/* drivers/misc/akm8975.c - akm8975 compass driver
#include <linux/interrupt.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/irq.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <linux/uaccess.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/workqueue.h>
#include <linux/freezer.h>
#include <linux/akm8975.h>
#include <linux/earlysuspend.h>
#define AK8975DRV_CALL_DBG 0 调试开关
#if AK8975DRV_CALL_DBG
#define FUNCDBG(msg) pr_err("%s:%s\n", __func__, msg);
#else
#define FUNCDBG(msg)
#endif
#define AK8975DRV_DATA_DBG 0
#define MAX_FAILURE_COUNT 10
struct akm8975_data {
struct i2c_client *this_client;
struct akm8975_platform_data *pdata;
struct input_dev *input_dev;
struct work_struct work;
struct mutex flags_lock;
#ifdef CONFIG_HAS_EARLYSUSPEND
struct early_suspend early_suspend;
#endif
};
/*
* Because misc devices can not carry a pointer from driver register to
* open, we keep this global. This limits the driver to a single instance.
*/
struct akm8975_data *akmd_data;
static DECLARE_WAIT_QUEUE_HEAD(open_wq);
static atomic_t open_flag;
static short m_flag;
static short a_flag;
static short t_flag;
static short mv_flag;
static short akmd_delay;
static ssize_t akm8975_show(struct device *dev, struct device_attribute *attr,//功能主要是将相关数据打印到内存当中。
char *buf)
{
struct i2c_client *client = to_i2c_client(dev);
return sprintf(buf, "%u\n", i2c_smbus_read_byte_data(client,
AK8975_REG_CNTL));//Operation mode setting
}
static ssize_t akm8975_store(struct device *dev, struct device_attribute *attr,//功能主要是获取buf中存在的控制值。
const char *buf, size_t count)
{
struct i2c_client *client = to_i2c_client(dev);
unsigned long val;
strict_strtoul(buf, 10, &val);
if (val > 0xff)
return -EINVAL;
i2c_smbus_write_byte_data(client, AK8975_REG_CNTL, val);//write Operation mode
return count;
}
static DEVICE_ATTR(akm_ms1, S_IWUSR | S_IRUGO, akm8975_show, akm8975_store);
/*sysfs属性的功能只能靠阅读源代码来理解。在内核中， sysfs属性一般是由 __ATTR
系列的宏来声明的，如对设备的使用 DEVICE_ATTR，对总线使用 BUS_ATTR，对驱动使用 DRIVER_ATTR
，对类别(class)使用 CLASS_ATTR,这四个高级的宏来自于 <include/linux/device.h>,都是以更低层的来自include/linux/sysfs.h>中的 __ATTR/__ATRR_RO
宏实现；因此我们在内核源码树中相应位置 drivers/scsi/ 找到这几个宏的使用情况，可以得到在 drivers/scsi/scsi_sysfs.c中。3.4填充设备属性DEVICE_ATTR
static DEVICE_ATTR(print, S_IWUSR | S_IRUGO,mmaxxxxx_show_print, mmaxxxxx_store_print);
其中有四个参数，分别表示是称、权限位、读函数、写函数。
3.5属性数组mmaxxxxx_attributes
主要是填充设备属性位置。
static
struct attribute *mmaxxxxx_attributes[] = {
&dev_attr_print.attr,
NULL
};
3.6将属性数组加到属性组（group）里。
static const struct attribute_group
mmaxxxxx_attr_group = {
.attrs
= mmaxxxxx_attributes,
};
至此完成了属性组的添加工作，通过adb连接去硬件系统中对应的文件为sys/devices/i2c-0/x-xxxx/print，x-xxxx对应的是芯片的地址线。
4 总结
文章中采用标准模块化得方法，调用内核函数，将i2c模块挂载到内核系统当中，并通过misc设备留接口给上层提供调用。在模块工作过程中，通过i2c读函数获取了实时的位置信息，并通过input设备将数据上报给用户层。
*/
static int akm8975_i2c_rxdata(struct akm8975_data *akm, char *buf, int length)
{
struct i2c_msg msgs[] = {
{
.addr = akm->this_client->addr，
.flags = 0, //没有就是写
.len = 1, //数据字节数
.buf = buf, //数据保存的地方
},
{
.addr = akm->this_client->addr,
.flags = I2C_M_RD, //读标记，没有就是写
.len = length, //数据字节数
.buf = buf, //数据保存的地方
},
};
FUNCDBG("called");
if (i2c_transfer(akm->this_client->adapter, msgs, 2) < 0) {
pr_err("akm8975_i2c_rxdata: transfer error\n");
return EIO;
} else
return 0;
}
static int akm8975_i2c_txdata(struct akm8975_data *akm, char *buf, int length)
