! ret: %d irq:%d \n", iRet,pin_desc.irq);
return -EBUSY;
}
return 0;
}

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

if (file->f_flags & O_NONBLOCK)
{
if (!ev_press)
return -EAGAIN;
}
else
{
wait_event_interruptible(button_waitq, ev_press);
}
copy_to_user(buf, &key_val, 1);
ev_press = 0;

return 1;
}

int gpio_drv_close(struct inode *inode, struct file *file)
{
free_irq(pin_desc.irq, &pin_desc);
up(&button_lock);
return 0;
}

static int gpio_drv_fasync (int fd, struct file *filp, int on)
{
printk("driver: gpio_drv_fasync\n");
return fasync_helper (fd, filp, on, &button_async);
}

static struct file_operations gpio_drv_fops = {
.owner = THIS_MODULE,
.open = gpio_drv_open,
.read = gpio_drv_read,
.release = gpio_drv_close,
.fasync = gpio_drv_fasync,
};

static struct miscdevice button_miscdev =
{
.minor = MISC_DYNAMIC_MINOR,
.name = "magic-gpio",
.fops = &gpio_drv_fops,
};

static int __init gpio_drv_init(void)
{
int iRet=0;
printk("gpio_miscdev module init!\n");

iRet = misc_register(&button_miscdev);

// 注册miscdevice 混杂设备驱动公用主设备号为10，节省主设备号！

详细解释 http://blog.csdn.net/tong646591/article/details/8301925

if (iRet) {
printk("register failed!\n");
}
return 0;
}

static void __exit gpio_drv_exit(void)
{
printk("gpio_miscdev module exit!\n");
misc_deregister(&button_miscdev);
}

module_init(gpio_drv_init);
module_exit(gpio_drv_exit);

MODULE_AUTHOR("EasyARM283 By LZZ");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("gpio button interrupt module");