基于DragonBoard 410c的环境光检测（二）

最新推荐文章于 2022-05-04 09:57:48 发布

原创最新推荐文章于 2022-05-04 09:57:48 发布 · 505 阅读

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CC 4.0 BY-SA版权

本文介绍了一种基于DragonBoard 410c开发板的光照传感器驱动程序的设计与实现过程。主要内容包括在设备树中配置传感器参数，编写并编译驱动程序代码，以及如何通过ADB命令读取光照强度值。

在http://blog.youkuaiyun.com/weixin_40109283/article/details/79035119博客中，已经介绍了该系统的硬件设计. 现在我们来谈谈软件部分的实现步骤和方法.

首先我们得先在设备树中配置相关的硬件信息，在apq8016-sbc.dtsi文件中做如下修改：

i2c@78b6000 { /* BLSP1 QUP2 */

light_sensor@29 {

compatible = "thunder,light_sensor";

reg = <0x29>;

};

然后编写相应的驱动程序，代码如下所示：

#include <linux/module.h>

#include <linux/delay.h>

#include <linux/i2c.h>

#include <linux/io.h>

#include <linux/platform_device.h>

#include <linux/async.h>

#include <linux/proc_fs.h>

#include <linux/fs.h>

#include <linux/cdev.h>

#include <linux/init.h>

#include <linux/slab.h>

#include <linux/mutex.h>

#include <linux/hwmon-sysfs.h>

#include <linux/err.h>

#include <linux/hwmon.h>

#include <linux/miscdevice.h>

#include <linux/poll.h>

#include <linux/gpio.h>

#include <linux/i2c/twl.h>

#include <linux/device.h>

#define MY_I2C_NAME "light_sensor"

struct light_sensor_data {

struct cdev dev;

struct i2c_client *client;

struct mutex update_lock;

};

static int light_sensor_get_adc_value(struct i2c_client *client, u8 cmd)

{

int ret;

ret = i2c_smbus_read_byte_data(client, cmd);

if (ret < 0)

return ret;

}

static ssize_t __light_sensor_show(struct i2c_client *client, char *buf)

{

int ret;

u8 ch0, ch1;

ret = i2c_smbus_write_byte_data(client, 0x80, 0x03);

if (ret < 0)

return ret;

ret = i2c_smbus_write_byte_data(client, 0x81, 0x01);

if (ret < 0)

return ret;

msleep(10);

ret = light_sensor_get_adc_value(client, 0x8c);

if (ret < 0)

return ret;

ch0 = ret;

printk(KERN_INFO "light_sensor_ch0 = %d lx\n", ch0);

ret = light_sensor_get_adc_value(client, 0x8d);

if (ret < 0)

return ret;

ch1 = ret;

printk(KERN_INFO "light_sensor_ch1 = %d lx\n", ch1);

/* Do the job */

ret = ch1 * 256 + ch0;

if (ret < 0)

return ret;

printk(KERN_INFO "light_sensor_ret = %d lx\n", ret);

return sprintf(buf, "%d\n", ret);

}

static ssize_t light_sensor_show_lux(struct device *dev,

struct device_attribute *attr, char *buf)

{

struct i2c_client *client = to_i2c_client(dev);

int ret;

ret = __light_sensor_show(client, buf);

if (ret < 0)

printk(KERN_INFO "light_sensor show failed\n");

return ret;

}

static DEVICE_ATTR(light_sensor, 0666,light_sensor_show_lux, NULL);

static struct attribute *light_sensor_attributes[] = {

&dev_attr_light_sensor.attr,

NULL

};

static const struct attribute_group light_sensor_attr_group = {

.attrs = light_sensor_attributes,

};

static int light_sensor_i2c_probe(struct i2c_client *client,

const struct i2c_device_id *id)

{

int result;

int err;

struct light_sensor_data *pdata;

struct i2c_adapter *adapter;

printk(KERN_INFO "light_sensor_i2c_probe enter\n");

adapter = to_i2c_adapter(client->dev.parent);

result = i2c_check_functionality(adapter,

I2C_FUNC_SMBUS_BYTE |

I2C_FUNC_SMBUS_BYTE_DATA);

if (!result)

goto err_out;

pdata = kzalloc(sizeof(struct light_sensor_data), GFP_KERNEL);

if (!pdata) {

result = -ENOMEM;

dev_err(&client->dev, "alloc data memory error!\n");

goto err_out;

}

pdata->client = client;

i2c_set_clientdata(client, pdata);

err = sysfs_create_group(&client->dev.kobj, &light_sensor_attr_group);

if (err)

goto err_out;

err_out:

return result;

err_out:

return result;

}

static int light_sensor_i2c_remove(struct i2c_client *client)

{

struct light_sensor_data *pdata = i2c_get_clientdata(client);

if(!pdata)

return 0;

sysfs_remove_group(&client->dev.kobj, &light_sensor_attr_group);

kfree(pdata);

return 0;

}

static const struct i2c_device_id light_sensor_i2c_id[] = {

{MY_I2C_NAME, 0},

{ }

};

MODULE_DEVICE_TABLE(i2c, light_sensor_i2c_id);

static const struct of_device_id of_light_sensor_match[] = {

{.compatible = "thunder,light_sensor", },

{},

};

static struct i2c_driver light_sensor_i2c_driver = {

.driver = {

.owner = THIS_MODULE,

.name = "light_sensor",

.of_match_table = of_light_sensor_match,

.probe = light_sensor_i2c_probe,

.remove = light_sensor_i2c_remove,

.id_table = light_sensor_i2c_id,

};

module_i2c_driver(light_sensor_i2c_driver);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("heql0703@thundersoft.com");

将代码编译后烧写到DragonBoard 410c开发板后启动开发板，用adb命令进入开发板用cat命令查看对应生成的节点light_sensor_lux，就可以看到光照强度的值了.