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。
设备树操作
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
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
3.添加一个设备节点
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 <linux/gpio/consumer.h> // descriptor-based
驱动代码
#include <linux/module.h>
#include <linux/platform_device.h>#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
#include <linux/gpio/consumer.h>
#include <linux/of.h>/* 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");