{
struct i2c_msg msgs[] = {
{
.addr = akm->this_client->addr,
.flags = 0,
.len = length,
.buf = buf,
},
};
FUNCDBG("called");
if (i2c_transfer(akm->this_client->adapter, msgs, 1) < 0) {
pr_err("akm8975_i2c_txdata: transfer error\n");
return -EIO;
} else
return 0;
}
static void akm8975_ecs_report_value(struct akm8975_data *akm, short *rbuf)
{
struct akm8975_data *data = i2c_get_clientdata(akm->this_client);
FUNCDBG("called");
#if AK8975DRV_DATA_DBG 调试开关
pr_info("akm8975_ecs_report_value: yaw = %d, pitch = %d, roll = %d\n",
rbuf[0], rbuf[1], rbuf[2]);
pr_info("tmp = %d, m_stat= %d, g_stat=%d\n", rbuf[3], rbuf[4], rbuf[5]);
pr_info("Acceleration: x = %d LSB, y = %d LSB, z = %d LSB\n",
rbuf[6], rbuf[7], rbuf[8]);
pr_info("Magnetic: x = %d LSB, y = %d LSB, z = %d LSB\n\n",
rbuf[9], rbuf[10], rbuf[11]);
#endif
mutex_lock(&akm->flags_lock);
/* Report magnetic sensor information */
if (m_flag) {
input_report_abs(data->input_dev, ABS_RX, rbuf[0]);
input_report_abs(data->input_dev, ABS_RY, rbuf[1]);
input_report_abs(data->input_dev, ABS_RZ, rbuf[2]);
input_report_abs(data->input_dev, ABS_RUDDER, rbuf[4]);
}
/* Report acceleration sensor information */
if (a_flag) {
input_report_abs(data->input_dev, ABS_X, rbuf[6]);
input_report_abs(data->input_dev, ABS_Y, rbuf[7]);
input_report_abs(data->input_dev, ABS_Z, rbuf[8]);
input_report_abs(data->input_dev, ABS_WHEEL, rbuf[5]);
}
/* Report temperature information */
if (t_flag)
input_report_abs(data->input_dev, ABS_THROTTLE, rbuf[3]);
if (mv_flag) {
input_report_abs(data->input_dev, ABS_HAT0X, rbuf[9]);
input_report_abs(data->input_dev, ABS_HAT0Y, rbuf[10]);
input_report_abs(data->input_dev, ABS_BRAKE, rbuf[11]);
}
mutex_unlock(&akm->flags_lock);
input_sync(data->input_dev);
}
static void akm8975_ecs_close_done(struct akm8975_data *akm)
{
FUNCDBG("called");
mutex_lock(&akm->flags_lock);
m_flag = 1;
a_flag = 1;
t_flag = 1;
mv_flag = 1;
mutex_unlock(&akm->flags_lock);
}
static int akm_aot_open(struct inode *inode, struct file *file)
{
int ret = -1;
FUNCDBG("called");
if (atomic_cmpxchg(&open_flag, 0, 1) == 0) {
wake_up(&open_wq);
ret = 0;
}
ret = nonseekable_open(inode, file);
if (ret)
return ret;
file->private_data = akmd_data;
return ret;
}
static int akm_aot_release(struct inode *inode, struct file *file)
{
FUNCDBG("called");
atomic_set(&open_flag, 0);
wake_up(&open_wq);
return 0;
}
//akm_aot_ioctl,主要是获取和设置sensor状态（打开和关闭）和延时
static int akm_aot_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
void __user *argp = (void __user *) arg;
short flag;
struct akm8975_data *akm = file->private_data;
FUNCDBG("called");
switch (cmd) {
case ECS_IOCTL_APP_SET_MFLAG:
case ECS_IOCTL_APP_SET_AFLAG:
case ECS_IOCTL_APP_SET_MVFLAG:
if (copy_from_user(&flag, argp, sizeof(flag)))
return -EFAULT;
if (flag < 0 || flag > 1)
return -EINVAL;
break;
case ECS_IOCTL_APP_SET_DELAY:
if (copy_from_user(&flag, argp, sizeof(flag)))
return -EFAULT;
break;
default:
break;
}
mutex_lock(&akm->flags_lock);
switch (cmd) {
case ECS_IOCTL_APP_SET_MFLAG:
m_flag = flag;
break;
case ECS_IOCTL_APP_GET_MFLAG:
flag = m_flag;
break;
case ECS_IOCTL_APP_SET_AFLAG:
a_flag = flag;
break;
case ECS_IOCTL_APP_GET_AFLAG:
flag = a_flag;
break;
case ECS_IOCTL_APP_SET_MVFLAG:
mv_flag = flag;
break;
case ECS_IOCTL_APP_GET_MVFLAG:
flag = mv_flag;
