平台设备驱动之gpio子系统（写驱动实现在/sys/...目录下用echo命令点灯）

linux__driver_0">1、关键函数（include/linux 及 driver目录下）

	module_platform_driver(leds_drv);   //平台设备驱动入口//获取匹配成功后设备树节点中的 property
	of_get_named_gpio_flags(node, "led_gpio", 0, &flags);  //在/sys/目录下创建文件供操作，第一个参数相当于设备地址，第二个是待创建的与设备对应的文件名
	sysfs_create_file(&dev->kobj, &gpio_attr[i].attr);   	// 用于向文件写数据											
	gpio_direction_output(gpio_dev_pointer->led_gpio, gpio_dev_pointer->led_gpio_output); //用于读取文件数据
	gpio_get_value(gpio_dev_pointer->smoke_sensor_gpio);

2、驱动完整代码

#include <linux/init.h>                        
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/err.h>#include <linux/of_gpio.h>
#include <linux/gpio.h>#include <linux/platform_device.h>
#include <asm/io.h>#include <dt-bindings/gpio/gpio.h>#ifdef CONFIG_OF
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#endifstruct gpio_dev{struct platform_device *pdev;int led_gpio;int led_gpio_output;int smoke_sensor_gpio;
};struct gpio_dev * gpio_dev_pointer = NULL;static ssize_t led_store(struct device *dev, struct device_attribute *attr,const char *buf, size_t count) {//写文件,控制 gpio 输出 （ echo 1 >   led_gpio)                if (buf[0] == '0') {gpio_dev_pointer->led_gpio_output = 0;gpio_direction_output(gpio_dev_pointer->led_gpio, gpio_dev_pointer->led_gpio_output);}else if (buf[0] == '1') {gpio_dev_pointer->led_gpio_output = 1;gpio_direction_output(gpio_dev_pointer->led_gpio, gpio_dev_pointer->led_gpio_output);}    printk(KERN_ERR "led_gpio_store %c \n",gpio_dev_pointer->led_gpio_output);   return count;
}static ssize_t smoke_sensor_show(struct device *dev, struct device_attribute *attr,char *buf){  int sensor_value = 0;sensor_value = gpio_get_value(gpio_dev_pointer->smoke_sensor_gpio);//cat smoke_sensor_gpio时会触发return snprintf(buf, PAGE_SIZE, "%d\n",sensor_value);
}static struct device_attribute gpio_attr[] = {  __ATTR(led_gpio, 0664, NULL, led_store), //写：关联属性文件的写回调函数(*store)  echo时触发__ATTR(smoke_sensor_gpio, 0664, smoke_sensor_show,NULL), //读：关联属性文件的读回调函数(*show)  cat 时触发
};static int gpio_init_sysfs(struct device *dev)
{int i, ret;for(i = 0; i < ARRAY_SIZE(gpio_attr); i++){ret = sysfs_create_file(&dev->kobj, &gpio_attr[i].attr);if(ret){dev_err(dev, "create charger node(%s) error\n",gpio_attr[i].attr.name);return -1;}			}return 0;
}static int gpio_remove_sysfs(struct device *dev)
{int i;for(i = 0; i < ARRAY_SIZE(gpio_attr); i++){sysfs_remove_file(&dev->kobj, &gpio_attr[i].attr);}return 0;
}static int get_OF_node_property(struct gpio_dev *pdata){int gpio;int ret;enum of_gpio_flags flags;struct device *dev = &pdata->pdev->dev;struct device_node *node = dev->of_node;gpio = of_get_named_gpio_flags(node, "led_gpio", 0, &flags);if(gpio_is_valid(gpio)){pdata->led_gpio = gpio;pdata->led_gpio_output = (flags == GPIO_ACTIVE_HIGH)?1:0;printk(KERN_ERR"led_gpio: %d\n", pdata->led_gpio);ret = devm_gpio_request(dev,gpio,"led_gpio");if(ret){printk("Failed to get led_gpio gpio.\n");return -1;}}gpio = of_get_named_gpio_flags(node, "smoke_sensor_gpio", 0, &flags);if (gpio_is_valid(gpio)){pdata->smoke_sensor_gpio        = gpio;printk(KERN_ERR"smoke_sensor_gpio: %d\n", pdata->smoke_sensor_gpio);ret = devm_gpio_request(dev,gpio, "smoke_sensor_gpio");if (ret) {printk("Failed to get smoke_sensor_gpio gpio.\n");return -1;}ret = gpio_direction_input(gpio);if (ret) {printk("Failed to set flame_sensor_gpio gpio.\n");return -1;}}return 0;}static void gpio_set_default(struct gpio_dev *pdata) {if (pdata->led_gpio) {gpio_direction_output(pdata->led_gpio, pdata->led_gpio_output);}
}int leds_probe(struct platform_device *pdev)
{int  ret = 0;printk(KERN_ALERT "%s \n",__func__);      gpio_dev_pointer = kmalloc(sizeof(struct gpio_dev), GFP_KERNEL);//为结构体指针申请空间if (gpio_dev_pointer == NULL) {printk(KERN_ERR"kmalloc struct gpio_dev err \n");return -ENOMEM;}memset(gpio_dev_pointer, 0, sizeof(struct gpio_dev)); //初始化结构体gpio_dev_pointer->pdev = pdev;ret = get_OF_node_property(gpio_dev_pointer);if(ret<0){printk(KERN_ERR"gpio_dt err \n");	return -1;}gpio_set_default(gpio_dev_pointer);ret = gpio_init_sysfs(&gpio_dev_pointer->pdev->dev);if(ret<0){printk(KERN_ERR"gpio_init_sysfs  err \n");	return -1;}printk(KERN_ALERT "%s  ok !!\n",__func__);return 0;}int leds_remove(struct platform_device *pdev)
{   gpio_remove_sysfs(&gpio_dev_pointer->pdev->dev);kfree(gpio_dev_pointer);printk("leds_remove ok\n");   return 0;
}static const struct of_device_id of_led_match[] = {{ .compatible = "sys_rw_led_sensor", },{},
};MODULE_DEVICE_TABLE(of, of_led_match);struct platform_driver leds_drv = {.driver = {.owner = THIS_MODULE,.name = "sys_rw_led driver" ,.of_match_table = of_led_match,},.probe = leds_probe,.remove = leds_remove,    
};
module_platform_driver(leds_drv);
MODULE_LICENSE("GPL");

3、测试代码

$ insmod gpio.ko
$ cd /sys/devices/sys_rw_gpio
$ echo 0 > led_gpio  //关灯
$ echo 1 > led_gpio  //亮灯	
$ cat smoke_sensor_gpio  //读管脚输入电平，默认读到0，用杜邦线，把它接到前面亮灯的管脚时，能成功读到1