STPK-1429 Limit firing rate for poll-mode sensors

Don't refresh values associated to poll-mode sensors, and don't
raise the flag that will cause an event to be propagated upwards,
until an amount of time consistent with the sensor sampling rate
has elapsed since an event was last reported in relation to this
sensor.

This takes care of scenarios such as a low refresh rate poll-mode
sensor and a high refresh rate device-driven sensor being both
enabled, and a lot of events (and sysfs reads) being generated
for the low refresh rate sensor without a good reason to do so.

Issue: STPK-1429

Change-Id: I2bac3a8efd8da79bc642945b085408c29072d8c2
Signed-off-by: Patrick Porlan <patrick.porlan@intel.com>

diff --git a/control.c b/control.c
index 8ef84d3..9b6d2fd 100644 (file)
--- a/control.c
+++ b/control.c
@@ -464,13 +464,14 @@ static void propagate_sensor_report(int s, struct sensors_event_t* data)
        int num_fields;
        int c;
        unsigned char* current_sample;
+       int64_t current_ts = get_timestamp();
 
        memset(data, 0, sizeof(sensors_event_t));
 
        data->version = sizeof(sensors_event_t);
        data->sensor = s;
        data->type = sensor_type;
-       data->timestamp = get_timestamp();
+       data->timestamp = current_ts;
 
        switch (sensor_type) {
                case SENSOR_TYPE_ACCELEROMETER:         /* m/s^2        */
@@ -506,7 +507,7 @@ static void propagate_sensor_report(int s, struct sensors_event_t* data)
        ALOGV("Sample on sensor %d (type %d):\n", s, sensor_type);
 
        /* Take note of current time counter value for rate control purposes */
-       sensor_info[s].last_integration_ts = get_timestamp();
+       sensor_info[s].last_integration_ts = current_ts;
 
        /* If we're dealing with a poll-mode sensor */
        if (!sensor_info[s].num_channels) {
@@ -592,6 +593,7 @@ int sensor_poll(struct sensors_event_t* data, int count)
        int nfds;
        int delta;
        struct epoll_event ev[MAX_DEVICES];
+       int64_t target_ts;
 
        /* Get one or more events from our collection of sensors */
 
@@ -639,12 +641,18 @@ await_event:
                                integrate_device_report(ev[i].data.u32);
                }
 
-       /* It's a good time to invalidate poll-mode sensor values */
+       /* Check poll-mode sensors and fire up an event if it's time to do so */
        if (active_poll_sensors)
                for (s=0; s<sensor_count; s++)
                        if (sensor_info[s].enable_count &&
-                               !sensor_info[s].num_channels)
+                           !sensor_info[s].num_channels &&
+                           sensor_info[s].sampling_rate) {
+                               target_ts = sensor_info[s].last_integration_ts +
+                                     1000000000LL/sensor_info[s].sampling_rate;
+
+                               if (last_poll_exit_ts >= target_ts)
                                        sensor_info[s].report_pending = 1;
+                       }
 
        goto return_first_available_sensor_report;
 }