编写mipsel mt7620 Led驱动（四，内核互斥锁）

原文地址：http://www.cnblogs.com/xuyh/p/3899938.html

为什么需要内核互斥锁?

多核处理器下，会存在多个进程处于内核态的情况，而在内核态下，进程是可以访问所有内核数据的，因此要对共享数据进行保护，即互斥处理

 

 

互斥锁主要函数:

//创建互斥锁

DEFINE_MUTEX(mutexname);

或者struct  mutex mutexname；mutex_init(&mutexname);

//加锁,如果加锁不成功，会阻塞当前进程

void mutex_lock(struct mutex *lock);

//解锁

void mutex_unlock(struct mutex *lock);

//尝试加锁，会立即返回，不会阻塞进程

int mutex_trylock(struct mutex *lock);

 

 

#ifndef __RALINK_GPIO_H__ 
#define __RALINK_GPIO_H__

#include  
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#include

#include  
//The Kenel header file, include soc virtual address 
#include

#define RALINK_SYSCTL_ADDR        RALINK_SYSCTL_BASE    // system control 
#define RALINK_REG_GPIOMODE        (RALINK_SYSCTL_ADDR + 0x60) //GPIO MODE

#define RALINK_PRGIO_ADDR        RALINK_PIO_BASE // Programmable I/O

#define  RALINK_REG_PIO7140DATA  (RALINK_PRGIO_ADDR + 0x70)    //数据地址

#define  RALINK_REG_PIO7140DIR     (RALINK_PRGIO_ADDR + 0x74)    //方向地址

typedef  enum  led_stat//ioctl控制cmd 
{ 
    SET_LED_ON = 1, 
    SET_LEN_OF, 
    SET_LED_DIR 
}SET_LED_CMD;

#endif

 

 

#include "gpio.h"

#define LED_DRIVER_NAME "led_driver" //设备名字

//创建互斥锁 
static DEFINE_MUTEX(led_mutex);

/** 
* 设置gpio40-gpio71模式为gpio. 
*RGMII2_GPIO_MODE 对应寄存器第10位 
*/ 
static void set_7140_gpio_mode(void) 
{ 
    u32 gpiomode; 
    
    gpiomode = le32_to_cpu(*(volatile u32 *)(RALINK_REG_GPIOMODE)); 
    gpiomode |= (0x1<<10); 
    *(volatile u32 *)(RALINK_REG_GPIOMODE) = cpu_to_le32(gpiomode); 
}

/** 
* 设置gpio40-gpio71的数据方向. 
*/ 
static void set_7140_dir(int gpio,int dir) 
{ 
    u32 gpiomode; 
    
    gpiomode = le32_to_cpu(*(volatile u32 *)(RALINK_REG_PIO7140DIR)); 
    gpiomode &= ~(0x01<<(gpio-40)); 
    gpiomode |= (dir?0x01:0x0)<<(gpio-40);

    *(volatile u32 *)(RALINK_REG_PIO7140DIR) = cpu_to_le32(gpiomode);    
}

/** 
* 向gpio40-gpio71脚写数据，0 or 1. 
* 每一位对应一个引脚澹(40---71) 
*/ 
static void gpio7140_write_data(int gpio, int data) 
{ 
    unsigned long tmp;

    if(gpio < 40 || gpio > 71) 
        return; 
    
    tmp = le32_to_cpu(*(volatile u32 *)(RALINK_REG_PIO7140DATA)); 
    tmp &= ~(0x01<<(gpio-40));//gpio位置0 
    tmp |= (data?0x01:0x0)<<(gpio-40);//gpio位置data 
    
    *(volatile u32 *)(RALINK_REG_PIO7140DATA) = cpu_to_le32(tmp);

    //printk("write data reg 0x%8x,tmp 0x%8x\n",RALINK_REG_PIO7140DATA,tmp); 
}

/** 
* led常亮. 
*/ 
static void set_led_on(unsigned long gpio) 
{ 
    mutex_lock(&led_mutex);//上锁 
    
    gpio7140_write_data(gpio,1);

    mutex_unlock(&led_mutex);//解锁 
}

/** 
* led常灭. 
*/ 
static void set_led_off(unsigned long gpio) 
{ 
    mutex_lock(&led_mutex);//上锁 
    
    gpio7140_write_data(gpio,0);

    mutex_unlock(&led_mutex);//解锁 
}

long led_driver_ioctl(struct file *filp, unsigned int req, unsigned long arg) 
{ 
    unsigned long gpio, data; 
    
    switch(req) { 
        case SET_LED_ON: 
            if(arg < 40 || arg > 71) 
                return -EINVAL; 
            set_led_on(arg); 
            //printk("[driver]led on,gpio %d.\n",(int)arg); 
            break; 
        case SET_LEN_OF: 
            if(arg < 40 || arg > 71) 
                return -EINVAL; 
            set_led_off(arg); 
            //printk("[driver]led off,gpio %d.\n",(int)arg); 
            break; 
        case SET_LED_DIR: 
            gpio = (arg&0xFFFF0000)>>16; 
            data = arg&0x0FFFF; 
            set_7140_dir(gpio, data); 
            break; 
        default: 
            return -EINVAL; 
            break; 
    } 
    return 0; 
}

static int led_driver_open(struct inode *inode, struct file *file) 
{ 
    return 0; 
}

static int led_driver_close(struct inode *inode, struct file *file) 
{ 
    return 0; 
}

static struct file_operations led_fops = //设备文件描述符 
{ 
    .owner        = THIS_MODULE, 
    .open        = led_driver_open, 
    .release    = led_driver_close, 
    .unlocked_ioctl = led_driver_ioctl, 
};

static struct miscdevice led_misc = //杂项设备 
{ 
    .minor = MISC_DYNAMIC_MINOR,  //动态设备名字 
    .name = LED_DRIVER_NAME, 
    .fops = &led_fops, 
};

static int __init led_driver_init(void) 
{ 
    int ret;

    set_7140_gpio_mode();//set RGMII2_GPIO_MODE to gpio mode.pro.p38 
    
    ret = misc_register(&led_misc); 
    printk("led_driver_init OK!\n"); 
    return ret; 
}

static void __exit led_driver_exit(void) 
{ 
    int ret; 
    
    ret = misc_deregister(&led_misc); 
    if(ret < 0) 
        printk("led_driver_exit error.\n"); 
    printk("led_driver_exit.\n"); 
}

module_init(led_driver_init); 
module_exit(led_driver_exit); 
MODULE_LICENSE("GPL"); 
MODULE_AUTHOR("XYH");