break;
case ECS_IOCTL_APP_SET_DELAY:
akmd_delay = flag;
break;
case ECS_IOCTL_APP_GET_DELAY:
flag = akmd_delay;
break;
default:
return -ENOTTY;
}
mutex_unlock(&akm->flags_lock);
switch (cmd) {
case ECS_IOCTL_APP_GET_MFLAG:
case ECS_IOCTL_APP_GET_AFLAG:
case ECS_IOCTL_APP_GET_MVFLAG:
case ECS_IOCTL_APP_GET_DELAY:
if (copy_to_user(argp, &flag, sizeof(flag)))
return -EFAULT;
break;
default:
break;
}
return 0;
}
static int akmd_open(struct inode *inode, struct file *file)
{
int err = 0;
FUNCDBG("called");
err = nonseekable_open(inode, file);
if (err)
return err;
file->private_data = akmd_data;
return 0;
}
static int akmd_release(struct inode *inode, struct file *file)
{
struct akm8975_data *akm = file->private_data;
FUNCDBG("called");
akm8975_ecs_close_done(akm);
return 0;
}
//通过akmd_ioctl实现数据与内核层和externel层的写入和读取。
static int akmd_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
unsigned long arg)
{
void __user *argp = (void __user *) arg;
char rwbuf[16];
int ret = -1;
int status;
short value[12];
short delay;
struct akm8975_data *akm = file->private_data;
FUNCDBG("called");
switch (cmd) {
case ECS_IOCTL_READ:
case ECS_IOCTL_WRITE:
if (copy_from_user(&rwbuf, argp, sizeof(rwbuf)))
return -EFAULT;
break;
case ECS_IOCTL_SET_YPR:
if (copy_from_user(&value, argp, sizeof(value)))
return -EFAULT;
break;
default:
break;
}
switch (cmd) {
case ECS_IOCTL_READ:
if (rwbuf[0] < 1)
return -EINVAL;
ret = akm8975_i2c_rxdata(akm, &rwbuf[1], rwbuf[0]);
if (ret < 0)
return ret;
break;
case ECS_IOCTL_WRITE:
if (rwbuf[0] < 2)
return -EINVAL;
ret = akm8975_i2c_txdata(akm, &rwbuf[1], rwbuf[0]);
if (ret < 0)
return ret;
break;
case ECS_IOCTL_SET_YPR:
akm8975_ecs_report_value(akm, value);
break;
case ECS_IOCTL_GET_OPEN_STATUS:
wait_event_interruptible(open_wq,
(atomic_read(&open_flag) != 0));
status = atomic_read(&open_flag);
break;
case ECS_IOCTL_GET_CLOSE_STATUS:
wait_event_interruptible(open_wq,
(atomic_read(&open_flag) == 0));
status = atomic_read(&open_flag);
break;
case ECS_IOCTL_GET_DELAY:
delay = akmd_delay;
break;
default:
FUNCDBG("Unknown cmd\n");
return -ENOTTY;
}
switch (cmd) {
case ECS_IOCTL_READ:
if (copy_to_user(argp, &rwbuf, sizeof(rwbuf)))
return -EFAULT;
break;
case ECS_IOCTL_GET_OPEN_STATUS:
case ECS_IOCTL_GET_CLOSE_STATUS:
if (copy_to_user(argp, &status, sizeof(status)))
return -EFAULT;
break;
case ECS_IOCTL_GET_DELAY:
if (copy_to_user(argp, &delay, sizeof(delay)))
return -EFAULT;
break;
default:
break;
}
return 0;
}
/* needed to clear the int. pin */
static void akm_work_func(struct work_struct *work)
{
struct akm8975_data *akm =
container_of(work, struct akm8975_data, work);
FUNCDBG("called");
enable_irq(akm->this_client->irq);
}
static irqreturn_t akm8975_interrupt(int irq, void *dev_id)
{
struct akm8975_data *akm = dev_id;
FUNCDBG("called");
disable_irq_nosync(akm->this_client->irq);
schedule_work(&akm->work);
return IRQ_HANDLED;
}
static int akm8975_power_off(struct akm8975_data *akm)
{
#if AK8975DRV_CALL_DBG
pr_info("%s\n", __func__);
#endif
if (akm->pdata->power_off)
akm->pdata->power_off();
return 0;
}
static int akm8975_power_on(struct akm8975_data *akm)
{
int err;
#if AK8975DRV_CALL_DBG
pr_info("%s power_on \n", __func__);
#endif
if (akm->pdata->power_on) {
err = akm->pdata->power_on();
if (err < 0)
return err;
}
return 0;
}
