sensor: poll for POLLOUT event before writing pipe

Poll with timeout = -1 for flush complete event and timeout = 1000
for regular sensor event

flush requests are tracked with vector. This requires to include stlport.
As stlport olverloads pow(), all calls to this function are also modified
to avoid ambiguous calls.

Change-Id: I4f8bd97289dbc3e18b5fb0911aa84bde4f401ad8
Signed-off-by: Like Yan <like.yan@intel.com>

1 files changed, 52 insertions, 9 deletions

diff --git a/libsensors_iio/src/SensorBase.cpp b/libsensors_iio/src/SensorBase.cpp
index 992d3d4..bfee207 100644
--- a/libsensors_iio/src/SensorBase.cpp
+++ b/libsensors_iio/src/SensorBase.cpp
@@ -369,9 +369,43 @@ bool SensorBase::FillSensor_tData(struct sensor_t *data)
 	return true;
 }
 
-int SensorBase::FlushData(bool)
+int SensorBase::WritePipeWithPoll(sensors_event_t *event_data, int size, int timeout)
 {
 	int err;
+	struct pollfd poll_fd;
+
+	poll_fd.fd = android_pipe_fd;
+	poll_fd.events = POLLOUT;
+
+	err = poll(&poll_fd, (unsigned long)1, timeout);
+	if (err < 0) {
+		ALOGE("%s: error happened when polling pipe, errno: %d.", android_name, errno);
+		return err;
+	}
+
+	if (err == 0) {
+		ALOGE("%s: polling pipe timeout, timeout = %d.", android_name, timeout);
+		return err;
+	}
+
+	if (poll_fd.revents&POLLOUT) {
+		err = write(android_pipe_fd, event_data, size);
+		if (err <= 0) {
+			ALOGE("%s: Failed to write to pipe, timeout: %d, errno: %d.",
+				android_name, timeout, errno);
+			return err;
+		}
+	} else {
+		ALOGE("%s: polling was breaked by unexpected event: %d", android_name, poll_fd.revents);
+		return -EAGAIN;
+	}
+
+	return err;
+}
+
+int SensorBase::FlushData(bool)
+{
+	int err = 0, retry = 3;
 	sensors_event_t flush_event_data;
 
 	flush_event_data.sensor = 0;
@@ -381,14 +415,22 @@ int SensorBase::FlushData(bool)
 	flush_event_data.type = SENSOR_TYPE_META_DATA;
 	flush_event_data.version = META_DATA_VERSION;
 
-	err = write(android_pipe_fd, &flush_event_data, sizeof(sensor_event));
-	if (err < 0) {
-		ALOGE("%s: Failed to write flush event data to pipe.", android_name);
-		return err;
+	while (retry) {
+		err = WritePipeWithPoll(&flush_event_data, sizeof(sensor_event),
+						POLL_TIMEOUT_FLUSH_EVENT);
+		if (err > 0)
+			break;
+
+		retry--;
+		ALOGI("%s: Retry writing flush event data to pipe, retry_cnt: %d.", android_name, 3-retry);
 	}
 
-	ALOGD("SensorBase::FlushData completed.");
-	return 0;
+	if (retry == 0)
+		ALOGE("%s: Failed to write flush event data to pipe, err=%d.", android_name, err);
+	else
+		ALOGD("SensorBase::FlushData completed.");
+
+	return err;
 }
 
 void SensorBase::WriteDataToPipe()
@@ -399,8 +441,9 @@ void SensorBase::WriteDataToPipe()
 		return;
 
 	if (sensor_event.timestamp > last_data_timestamp) {
-		err = write(android_pipe_fd, &sensor_event, sizeof(sensor_event));
-		if (err < 0) {
+		err = WritePipeWithPoll(&sensor_event, sizeof(sensor_event),
+						POLL_TIMEOUT_DATA_EVENT);
+		if (err <= 0) {
 			ALOGE("%s: Failed to write sensor data to pipe.", android_name);
 			return;
 		}