android中device_attr 设备属性节点 以备后用

1. 在sys下创建一个节点

 static ssize_t gsensor_vendor_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
 {
     char  val;
     //val = simple_strtoul(buf, NULL, 10);
     sscanf(buf, "%d", &val);
     if(val == 0)
     {
         gpio_set_value(MMA8452_CON_PIN, 0);
     }
     else
     {
         gpio_set_value(MMA8452_CON_PIN, 1);
     }
     return strlen(buf);
 }

 static DEVICE_ATTR(vendor, 0777, gsensor_vendor_show, gsensor_vendor_store);

 static struct kobject *android_gsensor_kobj;

 static int gsensor_sysfs_init(void)
 {
     int ret ;

     android_gsensor_kobj = kobject_create_and_add("android_gsensor", NULL);
     if (android_gsensor_kobj == NULL) {
         mmaprintk(KERN_ERR
                "MMA8452 gsensor_sysfs_init:"\
                "subsystem_register failed\n");
         ret = -ENOMEM;
         goto err;
     }

     ret = sysfs_create_file(android_gsensor_kobj, &dev_attr_vendor.attr);   // "vendor"
     if (ret) {
         mmaprintk(KERN_ERR
                "MMA8452 gsensor_sysfs_init:"\
                "sysfs_create_group failed\n");
         goto err4;
     }

     return 0 ;
 err4:
     kobject_del(android_gsensor_kobj);
 err:
     return ret ;
 }

2.创建一个设备节点

 ssize_t led_3g_green_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
 {
     u8 val;
     val = simple_strtoul(buf, NULL, 10);
     if(val == 0){
         gpio_set_value(MX53_HMS_3G_LED_GREEN_EN, 0);
     }else{
         gpio_set_value(MX53_HMS_3G_LED_GREEN_EN, 1);
     }
     return count;
 }

 ssize_t led_3g_green_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
     sprintf(buf, "%d\n", gpio_get_value(MX53_HMS_3G_LED_GREEN_EN));
     return strlen(buf);
 }

 ssize_t led_3g_amber_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
 {
     u8 val;
     val = simple_strtoul(buf, NULL, 10);
     if(val == 0){
         gpio_set_value(MX53_HMS_3G_LED_AMBER_EN, 0);
     }else{
         gpio_set_value(MX53_HMS_3G_LED_AMBER_EN, 1);
     }
     return count;
 }

 ssize_t led_3g_amber_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
     sprintf(buf, "%d\n", gpio_get_value(MX53_HMS_3G_LED_AMBER_EN));
     return strlen(buf);
 }

 static DEVICE_ATTR(led_3g_green, S_IRUGO|S_IWUSR, led_3g_green_show, led_3g_green_store);
 static DEVICE_ATTR(led_3g_amber, S_IRUGO|S_IWUSR, led_3g_amber_show, led_3g_amber_store);

 static struct attribute* leds_mxc_gpio_attrs[] =
 {
     &dev_attr_led_3g_green.attr,
     &dev_attr_led_3g_amber.attr,
     NULL
 };

 static const struct attribute_group leds_mxc_gpio_group =
 {
     .attrs = leds_mxc_gpio_attrs,
 };


 result = sysfs_create_group(&drv_data->pdev->dev.kobj, &leds_mxc_gpio_group);
     if (result) {
         dev_err(&pdev->dev, "Create device file failed! ERRNO: %d\n",result);
         goto free_drv_data;
     }

以上两种方法创建的节点，通过串口，能够进行读写的操作。