static int akm8975_suspend(struct i2c_client *client, pm_message_t mesg)
{
struct akm8975_data *akm = i2c_get_clientdata(client);
#if AK8975DRV_CALL_DBG
pr_info("%s\n", __func__);
#endif
/* TO DO: might need more work after power mgmt
is enabled */
return akm8975_power_off(akm);
}
static int akm8975_resume(struct i2c_client *client)
{
struct akm8975_data *akm = i2c_get_clientdata(client);
#if AK8975DRV_CALL_DBG
pr_info("%s\n", __func__);
#endif
/* TO DO: might need more work after power mgmt
is enabled */
return akm8975_power_on(akm);
}
#ifdef CONFIG_HAS_EARLYSUSPEND
static void akm8975_early_suspend(struct early_suspend *handler)
{
struct akm8975_data *akm;
akm = container_of(handler, struct akm8975_data, early_suspend);
#if AK8975DRV_CALL_DBG
pr_info("%s\n", __func__);
#endif
akm8975_suspend(akm->this_client, PMSG_SUSPEND);
}
static void akm8975_early_resume(struct early_suspend *handler)
{
struct akm8975_data *akm;
akm = container_of(handler, struct akm8975_data, early_suspend);
#if AK8975DRV_CALL_DBG
pr_info("%s\n", __func__);
#endif
akm8975_resume(akm->this_client);
}
#endif
static int akm8975_init_client(struct i2c_client *client)
{
struct akm8975_data *data;
int ret;
data = i2c_get_clientdata(client);
ret = request_irq(client->irq, akm8975_interrupt, IRQF_TRIGGER_RISING,
"akm8975", data);
if (ret < 0) {
pr_err("akm8975_init_client: request irq failed\n");
goto err;
}
init_waitqueue_head(&open_wq);
mutex_lock(&data->flags_lock);
m_flag = 1;
a_flag = 1;
t_flag = 1;
mv_flag = 1;
mutex_unlock(&data->flags_lock);
return 0;
err:
return ret;
}
static const struct file_operations akmd_fops = {
.owner = THIS_MODULE,
.open = akmd_open,
.release = akmd_release,
.ioctl = akmd_ioctl,
};
static const struct file_operations akm_aot_fops = {
.owner = THIS_MODULE,
.open = akm_aot_open,
.release = akm_aot_release,
.ioctl = akm_aot_ioctl,
};
static struct miscdevice akm_aot_device = {
.minor = MISC_DYNAMIC_MINOR,
.name = "akm8975_aot",
.fops = &akm_aot_fops,
};
static struct miscdevice akmd_device = {
.minor = MISC_DYNAMIC_MINOR,
.name = "akm8975_dev",
.fops = &akmd_fops,
};
int akm8975_probe(struct i2c_client *client,
const struct i2c_device_id *devid)
{
struct akm8975_data *akm;
int err;
FUNCDBG("called");
if (client->dev.platform_data == NULL) {
dev_err(&client->dev, "platform data is NULL. exiting.\n");
err = -ENODEV;
goto exit_platform_data_null;
}
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
dev_err(&client->dev, "platform data is NULL. exiting.\n");
err = -ENODEV;
goto exit_check_functionality_failed;
}
akm = kzalloc(sizeof(struct akm8975_data), GFP_KERNEL);
if (!akm) {
dev_err(&client->dev,
"failed to allocate memory for module data\n");
err = -ENOMEM;
goto exit_alloc_data_failed;
}
akm->pdata = client->dev.platform_data;
mutex_init(&akm->flags_lock);
INIT_WORK(&akm->work, akm_work_func);/*INIT_WORK(_work, _func, _data)创建一个workqueue来处理中断*/
i2c_set_clientdata(client, akm);
err = akm8975_power_on(akm);
if (err < 0)
goto exit_power_on_failed;
akm8975_init_client(client);
akm->this_client = client;
akmd_data = akm;
akm->input_dev = input_allocate_device();
if (!akm->input_dev) {
err = -ENOMEM;
dev_err(&akm->this_client->dev,
"input device allocate failed\n");
goto exit_input_dev_alloc_failed;
}
set_bit(EV_ABS, akm->input_dev->evbit);
