在平常做一些驱动调试的时候，每次都写应用去调试相对较麻烦，有一个非常便捷的操作方法就是使用device_attr，只需要执行shell指令例如echo和cat就可以看到效果，不需要再单独写一个测试demo。
看网上很多博客在这一块的使用上写的都有些复杂了，都是纯写一个用DEVICE_ATTR的demo，很少结合具体驱动来配合，完成调试工作，所以决定自己也写一篇。
1.函数介绍
1.1 DEVICE_ATTR
DEVICE_ATTR宏定义在kernel/include/linux/device.h文件中。原型如下：
#define DEVICE_ATTR(_name, _mode, _show, _store) \struct device_attribute dev_attr_##_name = __ATTR(_name, _mode, _show, _store)
作用：定义一个device_attribute结构体，之后device_create_file使用。
_name：名称，在/sys/device/virtual中的名称，##name代表将name的字段直接替换到##_name处，所以假设_name为ap3216c_test，那这边定义的结构体名就是dev_attr_ap3216c_test
_mode：访问权限，与普通文件相同，可以使用0644也可以使用S_IWUSR|S_IRUSR这种格式代表用户可读可写
_show：显示函数，cat文件时调用此函数
_store：写函数，echo内容到文件时调用此函数
1.2 device_create_file
int device_create_file(struct device *dev, const struct device_attribute *attr)
{int error = 0;if (dev)error = sysfs_create_file(&dev->kobj, &attr->attr);return error;
}
作用：创建device属性文件
dev：设备指针，通过device_create创建
attr：device_attribute指针，就是通过DEVICE_ATTR宏生成的dev_attr_name指针
1.3 device_remove_file
void device_remove_file(struct device *dev, const struct device_attribute *attr)
{if (dev)sysfs_remove_file(&dev->kobj, &attr->attr);
}
作用：删除device属性文件
2.例程
这里我是结合了一个I2C设备驱动，对这个I2C驱动实现感兴趣的话可以看我另外一篇博客:I2C驱动编写
完成这个驱动后，之后便可以使用cat和echo来进行测试，而不再需要编写应用的测试demo。
使用主要分为四步：
1）使用DEVICE_ATTR宏实现结构体
static DEVICE_ATTR(ap3216c_test, S_IWUSR|S_IRUSR, ap3216c_show, ap3216c_store);
2）实现show和store的函数
static ssize_t ap3216c_show(struct device *dev, struct device_attribute *attr,char *buf)
{u8 data[3] = {0};printk("ap3216c ap3216c_show");__ap3216c_read(&ap3216c_dev, data);memcpy(buf, data, sizeof(data) / sizeof(data[0]));return sizeof(data) / sizeof(data[0]);
}static ssize_t ap3216c_store(struct device *dev,struct device_attribute *attr,const char *buf, size_t count)
{printk("ap3216c ap3216c_store, buf:%s, len:%d", buf, count);return count;
}
3）调用device_create_file创建device属性文件
if (device_create_file(ap3216c_dev.m_dev, &dev_attr_ap3216c_test) != 0) {printk("ap3216c device create failed\n");return -1;
}
4）驱动卸载时调用device_delete_file删除device属性文件
device_remove_file(ap3216c_dev.m_cdev, &dev_attr_ap3216c_test);
完整代码如下：
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of_gpio.h>
#include <linux/semaphore.h>
#include <linux/timer.h>
#include <linux/i2c.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>#include <linux/device.h>/* AP3316C 寄存器 */
#define AP3216C_SYSTEMCONG 0x00 /* 配置寄存器 */
#define AP3216C_INTSTATUS 0X01 /* 中断状态寄存器 */
#define AP3216C_INTCLEAR 0X02 /* 中断清除寄存器 */
#define AP3216C_IRDATALOW 0x0A /* IR 数据低字节 */
#define AP3216C_IRDATAHIGH 0x0B /* IR 数据高字节 */
#define AP3216C_ALSDATALOW 0x0C /* ALS 数据低字节 */
#define AP3216C_ALSDATAHIGH 0X0D /* ALS 数据高字节 */
#define AP3216C_PSDATALOW 0X0E /* PS 数据低字节 */
#define AP3216C_PSDATAHIGH 0X0F /* PS 数据高字节 */#define AP3216C_DATA_REG_NUM 6#define AP3216C_NAME "ap3216c"struct ap3216c_dev_t {dev_t m_devid;struct cdev m_cdev; ///< 字符设备结构struct class *m_class; ///< 类struct device *m_dev; ///< 设备struct device_node *nd; ///< 设备节点int devid; ///< 设备号int major; ///< 主设备号struct i2c_client* client; ///<i2c设备
};struct ap3216c_dev_t ap3216c_dev = {0}; static ssize_t __ap3216c_read(struct ap3216c_dev_t *dev, char __user *data);static ssize_t ap3216c_show(struct device *dev, struct device_attribute *attr,char *buf)
{u8 data[3] = {0};printk("ap3216c ap3216c_show");__ap3216c_read(&ap3216c_dev, data);memcpy(buf, data, sizeof(data) / sizeof(data[0]));return sizeof(data) / sizeof(data[0]);
}static ssize_t ap3216c_store(struct device *dev,struct device_attribute *attr,const char *buf, size_t count)
{printk("ap3216c ap3216c_store, buf:%s, len:%d", buf, count);return count;
}static DEVICE_ATTR(ap3216c_test, S_IWUSR|S_IRUSR, ap3216c_show, ap3216c_store);static int ap3216c_write_reg(struct ap3216c_dev_t *dev, u8 reg, u8 *data, u16 len)
{struct i2c_client* client = (struct i2c_client*)dev->client;struct i2c_msg msg;msg.addr = client->addr; ///< 设备地址msg.flags = 0; ///< 写数据msg.buf[0] = reg; ///< 操作寄存器地址memcpy(&msg.buf[1], data, len); ///< 写寄存器的数据msg.len = len + 1 ; ///< 1byte寄存器地址+data的长度 return i2c_transfer(client->adapter, &msg, 1);
}static int ap3216c_read_reg(struct ap3216c_dev_t *dev, u8 reg, u8 *data, u16 len)
{struct i2c_client* client = (struct i2c_client*)dev->client;struct i2c_msg msg[2];msg[0].addr = client->addr; ///< 设备地址msg[0].flags = 0; ///< 写数据msg[0].buf = ® ///< 操作寄存器地址msg[0].len = 1 ; ///< 1byte寄存器地址 msg[1].addr = client->addr; ///< 设备地址msg[1].flags = I2C_M_RD; ///< 读数据msg[1].buf = data; ///< 读取数据缓冲区msg[1].len = len; ///< 读取数据长度 return i2c_transfer(client->adapter, &msg, 2);
}static int ap3216c_open(struct inode *node, struct file *file)
{u8 value = 0x00;printk("ap3216c driver open\n");file->private_data = (void *)&ap3216c_dev; ///< 设置私有数据ap3216c_write_reg(file->private_data, AP3216C_SYSTEMCONG, &value, 1); ///< set sw resetmdelay(20); ///< 最少等待10msvalue = 0x03;ap3216c_write_reg(file->private_data, AP3216C_SYSTEMCONG, &value, 1); ///< 设置为ALS and PS+IR模式printk("ap3216c driver open success\n");return 0;
}static int ap3216c_close(struct inode *node, struct file *file)
{u8 value = 0x00;printk("ap3216c driver close\n");file->private_data = (void *)&ap3216c_dev; ///< 设置私有数据ap3216c_write_reg(file->private_data, AP3216C_SYSTEMCONG, &value, 1); ///< set sw resetprintk("ap3216c driver close success\n");return 0;
}static ssize_t __ap3216c_read(struct ap3216c_dev_t *dev, char __user *data)
{int i = 0;int ret = 0;u8 read_buf[AP3216C_DATA_REG_NUM] = {0};/// 循环将IR、ALS、PS中的寄存器数据读取for (i = 0; i < AP3216C_DATA_REG_NUM; i++) {ret = ap3216c_read_reg(dev, AP3216C_IRDATALOW + i, read_buf, 6);printk("ap3216c driver read ret:%d, reg:%x, value:%d\n", ret, AP3216C_IRDATALOW + i, read_buf[i]);}if (read_buf[0] & 0x80) {data[0] = 0;printk("ap3216c driver read ir data error\n");} else {data[0] = (read_buf[1] << 2) | read_buf[0];printk("ap3216c driver read ir data success, data:%x\n", data[0]);}data[1] = (read_buf[3] << 8) | read_buf[2];printk("ap3216c driver read als data success, data:%x\n", data[1]);if (read_buf[4] & 0x80) {data[2] = 0;printk("ap3216c driver read ps data error\n");} else {data[2] = ((read_buf[5] & 0x3f) << 4) | (read_buf[4] & 0x0f);printk("ap3216c driver read ir data success, data:%x\n", data[0]);}printk("ap3216c driver read als data success, data:%x\n", data[1]);return 0;
}static ssize_t ap3216c_read(struct file *file, char __user *buf, size_t cnt, loff_t *off)
{u8 data[3] = {0};int ret = 0;printk("ap3216c driver read\n");file->private_data = (void *)&ap3216c_dev; ///< 设置私有数据__ap3216c_read(file->private_data, data);if (copy_to_user(buf, data, sizeof(data) / sizeof(data[0])) != 0) {return -1;}printk("ap3216c driver read sucess, ret:%d\n", ret);return ret;
}static struct file_operations ap3216c_fops = {.owner = THIS_MODULE,.open = ap3216c_open,.release = ap3216c_close,.read = ap3216c_read,
};int ap3216c_probe(struct i2c_client *client, const struct i2c_device_id *id)
{printk("ap3216c driver probe begin\n");///1.申请设备号if (ap3216c_dev.major) {ap3216c_dev.devid = MKDEV(ap3216c_dev.major, 0);register_chrdev_region(ap3216c_dev.devid, 1, AP3216C_NAME);} else {alloc_chrdev_region(&ap3216c_dev.devid, 0, 1, AP3216C_NAME);ap3216c_dev.major = MAJOR(ap3216c_dev.devid);}///2.cdev_init、cdev_addcdev_init(&ap3216c_dev.m_cdev, &ap3216c_fops);cdev_add(&ap3216c_dev.m_cdev, ap3216c_dev.devid, 1);///3.class_createap3216c_dev.m_class = class_create(THIS_MODULE, AP3216C_NAME);if (IS_ERR(ap3216c_dev.m_class)) {return PTR_ERR(ap3216c_dev.m_class);}///4.device_create ap3216c_dev.m_dev = device_create(ap3216c_dev.m_class, NULL, ap3216c_dev.devid, NULL, AP3216C_NAME);if (IS_ERR(ap3216c_dev.m_dev)) {return PTR_ERR(ap3216c_dev.m_dev);}/// for debug:if (device_create_file(ap3216c_dev.m_dev, &dev_attr_ap3216c_test) != 0) {printk("ap3216c device create failed\n");return -1;}ap3216c_dev.client = client;printk("ap3216c driver probe done\n");return 0;
}int ap3216c_remove(struct i2c_client *client)
{printk("ap3216c driver remove begin\n");///cdev_delcdev_del(&ap3216c_dev.m_cdev);///注销设备号unregister_chrdev(ap3216c_dev.devid, AP3216C_NAME);///device_destroydevice_destroy(ap3216c_dev.m_class, ap3216c_dev.devid);///class_desroyclass_destroy(ap3216c_dev.m_class);printk("ap3216c driver remove done\n");return 0;
}/// 传统方式匹配
static const struct i2c_device_id ap3216c_id[] = {{"alientek,ap3216c", 0}, {}
};/// 设备树方式匹配
static const struct of_device_id ap3216c_of_match[] = {{.compatible = "alientek,ap3216c"}
};static struct i2c_driver ap3216c_driver = {.probe = ap3216c_probe,.remove = ap3216c_remove,.driver = {.owner = THIS_MODULE,.name = "ap3216c",.of_match_table = ap3216c_of_match,},.id_table = ap3216c_id,
};static int __init ap3216c_init(void)
{int ret = 0;printk("ap3216c driver init begin\n");ret = i2c_add_driver(&ap3216c_driver);printk("ap3216c driver init done, ret:%d\n", ret);return ret;
}static int __exit ap3216c_exit(void)
{printk("ap3216c driver exit begin\n"); i2c_del_driver(&ap3216c_driver);printk("ap3216c driver exit done\n"); return 0;
}module_init(ap3216c_init);
module_exit(ap3216c_exit);MODULE_LICENSE("GPL");
MODULE_AUTHOR("xuzhangxin");
3.测试效果
