怎么写一个驱动:
1、框架
2、完善硬件的操作
https://blog.csdn.net/qq_40674996/article/details/101059332
(1)看原理图,确定引脚
(2)看芯片手册,控制和设置引脚
(3)写代码
单片机是直接操作物理地址, 而驱动程序是操作虚拟地址。
一、框架:
#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>
static struct class *firstdrv_class;
static struct class_device *firstdrv_class_dev;
volatile unsigned long* gpfcon = NULL;
volatile unsigned long* gpfdat = NULL;
static int first_drv_open(struct inode *inode, struct file *file)
{
return 0;
}
static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
return 0;
}
static struct file_operations first_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 = first_drv_open,
.write = first_drv_write,
};
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 */
return 0;
}
static void first_drv_exit(void)
{
unregister_chrdev(major, "first_drv"); // 卸载
class_device_unregister(firstdrv_class_dev);
class_destroy(firstdrv_class);
}
module_init(first_drv_init);
module_exit(first_drv_exit);
MODULE_LICENSE("GPL");
}
二、将一个IO地址空间映射到内核的虚拟地址空间上去
void * __ioremap(unsigned long phys_addr, unsigned long size, unsigned long flags)
void *ioremap(unsigned long phys_addr, unsigned long size)
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); //映射16个字节
gpfdat = gpfcon + 1;
return 0;
}
static void second_drv_exit(void)
{
unregister_chrdev(major, "second_drv");
class_device_unregister(firstdrv_class_dev);
class_destroy(firstdrv_class);
iounmap(gpfcon);
return 0;
}
三、配置引脚
static int first_drv_open(struct inode *inode, struct file *file)
{
/* 配置GPF4,5,6为输出 */
*gpfcon &= ~((0x3 << 8) | (0x3 << 10) | (0x3 << 12));
*gpfcon |= ((0x1 << 8) | (0x1 << 10) | (0x1 << 12));
return 0;
}
四、通过用户程序传的值来控制LED的亮灭
功能:用于将用户空间的数据传送到内核空间。
unsigned long copy_from_user(void * to, const void __user * from, unsigned long n)
第一个参数to是内核空间的数据目标地址指针,
第二个参数from是用户空间的数据源地址指针,
第三个参数n是数据的长度。
如果数据拷贝成功,则返回零;否则,返回没有拷贝成功的数据字节数。
此函数将from指针指向的用户空间地址开始的连续n个字节的数据产送到to指针指向的内核空间地址
static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
int val;
copy_from_user(&val, buf, count); // copy_to_user();
if(val == 1)
{
*gpfdat &= ~((1 << 4) | (1 << 5) | (1 << 6))
}
else
{
*gpfdat |= ((1 << 4) | (1 << 5) | (1 << 6))
}
return 0;
}
五、用户程序的编写
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
/* firstdrvtest on
* firstdrvtest off
*/
int main(int argc, char **argv)
{
int fd;
int val;
fd = open("/dev/xyz", O_RDWR);
if(fd < 0)
{
printf("can't open!\n");
return -1;
}
if(argc != 2)
{
printf("Usage:\n");
printf("%s < on|off >", argv[0]);
return 0;
}
if(strcmp(argv[1], "on") == 0)
{
val = 1;
}
else
{
val = 0;
}
write(fd, &val, 4);
return 0;
}
六、上面的程序是 一起控制三盏灯,现在分别控制一盏灯
方法一: 和上面一样,通过val 等于1亮第一盏灯,等于2 亮第二盏
方法二:MINOR 返回设备的次驱动号, 根据次驱动号来判断是哪盏灯(参考myleds.c)
主设备号是用来在内核chrdev数组里找到那个驱动;而次设备号,想让次设备号代表什么意思,由程序员管理,。
myleds.c
#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)))
#define GPFDAT (*(volatile unsigned long *)(gpio_va + GPIO_OFT(0x56000054)))
/* 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));
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;
}
/* 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;
}
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"); /* /dev/leds */
for (minor = 1; minor < 4; minor++) /* /dev/led1,2,3 */
{
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]);
}
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");
ledtest.c
#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;
}
运行命令: