AKM8975C源代码

/* 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 <[email protected]>");
MODULE_DESCRIPTION("AK8975 compass driver");
MODULE_LICENSE("GPL");