确定引脚并生成设备树节点

NXP公司对于IMX6ULL芯片，有设备树生成工具。安装Pins_Tool_for_i.MX_Process_v6_x64.exe后运行，打开IMX6ULL的配置文件MCIMX62Y2xx08.mex就可以在GUI界面中选择引脚，配置它的功能，这就i可以自动生成Pinctrl的子节点信息。

100ASK_IMX6ULL使用的LED原理图如下，可知因骄傲是GPIO5_3：

然而不幸的是我只有野火的板子，而野火的板子的LED居然IO口也是一样的：

可以使用NXP的设备树工具纪念性配置，然后把配置出来的代码放在内核源码里。

在pinctrol中设置引脚的配置信息：

&iomuxc_snvs {//....imx6ul-evk {myled_for_gpio_subsys: myled_for_gpio_subsys{fsl,pins = <MX6ULL_PAD_SNVS_TAMPER3__GPIO5_IO03 0x000110A0>;};//....}

然后添加led的设备节点：

myled {compatible = "100ask,leddrv";pinctrl-names = "default";pinctrl-0 = <&myled_for_gpio_subsys>;led-gpios = <&gpio5 3 GPIO_ACTIVE_LOW>;};

编译程序

#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/errno.h>#include <linux/major.h>#include <linux/init.h>#include <linux/device.h>#include <linux/miscdevice.h>#include <linux/uaccess.h>#include <linux/gpio/consumer.h>#include <linux/of.h>#include <linux/platform_device.h>static int major = 0;static struct class *led_class;struct gpio_desc *led_gpio;static int led_drv_open(struct inode *node, struct file *file){printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);gpiod_direction_output(led_gpio, 0);return 0;}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;}static ssize_t led_drv_write(struct file *file, const char __user *buf, size_t size, loff_t *offset){int err;char status;printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);err = copy_from_user(&status, buf, 1);printk("write status:%x \n", status);gpiod_set_value(led_gpio, status);return 1;}static int led_drv_close(struct inode *node, struct file *file){printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);return 0;}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,};static const struct of_device_id myleds[] = {{.compatible = "100ask,leddrv"},{},};static int chip_demoo_gpio_probe(struct platform_device *pdev){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);}major = register_chrdev(0, "myled", &led_drv);led_class = class_create(THIS_MODULE, "led_class");if(IS_ERR(led_class)) {unregister_chrdev(major, "myled");gpiod_put(led_gpio);printk(KERN_WARNING "class create failed\n");return PTR_ERR(led_class);}device_create(led_class, NULL, MKDEV(major, 0), NULL, "myled%d", 0);return 0;}static int chip_demoo_gpio_remove(struct platform_device *pdev){device_destroy(led_class, MKDEV(major, 0));class_destroy(led_class); unregister_chrdev(major, "myled");gpiod_put(led_gpio);return 0;}static struct platform_driver chip_demoo_gpio_driver = {.probe = chip_demoo_gpio_probe,.remove = chip_demoo_gpio_remove,.driver = {.name = "myled",.of_match_table = myleds,},};static int __init led_drv_init(void){int err;err = platform_driver_register(&chip_demoo_gpio_driver);printk("%s %sled_drv_init\n", __FILE__, __FUNCTION__);return 0;}static void __exit led_drv_exit(void){printk("%s %sled_drv_exit\n", __FILE__, __FUNCTION__);platform_driver_unregister(&chip_demoo_gpio_driver);}module_init(led_drv_init);module_exit(led_drv_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("chen");

app:

#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>#include <string.h>void showUsage(void){printf("app [dev_path] [on,off]\n");}int main(int argc, char *argv[]){char status;if(argc < 3) {showUsage();return -1;}int fd = open(argv[1], O_RDWR);if(fd < 0) {printf("app open device failed path:%s", argv[1]);return -1;}if(0 == strcmp(argv[2], "on")) {status = 1;int ret = write(fd, &status, 1);if(ret <= 0) {printf("app write device fialed %s",argv[2]);return -1;} else {printf("app write device %x", status);}} else if(0 == strcmp(argv[2], "off")) {status = 0;int ret = write(fd, &status, 1);if(ret <= 0) {printf("app write device fialed %s",argv[2]);return -1;} else {printf("app write device %x", status);}}return 0;}