韦东山嵌入式驱动学习-----LED驱动

1.LED驱动框架
LED驱动
把驱动拆分为通用的框架(leddrv.c)、具体的硬件操作(board_X.c)
抽象出一个led_operations 结构体, 每个单板相关的 board_X.c 实现自己的 led_operations 结构体，供上层的 leddrv.c 调用.编译时将通用的框架.c和单板自己的框架.c编译成一个ko文件

代码思路
核心流程“：

定义自己的file_operations结构体
static struct file_operations led_drv = 
{
	.owner	 = THIS_MODULE,
	.open    = led_drv_open,
	.read    = led_drv_read,
	.write   = led_drv_write,
	.release = led_drv_close,
};


APP调用open函数，调用通用驱动中的open
static int led_drv_open (struct inode *node, struct file *file)
根据次设备号初始化 LED 调用个体硬件的初始化函数
p_led_opr->init(minor);

个体硬件实现自己的初始化函数
static int board_demo_led_init (int which) /* 初始化LED, which-哪个LED */
.init = board_demo_led_init,
.ctl  = board_demo_led_ctl,

APP调用write函数
根据传入的次设备号和status控制LED 
	p_led_opr->ctl(minor, status);


卸载驱动程序时，就会去调用这个出口函数
static void __exit led_exit(void)

核心流程
在这里实现通用驱动框架需要调用的函数

构造了一个 led_operations 结构体，用来表示 LED 的硬件操作
static struct led_operations board_demo_led_opr = 
{				
.num = 4,
.init = board_demo_led_init,
.ctl = board_demo_led_ctl,
};

static int board_demo_led_init (int which)
{
		判断初始化哪个LED，对相应的引脚始能
1.enable GPIO5
 2. set GPIO5_IO03 as GPIO
 3. set GPIO5_IO03 as output
}
实现特定硬件的控制函数，根据参数设置 LED 引脚的输出电平
static  int  board_demo_led_ctl  (int  which,  char  status)
{
if (status) /* on : output 0 */
 gpio5->dr &= ~(1<<3);
else   /* on : output 1 */
gpio5->dr |= (1<<3);
 }

get_board_led_opr 函数供上层调用，给上层提供 led_operations 结构体：
struct led_operations *get_board_led_opr(void)
{
return &board_demo_led_opr;  
}

2.完整代码

leddrv.c

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>

#include "led_opr.h"


/* 1. 确定主设备号                                                                 */
static int major = 0;
static struct class *led_class;
struct led_operations *p_led_opr;


#define MIN(a, b) (a < b ? a : b)

/* 3. 实现对应的open/read/write等函数，填入file_operations结构体                   */
static ssize_t led_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	return 0;
}

/* write(fd, &val, 1); */
static ssize_t led_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
	int err;
	char status;
	struct inode *inode = file_inode(file);
	int minor = iminor(inode);
	
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	err = copy_from_user(&status, buf, 1);

	/* 根据次设备号和status控制LED */
	p_led_opr->ctl(minor, status);
	
	return 1;
}

static int led_drv_open (struct inode *node, struct file *file)
{
	int minor = iminor(node);
	
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	/* 根据次设备号初始化LED */
	p_led_opr->init(minor);
	
	return 0;
}

static int led_drv_close (struct inode *node, struct file *file)
{
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	return 0;
}

/* 2. 定义自己的file_operations结构体                                              */
static struct file_operations led_drv = {
	.owner	 = THIS_MODULE,
	.open    = led_drv_open,
	.read    = led_drv_read,
	.write   = led_drv_write,
	.release = led_drv_close,
};

/* 4. 把file_operations结构体告诉内核：注册驱动程序                                */
/* 5. 谁来注册驱动程序啊？得有一个入口函数：安装驱动程序时，就会去调用这个入口函数 */
static int __init led_init(void)
{
	int err;
	int i;
	
