字符设备驱动0：一个简单但完整的字符设备驱动程序

//在驱动入口函数中，使用register_chrdev添加字符设备驱动：

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

#define DEVICE_NAME     "leds"  /* 加载模式后，执行”cat /proc/devices”命令看到的设备名称 */
#define LED_MAJOR       231     /* 主设备号 */

static struct class *leds_class;
static struct class_device    *leds_class_devs[4];

/* bit0<=>D10, 0:亮, 1:灭
*  bit1<=>D11, 0:亮, 1:灭
*  bit2<=>D12, 0:亮, 1:灭
*/
static char leds_status = 0x0;
static DECLARE_MUTEX(leds_lock); // 定义赋值

//static int minor;
static unsigned long gpio_va;

#define GPIO_OFT(x) ((x) - 0x56000000)
#define GPFCON  (*(volatile unsigned long *)(gpio_va + GPIO_OFT(0x56000050)))//oo00:GPFCON  0x56000050  R/W  配置端口F的引脚
#define GPFDAT  (*(volatile unsigned long *)(gpio_va + GPIO_OFT(0x56000054)))//oo00:gpio_va + 0x54 ，把物理地址0x56000054映射为虚拟地址GPFDAT。
//led驱动中，要操作io口，必须要把物理地址映射为虚拟地址。

/* 应用程序对设备文件/dev/leds执行open(...)时，
* 就会调用s3c24xx_leds_open函数
*/
static int s3c24xx_leds_open(struct inode *inode, struct file *file)
{
int minor = MINOR(inode->i_rdev); //MINOR(inode->i_cdev);

switch(minor)
{
case 0: /* /dev/leds */
{
// 配置3引脚为输出
//s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP);
GPFCON &= ~(0x3<<(4*2)); //oo00:这里GPFCON是虚拟地址，在驱动模块开始的时候，这个虚拟地址已经通过宏定义 #define GPFCON  (*(volatile unsigned long *)(gpio_va + GPIO_OFT(0x56000050)))被映射到物理地址
GPFCON |= (1<<(4*2));

//s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP);
GPFCON &= ~(0x3<<(5*2));
GPFCON |= (1<<(5*2));

//s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP);
GPFCON &= ~(0x3<<(6*2));
GPFCON |= (1<<(6*2));

// 都输出0
//s3c2410_gpio_setpin(S3C2410_GPF4, 0);
GPFDAT &= ~(1<<4);

//s3c2410_gpio_setpin(S3C2410_GPF5, 0);
GPFDAT &= ~(1<<5);
//s3c2410_gpio_setpin(S3C2410_GPF6, 0);
GPFDAT &= ~(1<<6);

down(&leds_lock);
leds_status = 0x0;
up(&leds_lock);

break;
}

case 1: /* /dev/led1 */
{
s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP);
s3c2410_gpio_setpin(S3C2410_GPF4, 0);

down(&leds_lock);
leds_status &= ~(1<<0);
up(&leds_lock);

break;
}

case 2: /* /dev/led2 */
{
s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP);
s3c2410_gpio_setpin(S3C2410_GPF5, 0);
leds_status &= ~(1<<1);
break;
}

case 3: /* /dev/led3 */
{
s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP);
s3c2410_gpio_setpin(S3C2410_GPF6, 0);

down(&leds_lock);
leds_status &= ~(1<<2);
up(&leds_lock);

break;
}

}

return 0;
}

static int s3c24xx_leds_read(struct file *filp, char __user *buff,
size_t count, loff_t *offp)
{
int minor = MINOR(filp->f_dentry->d_inode->i_rdev);
char val;

switch (minor)
{
case 0: /* /dev/leds */
{
copy_to_user(buff, (const void *)&leds_status, 1);
break;
}

case 1: /* /dev/led1 */
{
down(&leds_lock);
val = leds_status & 0x1;
up(&leds_lock);
copy_to_user(buff, (const void *)&val, 1);
break;
}

case 2: /* /dev/led2 */
{
down(&leds_lock);
val = (leds_status>>1) & 0x1;
up(&leds_lock);
copy_to_user(buff, (const void *)&val, 1);
break;
}

case 3: /* /dev/led3 */
{
down(&leds_lock);
val = (leds_status>>2) & 0x1;
up(&leds_lock);
copy_to_user(buff, (const void *)&val, 1);
break;
}
}
return 1;
}

static ssize_t s3c24xx_leds_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
//int minor = MINOR(inode->i_rdev); //MINOR(inode->i_cdev);
int minor = MINOR(file->f_dentry->d_inode->i_rdev);
char val;

copy_from_user(&val, buf, 1);

switch (minor)
{
case 0: /* /dev/leds */
{
s3c2410_gpio_setpin(S3C2410_GPF4, (val & 0x1));
s3c2410_gpio_setpin(S3C2410_GPF5, (val & 0x1));
s3c2410_gpio_setpin(S3C2410_GPF6, (val & 0x1));
down(&leds_lock);
leds_status = val;
up(&leds_lock);
break;
}

case 1: /* /dev/led1 */
{
s3c2410_gpio_setpin(S3C2410_GPF4, val);

if (val == 0)
{
down(&leds_lock);
leds_status &= ~(1<<0);
up(&leds_lock);
}
else
{
down(&leds_lock);
leds_status |= (1<<0);
up(&leds_lock);
}
break;
}

case 2: /* /dev/led2 */
{
s3c2410_gpio_setpin(S3C2410_GPF5, val);
if (val == 0)
{
down(&leds_lock);
leds_status &= ~(1<<1);
up(&leds_lock);
}
else
{
down(&leds_lock);
leds_status |= (1<<1);
up(&leds_lock);
}
break;
}

case 3: /* /dev/led3 */
{
s3c2410_gpio_setpin(S3C2410_GPF6, val);
if (val == 0)
{
down(&leds_lock);
leds_status &= ~(1<<2);
up(&leds_lock);
}
else
{
down(&leds_lock);
leds_status |= (1<<2);
up(&leds_lock);
}
break;
}

