这两个系统属于软件层,让我们不用直接对硬件配置,一般由芯片出产商写好,我们只要基于它们改就行。
1.使用官方的工具来编写pinctrl设置gpio的设备树代码。
如图,生成代码
![在这里插入图片描述](https://img-blog.csdnimg.cn/b3a6ab2177014f73a43c1ea1e5f0aa14.png
2.将生成的代码复制带设备树文件中,并修改子节点名字位myled_gpio_for_sys
pinctrl-names:“default”,表示只有一个状态
pinctrl-0 = "&myled_gpio_for_sys"表示当设备处于第一个状态时,引脚按照myled_gpio_for_sys子节点的属性来复用。
led-gpios = <&gpio5 3 GPIO_ACTIVE_LOW> 用来描述LED引脚
参数:
&gpio5 表示CD引脚所使用的IO属于GPIO5组
3 表示GPIO5组的第3号IO
GPIO_ACTIVE_LOW 表示低电平有效
最后就可以在驱动代码中获得、设置、读写GPIO引脚,
记得包含头文件
#include // descriptor-based
#include
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/* 1. 确定主设备号 */
static int major = 0;
static struct class *led_class;
static struct gpio_desc *led_gpio;
/* 3. 实现对应的open/read/write等函数,填入file_operations结构�? */
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 */
gpiod_set_value(led_gpio, status);
return 1;
}
static int led_drv_open (struct inode *node, struct file *file)
{
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
/* 根据次设备号初始化LED */
gpiod_direction_output(led_gpio, 0);
return 0;
}
static int led_drv_close (struct inode *node, struct file *file)
{
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
return 0;
}
/* 定义自己的file_operations结构�? */
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. 从platform_device获得GPIO
* 把file_operations结构体告诉内核:注册驱动程序
*/
static int chip_demo_gpio_probe(struct platform_device *pdev)
{
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
/* 4.1 设备树中定义�? led-gpios=<...>; */
led_gpio = gpiod_get(&pdev->dev, "led", 0);
if (IS_ERR(led_gpio)) {
dev_err(&pdev->dev, "Failed to get GPIO for led\n");
return PTR_ERR(led_gpio);
}
/* 4.2 注册file_operations */
major = register_chrdev(0, "100ask_led", &led_drv); /* /dev/led */
led_class = class_create(THIS_MODULE, "100ask_led_class");
if (IS_ERR(led_class)) {
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
unregister_chrdev(major, "led");
gpiod_put(led_gpio);
return PTR_ERR(led_class);
}
device_create(led_class, NULL, MKDEV(major, 0), NULL, "100ask_led%d", 0); /* /dev/100ask_led0 */
return 0;
}
static int chip_demo_gpio_remove(struct platform_device *pdev)
{
device_destroy(led_class, MKDEV(major, 0));
class_destroy(led_class);
unregister_chrdev(major, "100ask_led");
gpiod_put(led_gpio);
}
static const struct of_device_id ask100_leds[] = {
{ .compatible = "100ask,leddrv" },
{ },
};
/* 1. 定义platform_driver */
static struct platform_driver chip_demo_gpio_driver = {
.probe = chip_demo_gpio_probe,
.remove = chip_demo_gpio_remove,
.driver = {
.name = "100ask_led",
.of_match_table = ask100_leds,
},
};
/* 2. 在入口函数注册platform_driver */
static int __init led_init(void)
{
int err;
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
err = platform_driver_register(&chip_demo_gpio_driver);
return err;
}
/* 3. 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�? * 卸载platform_driver
*/
static void __exit led_exit(void)
{
printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
platform_driver_unregister(&chip_demo_gpio_driver);
}
/* 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");