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
	major = register_chrdev(0, "100ask_led", &led_drv);  /* /dev/led */


	led_class = class_create(THIS_MODULE, "100ask_led_class");
	err = PTR_ERR(led_class);
	if (IS_ERR(led_class)) {
		printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
		unregister_chrdev(major, "led");
		return -1;
	}

	p_led_opr = get_board_led_opr();

	for (i = 0; i < p_led_opr->num; i++)
		device_create(led_class, NULL, MKDEV(major, i), NULL, "100ask_led%d", i); /* /dev/100ask_led0,1,... */

	
	return 0;
}

/* 6. 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数           */
static void __exit led_exit(void)
{
	int i;
	printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);

	for (i = 0; i < p_led_opr->num; i++)
		device_destroy(led_class, MKDEV(major, i)); /* /dev/100ask_led0,1,... */

	device_destroy(led_class, MKDEV(major, 0));
	class_destroy(led_class);
	unregister_chrdev(major, "100ask_led");
}


/* 7. 其他完善：提供设备信息，自动创建设备节点                                     */

module_init(led_init);
module_exit(led_exit);

MODULE_LICENSE("GPL");

led_opr.h 供leddrv.c使用 其中定义的init ctl方法在board_100ask_imx6ull.c中实现

#ifndef _LED_OPR_H
#define _LED_OPR_H

struct led_operations {
	int num;
	int (*init) (int which); /* 初始化LED, which-哪个LED */       
	int (*ctl) (int which, char status); /* 控制LED, which-哪个LED, status:1-亮,0-灭 */
};

struct led_operations *get_board_led_opr(void);


#endif

board_100ask_imx6ull.c 单板对应的底层驱动

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include <asm/io.h>

#include "led_opr.h"

static volatile unsigned int *CCM_CCGR1                              ;
static volatile unsigned int *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3;
static volatile unsigned int *GPIO5_GDIR                             ;
static volatile unsigned int *GPIO5_DR                               ;

static int board_demo_led_init (int which) /* 初始化LED, which-哪个LED */       
{
    unsigned int val;

    //printk("%s %s line %d, led %d\n", __FILE__, __FUNCTION__, __LINE__, which);
    if (which == 0)
    {
        if (!CCM_CCGR1)
        {
            CCM_CCGR1                               = ioremap(0x20C406C, 4);
            IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 = ioremap(0x2290014, 4);
            GPIO5_GDIR                              = ioremap(0x020AC000 + 0x4, 4);
            GPIO5_DR                                = ioremap(0x020AC000 + 0, 4);
        }
        
        /* GPIO5_IO03 */
        /* a. 使能GPIO5
         * set CCM to enable GPIO5
         * CCM_CCGR1[CG15] 0x20C406C
         * bit[31:30] = 0b11
         */
        *CCM_CCGR1 |= (3<<30);
        
        /* b. 设置GPIO5_IO03用于GPIO
         * set IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3
         *      to configure GPIO5_IO03 as GPIO
         * IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3  0x2290014
         * bit[3:0] = 0b0101 alt5
         */
        val = *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3;
        val &= ~(0xf);
        val |= (5);
        *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 = val;
        
        
        /* b. 设置GPIO5_IO03作为output引脚
         * set GPIO5_GDIR to configure GPIO5_IO03 as output
         * GPIO5_GDIR  0x020AC000 + 0x4
         * bit[3] = 0b1
         */
        *GPIO5_GDIR |= (1<<3);
    }
    
    return 0;
}

static int board_demo_led_ctl (int which, char status) /* 控制LED, which-哪个LED, status:1-亮,0-灭 */
{
    //printk("%s %s line %d, led %d, %s\n", __FILE__, __FUNCTION__, __LINE__, which, status ? "on" : "off");
    if (which == 0)
    {
        if (status) /* on: output 0*/
        {
            /* d. 设置GPIO5_DR输出低电平
             * set GPIO5_DR to configure GPIO5_IO03 output 0
             * GPIO5_DR 0x020AC000 + 0
             * bit[3] = 0b0
             */
            *GPIO5_DR &= ~(1<<3);
        }
        else  /* off: output 1*/
        {
            /* e. 设置GPIO5_IO3输出高电平
             * set GPIO5_DR to configure GPIO5_IO03 output 1
             * GPIO5_DR 0x020AC000 + 0
             * bit[3] = 0b1
             */ 
            *GPIO5_DR |= (1<<3);
        }
    
