Remove linear pressure interpolation detection code

Dirk says that divinglog hasn't been doing the linear pressure
interpolation for a long while, so we're doing extra dive fixups that
really aren't needed any more.

Also, the code is actually buggy: it only ever worked on the first
cylinder anyway (because only the first cylinder pressure_delta[] would
be initialized).  That was probably perfectly fine in practice, since
it's unlikely that many tech divers used old versions of divinglog
anyway, so the bug per se isn't a reason to remove it - but it is a sign
that the code was a bit hard to read, so let's get rid of it if there is
no reason to maintain it or fix it.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/dive.c

@@ -1306,17 +1306,12 @@ static void fixup_dc_cylinder_index(struct dive *dive, struct divecomputer *dc)
 	}
 }
 
-/*
+/* Remove redundant pressure information */
- * Simplify dc pressure information:
- *  (a) Remove redundant pressure information
- *  (b) Remove linearly interpolated pressure data
- */
 static void simplify_dc_pressures(struct dive *dive, struct divecomputer *dc)
 {
-	int i, j;
+	int i;
 	int lastindex = -1;
 	int lastpressure = 0, lasto2pressure = 0;
-	int pressure_delta[MAX_CYLINDERS] = { INT_MAX, };
 
 	for (i = 0; i < dc->samples; i++) {
 		struct sample *sample = dc->sample + i;
@@ -1325,60 +1320,17 @@ static void simplify_dc_pressures(struct dive *dive, struct divecomputer *dc)
 		int index;
 
 		index = sample->sensor;
-
 		if (index == lastindex) {
 			/* Remove duplicate redundant pressure information */
 			if (pressure == lastpressure)
 				sample->cylinderpressure.mbar = 0;
 			if (o2_pressure == lasto2pressure)
 				sample->o2cylinderpressure.mbar = 0;
-			/* check for simply linear data in the samples
-			   +INT_MAX means uninitialized, -INT_MAX means not linear */
-			if (pressure_delta[index] != -INT_MAX && lastpressure) {
-				if (pressure_delta[index] == INT_MAX) {
-					pressure_delta[index] = abs(pressure - lastpressure);
-				} else {
-					int cur_delta = abs(pressure - lastpressure);
-					if (cur_delta && abs(cur_delta - pressure_delta[index]) > 150) {
-						/* ok the samples aren't just a linearisation
-						 * between start and end */
-						pressure_delta[index] = -INT_MAX;
-					}
-				}
-			}
 		}
 		lastindex = index;
 		lastpressure = pressure;
 		lasto2pressure = o2_pressure;
 	}
-
-	/* if all the samples for a cylinder have pressure data that
-	 * is basically equidistant throw out the sample cylinder pressure
-	 * information but make sure we still have a valid start and end
-	 * pressure
-	 * this happens when DivingLog decides to linearalize the
-	 * pressure between beginning and end and for strange reasons
-	 * decides to put that in the sample data as if it came from
-	 * the dive computer; we don't want that (we'll visualize with
-	 * constant SAC rate instead)
-	 * WARNING WARNING - I have only seen this in single tank dives
-	 * --- maybe I should try to create a multi tank dive and see what
-	 * --- divinglog does there - but the code right now is only tested
-	 * --- for the single tank case */
-	for (j = 0; j < MAX_CYLINDERS; j++) {
-		if (abs(pressure_delta[j]) != INT_MAX) {
-			cylinder_t *cyl = dive->cylinder + j;
-			for (i = 0; i < dc->samples; i++)
-				if (dc->sample[i].sensor == j)
-					dc->sample[i].cylinderpressure.mbar = 0;
-			if (!cyl->start.mbar)
-				cyl->start.mbar = cyl->sample_start.mbar;
-			if (!cyl->end.mbar)
-				cyl->end.mbar = cyl->sample_end.mbar;
-			cyl->sample_start.mbar = 0;
-			cyl->sample_end.mbar = 0;
-		}
-	}
 }
 
 /* FIXME! sensor -> cylinder mapping? */