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高通HAL层之bmp18x.cpp

时间:2018-02-09 14:49:25      阅读:239      评论:0      收藏:0      [点我收藏+]

标签:节点   reserve   repo   time   reader   首部   lap   instead   缓冲区   

继续上一个链接内容所讲:http://www.cnblogs.com/linhaostudy/p/8430583.html

下面bmp18x sensor为例进行分析。

BMP18x Sensor:

我们以打开bmp180为例,代码为hardware\qcom\sensors\Bmp180.cpp:

 1 PressureSensor::PressureSensor(char *name)
 2     : SensorBase(NULL, "bmp18x"),
 3       mInputReader(4),
 4       mHasPendingEvent(false),
 5       mEnabledTime(0)
 6 {
 7     mPendingEvent.version = sizeof(sensors_event_t);
 8     mPendingEvent.sensor = SENSORS_PRESSURE_HANDLE;
 9     mPendingEvent.type = SENSOR_TYPE_PRESSURE;
10     memset(mPendingEvent.data, 0, sizeof(mPendingEvent.data));
11 
12     if (data_fd) {
13         strlcpy(input_sysfs_path, SYSFS_CLASS, sizeof(input_sysfs_path));
14         strlcat(input_sysfs_path, name, sizeof(input_sysfs_path));
15         strlcat(input_sysfs_path, "/", sizeof(input_sysfs_path));
16         input_sysfs_path_len = strlen(input_sysfs_path);
17         ALOGI("The pressure sensor path is %s",input_sysfs_path);
18         enable(0, 1);
19     }
20 }
21 
22 
23 PressureSensor::PressureSensor(char *name)
24     : SensorBase(NULL, "bmp18x"),
25       mInputReader(4),
26       mHasPendingEvent(false),
27       mEnabledTime(0)
28 {
29     mPendingEvent.version = sizeof(sensors_event_t);
30     mPendingEvent.sensor = SENSORS_PRESSURE_HANDLE;
31     mPendingEvent.type = SENSOR_TYPE_PRESSURE;
32     memset(mPendingEvent.data, 0, sizeof(mPendingEvent.data));
33 
34     if (data_fd) {
35         strlcpy(input_sysfs_path, SYSFS_CLASS, sizeof(input_sysfs_path));
36         strlcat(input_sysfs_path, name, sizeof(input_sysfs_path));
37         strlcat(input_sysfs_path, "/", sizeof(input_sysfs_path));
38         input_sysfs_path_len = strlen(input_sysfs_path);
39         ALOGI("The pressure sensor path is %s",input_sysfs_path);
40         enable(0, 1);
41     }
42 }

 

 

 mPendingEvent是一个sensors_event_t结构体,首先对sensor、type等赋值,然后调用enable打开;

 1 /**
 2  *  @brief        This function will enable/disable sensor.
 3  *  @param[in]    handle
 4  *                  which sensor to enable/disable.
 5  *  @param[in]    en
 6  *                  en=1, enable; 
 7  *                  en=0, disable
 8  *  @return       if the operation is successful.
 9  */
10 int PressureSensor::enable(int32_t handle, int en) 
11 {
12     VFUNC_LOG;
13 
14     int res = 0;
15 
16     LOGV_IF(SYSFS_VERBOSE, "HAL:sysfs:echo %d > %s (%lld)",
17             en, pressureSysFs.pressure_enable, getTimestamp());
18     res = write_sysfs_int(pressureSysFs.pressure_enable, en);
19 
20     return res;
21 }

 

 其实就是对SYSFS_CLASS路径下的文件的enable节点写值“1”;

SYSFS_CLASS的路径为(hardware\qcom\sensors\sensors.h):

1 #define SYSFS_CLASS        "/sys/class/sensors/"

 

 

注意,不要忽略了SensorBase(NULL, "bmp18x"),我们看一下它做了什么?

 1 /*****************************************************************************/
 2 
 3 SensorBase::SensorBase(
 4         const char* dev_name,
 5         const char* data_name,
 6         const struct SensorContext* context /* = NULL */)
 7         : dev_name(dev_name), data_name(data_name), algo(NULL),
 8         dev_fd(-1), data_fd(-1), mEnabled(0), mHasPendingMetadata(0)
 9 {
10         if (context != NULL) {
11                 CalibrationManager& cm(CalibrationManager::getInstance());
12                 algo = cm.getCalAlgo(context->sensor);
13 
14                 /* Set up the sensors_meta_data_event_t event*/
15                 meta_data.version = META_DATA_VERSION;
16                 meta_data.sensor = context->sensor->handle;
17                 meta_data.type = SENSOR_TYPE_META_DATA;
18                 meta_data.reserved0 = 0;
19                 meta_data.timestamp = 0LL;
20                 meta_data.meta_data.what = META_DATA_FLUSH_COMPLETE;
21                 meta_data.meta_data.sensor = context->sensor->handle;
22         }
23 
24         if (data_name) {
25                 data_fd = openInput(data_name);
26         }
27 }

