思路:
代码实现基于imx6ull
驱动程序虽然可以操作硬件,但是也不能直接使用寄存器地址,要通过ioremap()函数映射为虚拟地址操作
驱动程序 leddrv.c
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/wait.h>
#include <linux/uaccess.h>
#include <linux/device.h>
#include <asm/io.h>
static int major;
static struct class *led_class;
/* registers */
// IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 地址:0x02290000 + 0x14
static volatile unsigned int *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3;
// GPIO5_GDIR 地址:0x020AC004
static volatile unsigned int *GPIO5_GDIR;
//GPIO5_DR 地址:0x020AC000
static volatile unsigned int *GPIO5_DR;
static ssize_t led_write(struct file *filp, const char __user *buf,
size_t count, loff_t *ppos)
{
char val;
int ret;
/* copy_from_user : get data from app */
ret = copy_from_user(&val, buf, 1);
/* to set gpio register: out 1/0 */
if (val)
{
/* set gpio to let led on */
*GPIO5_DR &= ~(1<<3);
}
else
{
/* set gpio to let led off */
*GPIO5_DR |= (1<<3);
}
return 1;
}
static int led_open(struct inode *inode, struct file *filp)
{
/* enable gpio5
* configure gpio5_io3 as gpio
* configure gpio5_io3 as output
*/
*IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 &= ~0xf;
*IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 |= 0x5;
*GPIO5_GDIR |= (1<<3);
return 0;
}
static struct file_operations led_fops = {
.owner = THIS_MODULE,
.write = led_write,
.open = led_open,
};
/* 入口函数 */
static int __init led_init(void)
{
printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);
major = register_chrdev(0, "100ask_led", &led_fops);
/* ioremap */
// IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 地址:0x02290000 + 0x14
IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3 = ioremap(0x02290000 + 0x14, 4);
// GPIO5_GDIR 地址:0x020AC004
GPIO5_GDIR = ioremap(0x020AC004, 4);
//GPIO5_DR 地址:0x020AC000
GPIO5_DR = ioremap(0x020AC000, 4);
led_class = class_create(THIS_MODULE, "myled");
device_create(led_class, NULL, MKDEV(major, 0), NULL, "myled"); /* /dev/myled */
return 0;
}
static void __exit led_exit(void)
{
iounmap(IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3);
iounmap(GPIO5_GDIR);
iounmap(GPIO5_DR);
device_destroy(led_class, MKDEV(major, 0));
class_destroy(led_class);
unregister_chrdev(major, "100ask_led");
}
module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
测试程序
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
// ledtest /dev/myled on
// ledtest /dev/myled off
int main(int argc, char **argv)
{
int fd;
char status = 0;
if (argc != 3)
{
printf("Usage: %s <dev> <on|off>\n", argv[0]);
printf(" eg: %s /dev/myled on\n", argv[0]);
printf(" eg: %s /dev/myled off\n", argv[0]);
return -1;
}
// open
fd = open(argv[1], O_RDWR);
if (fd < 0)
{
printf("can not open %s\n", argv[0]);
return -1;
}
// write
if (strcmp(argv[2], "on") == 0)
{
status = 1;
}
write(fd, &status, 1);
return 0;
}