/* yaw */
input_set_abs_params(akm->input_dev, ABS_RX, 0, 23040, 0, 0);
/* pitch */
input_set_abs_params(akm->input_dev, ABS_RY, -11520, 11520, 0, 0);
/* roll */
input_set_abs_params(akm->input_dev, ABS_RZ, -5760, 5760, 0, 0);
/* x-axis acceleration */
input_set_abs_params(akm->input_dev, ABS_X, -5760, 5760, 0, 0);
/* y-axis acceleration */
input_set_abs_params(akm->input_dev, ABS_Y, -5760, 5760, 0, 0);
/* z-axis acceleration */
input_set_abs_params(akm->input_dev, ABS_Z, -5760, 5760, 0, 0);
/* temparature */
input_set_abs_params(akm->input_dev, ABS_THROTTLE, -30, 85, 0, 0);
/* status of magnetic sensor */
input_set_abs_params(akm->input_dev, ABS_RUDDER, 0, 3, 0, 0);
/* status of acceleration sensor */
input_set_abs_params(akm->input_dev, ABS_WHEEL, 0, 3, 0, 0);
/* x-axis of raw magnetic vector */
input_set_abs_params(akm->input_dev, ABS_HAT0X, -20480, 20479, 0, 0);
/* y-axis of raw magnetic vector */
input_set_abs_params(akm->input_dev, ABS_HAT0Y, -20480, 20479, 0, 0);
/* z-axis of raw magnetic vector */
input_set_abs_params(akm->input_dev, ABS_BRAKE, -20480, 20479, 0, 0);
akm->input_dev->name = "compass";
err = input_register_device(akm->input_dev);
if (err) {
pr_err("akm8975_probe: Unable to register input device: %s\n",
akm->input_dev->name);
goto exit_input_register_device_failed;
}
err = misc_register(&akmd_device);
if (err) {
pr_err("akm8975_probe: akmd_device register failed\n");
goto exit_misc_device_register_failed;
}
err = misc_register(&akm_aot_device);
if (err) {
pr_err("akm8975_probe: akm_aot_device register failed\n");
goto exit_misc_device_register_failed;
}
err = device_create_file(&client->dev, &dev_attr_akm_ms1);
#ifdef CONFIG_HAS_EARLYSUSPEND
akm->early_suspend.suspend = akm8975_early_suspend;
akm->early_suspend.resume = akm8975_early_resume;
register_early_suspend(&akm->early_suspend);
#endif
return 0;
exit_misc_device_register_failed:
exit_input_register_device_failed:
input_free_device(akm->input_dev);
exit_input_dev_alloc_failed:
akm8975_power_off(akm);
exit_power_on_failed:
kfree(akm);
exit_alloc_data_failed:
exit_check_functionality_failed:
exit_platform_data_null:
return err;
}
static int __devexit akm8975_remove(struct i2c_client *client)
{
struct akm8975_data *akm = i2c_get_clientdata(client);
FUNCDBG("called");
free_irq(client->irq, NULL);
input_unregister_device(akm->input_dev);
misc_deregister(&akmd_device);
misc_deregister(&akm_aot_device);
akm8975_power_off(akm);
kfree(akm);
return 0;
}
static const struct i2c_device_id akm8975_id[] = {
{ "akm8975", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, akm8975_id);
static struct i2c_driver akm8975_driver= {
.probe = akm8975_probe,
.remove = akm8975_remove,
#ifndef CONFIG_HAS_EARLYSUSPEND
.resume = akm8975_resume,
.suspend = akm8975_suspend,
#endif
.id_table = akm8975_id,
.driver = {
.name = "akm8975",
},
};
static int __init akm8975_init(void)
{
pr_info("AK8975 compass driver: init\n");
FUNCDBG("AK8975 compass driver: init\n");
return i2c_add_driver(&akm8975_driver);
}
static void __exit akm8975_exit(void)
{
FUNCDBG("AK8975 compass driver: exit\n");
i2c_del_driver(&akm8975_driver);
}
module_init(akm8975_init);
module_exit(akm8975_exit);
MODULE_AUTHOR("Hou-Kun Chen <hk_chen@htc.com>");
MODULE_DESCRIPTION("AK8975 compass driver");
MODULE_LICENSE("GPL");