battery: User power/current reading from battery

This switches to always use the power/current reading if we had a
sensible reading at some point in the past.

In contrast to the older UPower code, will will however ignore the
reading for 10 seconds after a discontinuity (power plug/unplug or
resume) unless we read an explicit zero value after the event happened.

We do this under the assumption that the readings may be wildly off, and
it is better to not show an estimate rather than one that is wildly
incorrect.

Note that this commit also normalises negative power readings while
discharging to be positive.

Closes: #199

2 files changed, 38 insertions, 7 deletions

diff --git a/src/up-constants.h b/src/up-constants.h
index 660e7fd..fdd2e0e 100644
--- a/src/up-constants.h
+++ b/src/up-constants.h
@@ -32,6 +32,8 @@ G_BEGIN_DECLS
 #define UP_DAEMON_SHORT_TIMEOUT				  30 /* seconds */
 #define UP_DAEMON_LONG_TIMEOUT				 120 /* seconds */
 
+#define UP_DAEMON_DISTRUST_RATE_TIMEOUT			  10 /* second */
+
 #define UP_FULLY_CHARGED_THRESHOLD			  90 /* % */
 #define UP_DAEMON_EPSILON				0.01 /* I can't believe it's not zero */
 
diff --git a/src/up-device-battery.c b/src/up-device-battery.c
index c88a276..5874901 100644
--- a/src/up-device-battery.c
+++ b/src/up-device-battery.c
@@ -46,6 +46,9 @@ typedef struct {
 	gdouble energy_design;
 	gint charge_cycles;
 
+	gboolean trust_power_measurement;
+	gint64 last_power_discontinuity;
+
 	/* dynamic values */
 	gint64 fast_repoll_until;
 	gboolean repoll_needed;
@@ -160,7 +163,7 @@ up_device_battery_estimate_power (UpDeviceBattery *self, UpBatteryValues *cur)
 			cur->state = UP_DEVICE_STATE_CHARGING;
 	}
 
-	/* The rate is defined to be positive during both charge and discharge. */
+	/* QUIRK: No good reason, but define rate to be positive. */
 	if (cur->state == UP_DEVICE_STATE_DISCHARGING)
 		energy_rate *= -1.0;
 
@@ -236,14 +239,20 @@ up_device_battery_report (UpDeviceBattery *self,
 		return;
 	}
 
-	/* Discard all old measurements that can't be used for estimations. */
-	if (reason == UP_REFRESH_RESUME || reason == UP_REFRESH_LINE_POWER)
-		priv->hw_data_len = 0;
-
 	g_assert (priv->units != UP_BATTERY_UNIT_UNDEFINED);
 
 	values->ts_us = g_get_monotonic_time ();
 
+	/* Discard all old measurements that can't be used for estimations.
+	 *
+	 * XXX: Should a state change also trigger an update of the timestamp
+	 *      that is used to discard power/current measurements?
+	 */
+	if (reason == UP_REFRESH_RESUME || reason == UP_REFRESH_LINE_POWER) {
+		priv->hw_data_len = 0;
+		priv->last_power_discontinuity = values->ts_us;
+	}
+
 	/* QUIRK:
 	 *
 	 * There is an old bug where some Lenovo machine switched from reporting
@@ -312,8 +321,27 @@ up_device_battery_report (UpDeviceBattery *self,
 	 * about the AC state and we only have "one" battery.
 	 */
 
-	/* Do power estimations based on energy/charge data */
-	up_device_battery_estimate_power (self, values);
+	/* QUIRK: No good reason, but define rate to be positive.
+	 *
+	 * It would be sane/reasonable to define it to be negative when
+	 * discharging. Only odd thing is that most common hardware appears
+	 * to always report positive values, which appeared in DBus unmodified.
+	 */
+	if (values->state == UP_DEVICE_STATE_DISCHARGING && values->energy.rate < 0)
+		values->energy.rate = -values->energy.rate;
+
+	/* NOTE: We got a (likely sane) reading.
+	 * Assume power/current readings are accurate from now on. */
+	if (values->energy.rate > 0.01)
+		priv->trust_power_measurement = TRUE;
+
+	if (priv->trust_power_measurement) {
+		/* QUIRK: Do not trust readings after a discontinuity happened */
+		if (priv->last_power_discontinuity + UP_DAEMON_DISTRUST_RATE_TIMEOUT * G_USEC_PER_SEC > values->ts_us)
+			values->energy.rate = 0.0;
+	} else {
+		up_device_battery_estimate_power (self, values);
+	}
 
 
 	/* Push into our ring buffer */
@@ -467,6 +495,7 @@ up_device_battery_update_info (UpDeviceBattery *self, UpBatteryInfo *info)
 		/* NOTE: Assume a normal refresh will follow immediately (do not update timestamp). */
 	} else {
 		priv->present = FALSE;
+		priv->trust_power_measurement = FALSE;
 		priv->hw_data_len = 0;
 		priv->units = UP_BATTERY_UNIT_UNDEFINED;