}

return 1;
}

/* 这个结构是字符设备驱动程序的核心
* 当应用程序操作设备文件时所调用的open、read、write等函数，
* 最终会调用这个结构中指定的对应函数
*/
static struct file_operations s3c24xx_leds_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   =   s3c24xx_leds_open,
.read    =    s3c24xx_leds_read,
.write    =    s3c24xx_leds_write,
};

/*
* 执行insmod命令时就会调用这个函数
*/
static int __init s3c24xx_leds_init(void)
//static int __init init_module(void)

{
int ret;
int minor = 0;

gpio_va = ioremap(0x56000000, 0x100000);
if (!gpio_va) {
return -EIO;
}
printk(DEVICE_NAME "gpio_va = %x\n",gpio_va);

/* 注册字符设备
* 参数为主设备号、设备名字、file_operations结构；
* 这样，主设备号就和具体的file_operations结构联系起来了，
* 操作主设备为LED_MAJOR的设备文件时，就会调用s3c24xx_leds_fops中的相关成员函数
* LED_MAJOR可以设为0，表示由内核自动分配主设备号
*/
ret = register_chrdev(LED_MAJOR, DEVICE_NAME, &s3c24xx_leds_fops);
if (ret < 0) {
printk(DEVICE_NAME " can't register major number\n");
return ret;
}
//oo00 :begin : 分配了四个子设备号  minor == 0 1 2 3
leds_class = class_create(THIS_MODULE, "leds");
if (IS_ERR(leds_class))
return PTR_ERR(leds_class);

leds_class_devs[0] = class_device_create(leds_class, NULL, MKDEV(LED_MAJOR, 0), NULL, "leds");

for (minor = 1; minor < 4; minor++)
{
leds_class_devs[minor] = class_device_create(leds_class, NULL, MKDEV(LED_MAJOR, minor), NULL, "led%d", minor);
if (unlikely(IS_ERR(leds_class_devs[minor])))
return PTR_ERR(leds_class_devs[minor]);
}
//oo00 :end

printk(DEVICE_NAME " initialized\n");
return 0;
}

/*
* 执行rmmod命令时就会调用这个函数
*/
static void __exit s3c24xx_leds_exit(void)
{
int minor;
/* 卸载驱动程序 */
unregister_chrdev(LED_MAJOR, DEVICE_NAME);

for (minor = 0; minor < 4; minor++)
{
class_device_unregister(leds_class_devs[minor]);
}
class_destroy(leds_class);
iounmap(gpio_va);
}

/* 这两行指定驱动程序的初始化函数和卸载函数 */
module_init(s3c24xx_leds_init);
module_exit(s3c24xx_leds_exit);

/* 描述驱动程序的一些信息，不是必须的 */
MODULE_AUTHOR("http://www.100ask.net");
MODULE_VERSION("0.1.0");
MODULE_DESCRIPTION("S3C2410/S3C2440 LED Driver");
MODULE_LICENSE("GPL");

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

/*
*  ledtest <dev> <on|off>
*/

void print_usage(char *file)
{
printf("Usage:\n");
printf("%s <dev> <on|off>\n",file);
printf("eg. \n");
printf("%s /dev/leds on\n", file);
printf("%s /dev/leds off\n", file);
printf("%s /dev/led1 on\n", file);
printf("%s /dev/led1 off\n", file);
}

int main(int argc, char **argv)
{
int fd;
char* filename;
char val;

if (argc != 3)
{
print_usage(argv[0]);
return 0;
}

filename = argv[1];

fd = open(filename, O_RDWR);
if (fd < 0)
{
printf("error, can't open %s\n", filename);
return 0;
}

if (!strcmp("on", argv[2]))
{
// 亮灯
val = 0;
write(fd, &val, 1);
}
else if (!strcmp("off", argv[2]))
{
// 灭灯
val = 1;
write(fd, &val, 1);
}
else
{
print_usage(argv[0]);
return 0;
}

return 0;
}

加载模块后，执行”cat /proc/devices”命令看设备名称;// register_chrdev(LED_MAJOR, DEVICE_NAME, &s3c24xx_leds_fops);

执行ls /dev/ 命令查看class名称。//class_device_create(leds_class, NULL, MKDEV(LED_MAJOR, minor), NULL, "led%d", minor);

附例：

int major;
static int first_drv_init(void)
{
major = register_chrdev(0, "first_drv", &first_drv_fops); // 注册, 告诉内核

firstdrv_class = class_create(THIS_MODULE, "firstdrv");

firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, 0), NULL, "xyz"); /* /dev/xyz */

gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
gpfdat = gpfcon + 1;

return 0;
}
---------------------------------
# cat /proc/devices
Character devices:
1 mem
2 pty
204 s3c2410_serial
252 first_drv
254 rtc

# ls -l /dev
crw-rw----    1 0        0        204,  64 Jan  1 00:56 s3c2410_serial0
crw-rw----    1 0        0        204,  65 Jan  1 00:00 s3c2410_serial1
crw-rw----    1 0        0        204,  66 Jan  1 00:00 s3c2410_serial2
crw-rw----    1 0        0        252,   0 Jan  1 00:44 xyz
-------------------------------------
fd = open("/dev/xyz", O_RDWR);
if (fd < 0)
{
printf("can't open!\n");
}

参考：

linux设备驱动程序之简单字符设备驱动 【很详细】http://www.cnblogs.com/geneil/archive/2011/12/03/2272869.html