CRAS: Add a configurable volume curve.

Create a new type of volume curve that allows for configurable max
volume and step size for each volume step.

BUG=chrome-os-partner:8155
TEST=updated volume curve unit tests.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Change-Id: Iec7aea4793d15bbb730442f4c0d9ebf6b69eacff

3 files changed, 48 insertions, 0 deletions

diff --git a/cras/src/server/cras_volume_curve.c b/cras/src/server/cras_volume_curve.c
index b6719c75..3f7f385d 100644
--- a/cras/src/server/cras_volume_curve.c
+++ b/cras/src/server/cras_volume_curve.c
@@ -18,6 +18,19 @@ static long get_dBFS_default(const struct cras_volume_curve *curve,
 	return (volume - 100) * 100;
 }
 
+/* Simple curve with configurable max volume and volume step. */
+struct stepped_curve {
+	struct cras_volume_curve curve;
+	long max_vol;
+	long step;
+};
+
+static long get_dBFS_step(const struct cras_volume_curve *curve, size_t volume)
+{
+	const struct stepped_curve *c = (const struct stepped_curve *)curve;
+	return c->max_vol - (c->step * (100 - volume));
+}
+
 /*
  * Exported Interface.
  */
@@ -31,6 +44,20 @@ struct cras_volume_curve *cras_volume_curve_create_default()
 	return curve;
 }
 
+struct cras_volume_curve *cras_volume_curve_create_simple_step(
+		long max_volume,
+		long volume_step)
+{
+	struct stepped_curve *curve;
+	curve = (struct stepped_curve *)calloc(1, sizeof(*curve));
+	if (curve == NULL)
+		return NULL;
+	curve->curve.get_dBFS = get_dBFS_step;
+	curve->max_vol = max_volume;
+	curve->step = volume_step;
+	return &curve->curve;
+}
+
 void cras_volume_curve_destroy(struct cras_volume_curve *curve)
 {
 	free(curve);
diff --git a/cras/src/server/cras_volume_curve.h b/cras/src/server/cras_volume_curve.h
index a6a08c72..9683136c 100644
--- a/cras/src/server/cras_volume_curve.h
+++ b/cras/src/server/cras_volume_curve.h
@@ -25,6 +25,15 @@ struct cras_volume_curve {
  */
 struct cras_volume_curve *cras_volume_curve_create_default();
 
+/* Creates a volume curve with a specified max volume and step.
+ * Args:
+ *    max_volume - Maximum volume allowed in dBFS.
+ *    volume_step - Number of dB to change for one volume tick.
+ */
+struct cras_volume_curve *cras_volume_curve_create_simple_step(
+		long max_volume,
+		long volume_step);
+
 /* