Android 系統開發時有些資料需要同步到上層應用進行UI顯示，如果是定製功能且資料量不大，可以考慮通過檔案節點方式在應用和驅動之間進行通訊。

　　以下介紹兩種檔案節點的新增方法：

一、/proc/節點：

include <linux/uaccess.h>

include <linux/proc_fs.h>

include <linux/module.h>

include <linux/kernel.h>

include <linux/delay.h>

include <asm/uaccess.h>

include <linux/sched.h>

include <linux/init.h>

include <asm/irq.h>

include <asm/io.h>

define MSG_BUF_LEN 1024

static unsigned char msg_buf[MSG_BUF_LEN] = {0};
static unsigned int msg_len = 0;
static DECLARE_WAIT_QUEUE_HEAD(upgrade_percentage_waitq);

uint8_t upgrade_percentage = 0;
//讀介面
static ssize_t upgrade_percentage_read(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
unsigned int ret = 0;

// 如果 msg_len 為 0，則等待資料
wait_event_interruptible(upgrade_percentage_waitq, msg_len);
copy_to_user(user_buf, msg_buf, msg_len);
ret = msg_len;
msg_len = 0;

printk("upgrade_percentage(r) : %d \n", upgrade_percentage);

return ret;

}
//寫介面
static ssize_t upgrade_percentage_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
if(copy_from_user(msg_buf, user_buf, count)) {
return -EFAULT;
}
msg_len = count;
wake_up_interruptible(&upgrade_percentage_waitq);
return count;
}

const struct file_operations upgrade_percentage_operations = {
.read = upgrade_percentage_read,
.write = upgrade_percentage_write,
};

static int nti2c_init(void)
{
int ret;

// -> "/proc/nt68411/upgrade_percentage"
printk("proc_create upgrade_percentage ... \n");    proc_mkdir("nt68411", NULL);    proc_create("upgrade_percentage", S_IRUSR, NULL, &upgrade_percentage_operations);

　　return ret;
}

static void nti2c_exit(void)
{
remove_proc_entry("nt68411/upgrade_percentage", NULL);
printk("%s, ok! \n", func);
}

module_init(nti2c_init);
module_exit(nti2c_exit);

MODULE_AUTHOR("Sheldon");
MODULE_DESCRIPTION("driver for linux platform");
MODULE_LICENSE("GPL");

二、/sys/class/ 節點：

include <linux/module.h>

include <linux/moduleparam.h>

include <linux/mod_devicetable.h>

include <linux/device.h>

include <linux/platform_device.h>

include <linux/init.h>

include <linux/fs.h>

include <linux/string.h>

include <asm/uaccess.h>

include <linux/delay.h>

include <linux/of.h>

include <linux/io.h>

include <linux/gpio.h>

include <linux/of_gpio.h>

include <linux/vmalloc.h>

include <linux/uaccess.h>

include <linux/proc_fs.h>

include <linux/kernel.h>

include <linux/sched.h>

include <asm/irq.h>

include <asm/io.h>

static struct class *driver_class = NULL;
static struct device *driver_dev = NULL;

static ssize_t driver_percentage_show(struct device *dev, struct device_attribute *attr, char *buf)
{
printk("NT68411 upgrade_percentage : %d \n", upgrade_percentage);
return sprintf(buf,"%u\n",upgrade_percentage);
}

static ssize_t driver_percentage_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t size)
{
int value = simple_strtoul(buf, NULL, 0);
printk("NT68411 driver_percentage_store : %d \n", value);
return size;
}

static struct device_attribute dev_nt68411_upgrade_attr = {
.attr = {
.name = "percentage",
.mode = 0666,
},
.show = driver_percentage_show,
.store = driver_percentage_store,
};

static int nti2c_init(void)
{
printk("%s, Enter \n", func);
　　 // --> /sys/class/nt68411/upgrade/percentage
driver_class = class_create(THIS_MODULE, "nt68411");
if (IS_ERR(driver_class)) {
printk("nt68411 class_create fail\n");
}

driver_dev = device_create(driver_class, NULL, 0, 0,"upgrade");
if(NULL == driver_dev){
    printk("nt68411 device_create fail\n");
}
device_create_file(driver_dev, &dev_nt68411_upgrade_attr);

printk("%s, Exit \n", __func__);
return 0;

}

static void nti2c_exit(void)
{
device_remove_file(driver_dev, &dev_nt68411_upgrade_attr);
device_unregister(driver_dev);
if(driver_class!=NULL)
class_destroy(driver_class);

printk("%s, ok! \n", __func__);

}

module_init(nti2c_init);
module_exit(nti2c_exit);

MODULE_AUTHOR("Sheldon");
MODULE_DESCRIPTION("driver for linux platform");
MODULE_LICENSE("GPL");

Android : kernel中新增虛擬檔案節點

include <linux/uaccess.h>

include <linux/proc_fs.h>

include <linux/module.h>

include <linux/kernel.h>

include <linux/delay.h>

include <asm/uaccess.h>

include <linux/sched.h>

include <linux/init.h>

include <asm/irq.h>

include <asm/io.h>

define MSG_BUF_LEN 1024

include <linux/module.h>

include <linux/moduleparam.h>

include <linux/mod_devicetable.h>

include <linux/device.h>

include <linux/platform_device.h>

include <linux/init.h>

include <linux/fs.h>

include <linux/string.h>

include <asm/uaccess.h>

include <linux/delay.h>

include <linux/of.h>

include <linux/io.h>

include <linux/gpio.h>

include <linux/of_gpio.h>

include <linux/vmalloc.h>

include <linux/uaccess.h>

include <linux/proc_fs.h>

include <linux/kernel.h>

include <linux/sched.h>

include <asm/irq.h>

include <asm/io.h>

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