 

这里的dev_name为NULL,data_name为bmp18x,设置dev_name和data_name后调用openInput打开设备:

技术分享图片SensorBase::openInput

  再继续看一下getInput:

技术分享图片getInput

 这个函数的作用就是打开"/dev/input",查找其中的输入设备名字与传入参数匹配的那一个,这里是"bmp18x",并返回相应的打开句柄。

 到这里sensor就打开了;

 

Activate、setDelay都是直接调用相应的sensor接口直接调用相应sensor的接口,主要是readEvents:

 1 int PressureSensor::readEvents(sensors_event_t* data, int count)
 2 {
 3     if (count < 1)
 4         return -EINVAL;
 5 
 6     if (mHasPendingEvent) {
 7         mHasPendingEvent = false;
 8         mPendingEvent.timestamp = getTimestamp();
 9         *data = mPendingEvent;
10         return mEnabled ? 1 : 0;
11     }
12 
13     if (mHasPendingMetadata) {
14         mHasPendingMetadata--;
15         meta_data.timestamp = getTimestamp();
16         *data = meta_data;
17         return mEnabled ? 1 : 0;
18     }
19 
20     ssize_t n = mInputReader.fill(data_fd);  //从输入设备中读取数据  
21     if (n < 0)
22         return n;
23 
24     int numEventReceived = 0;
25     input_event const* event;
26 
27 #if FETCH_FULL_EVENT_BEFORE_RETURN
28 again:
29 #endif
30     while (count && mInputReader.readEvent(&event)) {//读取当前一个event,返回还有的数据大小  
31         int type = event->type;
32         if (type == EV_ABS) {//根据kernel上报的input事件来确定相应的数据值
33             float value = event->value;
34             mPendingEvent.pressure = value * CONVERT_PRESSURE;
35         } else if (type == EV_SYN) {
36             switch (event->code) {
37                 case SYN_TIME_SEC:
38                     mUseAbsTimeStamp = true;
39                     report_time = event->value*1000000000LL;
40                     break;
41                 case SYN_TIME_NSEC:
42                     mUseAbsTimeStamp = true;
43                     mPendingEvent.timestamp = report_time+event->value;
44                     break;
45                 case SYN_REPORT:
46                     if(mUseAbsTimeStamp != true) {
47                         mPendingEvent.timestamp = timevalToNano(event->time);
48                     }
49                     if (mEnabled) {
50                         if (mPendingEvent.timestamp >= mEnabledTime) {
51                             *data++ = mPendingEvent;
52                             numEventReceived++;
53                         }
54                         count--;
55                     }
56                     break;
57             }
58         } else {
59             ALOGE("PressureSensor: unknown event (type=%d, code=%d)",
60                     type, event->code);
61         }
62         mInputReader.next();
63     }
64 
65 #if FETCH_FULL_EVENT_BEFORE_RETURN
66     /* if we didn‘t read a complete event, see if we can fill and
67        try again instead of returning with nothing and redoing poll. */
68     if (numEventReceived == 0 && mEnabled == 1) {
69         n = mInputReader.fill(data_fd);
70         if (n)
71             goto again;
72     }
73 #endif
74 
75     return numEventReceived;
76 }

 

这里看一下mInputReader,是一个InputEventCircularReader结构,表示的是一个环形的读入数据缓冲区:

 1 ssize_t InputEventCircularReader::fill(int fd)
 2 {
 3     size_t numEventsRead = 0;
 4     if (mFreeSpace) {
 5         const ssize_t nread = read(fd, mHead, mFreeSpace * sizeof(input_event));//读取数据
 6         if (nread<0 || nread % sizeof(input_event)) {
 7             // we got a partial event!!
 8             return nread<0 ? -errno : -EINVAL;
 9         }
10 
11         numEventsRead = nread / sizeof(input_event);
12         // dumpEvents(mHead, numEventsRead);
13         D("nread = %ld, numEventsRead = %d.", nread, numEventsRead);
14         if (numEventsRead) {
15             mHead += numEventsRead;
16             mFreeSpace -= numEventsRead;
17             if (mHead > mBufferEnd) {
18                 size_t s = mHead - mBufferEnd;
19                 memcpy(mBuffer, mBufferEnd, s * sizeof(input_event));
20                 mHead = mBuffer + s;
21             }
22         }
23     }
24 
25     return numEventsRead;
26 }

mCurr表示未读事件的第一个,初始为缓冲区首部;

Fill函数是把调用read从相应的输入设备读入数据mHead位置;

readEvent函数返回mCurr和剩余的数据大小;

next函数让mCurr移一个input_event;

 

 

高通HAL层之bmp18x.cpp

标签:节点   reserve   repo   time   reader   首部   lap   instead   缓冲区   

原文地址:https://www.cnblogs.com/linhaostudy/p/8432741.html

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