    }
    return 0;
}

//构造了一个 led_operations 结构体，用来表示 LED 的硬件操作：
//led_operations 结构体中有 init 函数指针，它指向 board_demo_led_init 函数，在里面将会初始化
//LED 引脚：使能、设置为 GPIO 模式、设置为输出引脚。
//led_operations 结构体中有 ctl 函数指针，它指向 board_demo_led_ctl 函数，在里面将会根据参数设
//置 LED 引脚的输出电平：

static struct led_operations board_demo_led_opr = {
    .num  = 1,
    .init = board_demo_led_init,
    .ctl  = board_demo_led_ctl,
};


// get_board_led_opr 函数供上层调用，给上层提供 led_operations 结构体：
struct led_operations *get_board_led_opr(void)
{
    return &board_demo_led_opr;
}

ledtest.c 测试程序

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

/*
 * ./ledtest /dev/100ask_led0 on
 * ./ledtest /dev/100ask_led0 off
 */
int main(int argc, char **argv)
{
	int fd;
	char status;
	
	/* 1. 判断参数 */
	if (argc != 3) 
	{
		printf("Usage: %s <dev> <on | off>\n", argv[0]);
		return -1;
	}

	/* 2. 打开文件 */
	fd = open(argv[1], O_RDWR);
	if (fd == -1)
	{
		printf("can not open file %s\n", argv[1]);
		return -1;
	}

	/* 3. 写文件 */
	if (0 == strcmp(argv[2], "on"))
	{
		status = 1;
		write(fd, &status, 1);
	}
	else
	{
		status = 0;
		write(fd, &status, 1);
	}
	
	close(fd);
	
	return 0;
}

makelife

# 1. 使用不同的开发板内核时, 一定要修改KERN_DIR
# 2. KERN_DIR中的内核要事先配置、编译, 为了能编译内核, 要先设置下列环境变量:
# 2.1 ARCH,          比如: export ARCH=arm64
# 2.2 CROSS_COMPILE, 比如: export CROSS_COMPILE=aarch64-linux-gnu-
# 2.3 PATH,          比如: export PATH=$PATH:/home/book/100ask_roc-rk3399-pc/ToolChain-6.3.1/gcc-linaro-6.3.1-2017.05-x86_64_aarch64-linux-gnu/bin 
# 注意: 不同的开发板不同的编译器上述3个环境变量不一定相同,
#       请参考各开发板的高级用户使用手册

KERN_DIR = /home/ky/100ask_imx6ull-sdk/Linux-4.9.88

all:
	make -C $(KERN_DIR) M=`pwd` modules 
	$(CROSS_COMPILE)gcc -o ledtest ledtest.c 

clean:
	make -C $(KERN_DIR) M=`pwd` modules clean
	rm -rf modules.order
	rm -f ledtest

# 参考内核源码drivers/char/ipmi/Makefile
# 要想把a.c, b.c编译成ab.ko, 可以这样指定:
# ab-y := a.o b.o
# obj-m += ab.o

# leddrv.c board_100ask_imx6ull.c 编译成 100ask_led.ko
100ask_led-y := leddrv.o board_100ask_imx6ull.o
obj-m	+= 100ask_led.o

测试

在开发板上执行

insmod 100ask_led.ko
./ledtest /dev/100ask_led0 on
./ledtest /dev/100ask_led0 off