我們基于寄存器的方式已經編寫了LED驅動，實現點亮/熄滅LED，但是你有沒有發現一個問題，就是假設LED修改了一個GPIO，那么需要對應的修改寄存器代碼，非常繁瑣，而且隨著改板次數增加，那么會帶來一個災難性的重復性沒有技術含量的重復工作的弊端。
在之前的文檔我們已經介紹了LED寄存器實現方式：https://blog.csdn.net/XiaoXiaoPengBo/article/details/128684419?spm=1001.2014.3001.5501
并且我們之前文檔也寫過了設備樹相關的概念內容：
https://blog.csdn.net/XiaoXiaoPengBo/article/details/128734828?spm=1001.2014.3001.5501
那么本節，我們就結合之前的內容把他利用起來！！！我們還是用之前的LED GPIO1_3
在根節點下增加一下內容
wireless_link_led{
#address-cells = <1>;
#size-cells = <1>;
compatible = "wl_led";
status = "ok";
reg = < 0X020C406C 0X04 /* CCM_CCGR1_BASE */
0X020E0068 0X04 /* SW_MUX_GPIO1_IO03_BASE */
0X020E02F4 0X04 /* SW_PAD_GPIO1_IO03_BASE */
0X0209C000 0X04 /* GPIO1_DR_BASE */
0X0209C004 0X04 >; /* GPIO1_GDIR_BASE */
};
make dtbs
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/of_address.h>
#include <linux/of.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#define LED_MAJOR 200
#define LED_NAME "led"
static struct class *led_class;
struct device_node *led_nd;
static void __iomem *IMX6U_CCM_CCGR1;
static void __iomem *SW_MUX_GPIO1_IO03;
static void __iomem *SW_PAD_GPIO1_IO03;
static void __iomem *GPIO1_DR;
static void __iomem *GPIO1_GDIR;
static int led_open(struct inode *inode, struct file *filp)
{
printk("led_open\r\n");
return 0;
}
static ssize_t led_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{
printk("led_read\r\n");
return 0;
}
static ssize_t led_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
printk("led_write\r\n");
int retvalue;
u32 val = 0;
unsigned char databuf[1];
unsigned char ledstat;
retvalue = copy_from_user(databuf, buf, cnt);
if(retvalue < 0) {
printk("kernel write failed!\r\n");
return -EFAULT;
}
ledstat = databuf[0];
printk("ledstat:%d\r\n",ledstat);
if(ledstat == 1)
{
val = readl(GPIO1_DR);
val &= ~(1 << 3);
writel(val, GPIO1_DR);
}
else if(ledstat == 0)
{
val = readl(GPIO1_DR);
val|= (1 << 3);
writel(val, GPIO1_DR);
}
return 1;
}
static int led_release(struct inode *inode, struct file *filp)
{
printk("led_release\r\n");
return 0;
}
static struct file_operations led_fops = {
.owner = THIS_MODULE,
.open = led_open,
.read = led_read,
.write = led_write,
.release = led_release,
};
static int __init led_driver_init(void)
{
u8 index;
u32 val = 0;
int ret = 0;
const char *str;
u32 regdata[14];
struct property *proper;
printk("led_driver_init\r\n");
led_nd = of_find_node_by_path("/wireless_link_led");
if(led_nd)
printk("led nd found\r\n");
else
{
printk("led nd is not found\r\n");
return -1;
}
proper = of_find_property(led_nd, "compatible", NULL);
if(proper)
printk("compatible = %s\r\n", (char*)proper->value);
else
printk("compatible property find failed\r\n");
ret = of_property_read_string(led_nd, "status", &str);
printk("of_property_read_string ret:%d\r\n",ret);
if(ret >= 0)
printk("status = %s\r\n",str);
ret = of_property_read_u32_array(led_nd, "reg", regdata, 10);
printk("of_property_read_string ret:%d\r\n",ret);
printk("---------------------------\r\n");
for(index = 0; index < 10; index )
printk("%#X ", regdata[index]);
printk("\r\n---------------------------\r\n");
IMX6U_CCM_CCGR1 = of_iomap(led_nd, 0);
SW_MUX_GPIO1_IO03 = of_iomap(led_nd, 1);
SW_PAD_GPIO1_IO03 = of_iomap(led_nd, 2);
GPIO1_DR = of_iomap(led_nd, 3);
GPIO1_GDIR = of_iomap(led_nd, 4);
val = readl(IMX6U_CCM_CCGR1);
val &= ~(3 << 26);
val |= (3 << 26);
writel(val, IMX6U_CCM_CCGR1);
writel(5, SW_MUX_GPIO1_IO03);
writel(0x10B0, SW_PAD_GPIO1_IO03);
val = readl(GPIO1_GDIR);
val &= ~(1 << 3);
val |= (1 << 3);
writel(val, GPIO1_GDIR);
val = readl(GPIO1_DR);
val |= (1 << 3);
writel(val, GPIO1_DR);
ret = register_chrdev(LED_MAJOR, LED_NAME, &led_fops);
if(ret < 0){
printk("register chrdev failed!\r\n");
return -EIO;
}
led_class = class_create(THIS_MODULE,"led_class");
device_create(led_class,NULL,MKDEV(LED_MAJOR,0),NULL,"led"); /* /dev/led */
return 0;
}
static void __exit led_driver_exit(void)
{
printk("led_driver_exit\r\n");
iounmap(IMX6U_CCM_CCGR1);
iounmap(SW_MUX_GPIO1_IO03);
iounmap(SW_PAD_GPIO1_IO03);
iounmap(GPIO1_DR);
iounmap(GPIO1_GDIR);
device_destroy(led_class,MKDEV(LED_MAJOR,0));
class_destroy(led_class);
unregister_chrdev(LED_MAJOR, LED_NAME);
}
module_init(led_driver_init);
module_exit(led_driver_exit);
MODULE_LICENSE("GPL"); #include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
int main(int argc, char *argv[])
{
int fd;
int ret;
uint8_t led;
fd = open(argv[1], O_RDWR);
if(!strcmp("led_on",argv[2]))
{
printf("led on\r\n");
led = 1;
write(fd,&led,sizeof(led));
}
if(!strcmp("led_off",argv[2]))
{
led = 0;
printf("led on\r\n");
write(fd,&led,sizeof(led));
}
close(fd);
}點亮 LED燈 ./test_app /dev/led led_on
熄滅 LED燈 ./test_app /dev/led led_on
其實到了這一步雖然不需要配對寄存器地址，但是代碼還在編寫寄存器代碼，也就是說換了一個GPIO還是要修改代碼，是的！！！別急，后續我們看了GPIO子系統以及pinctl子系統后相信會有答案！！！
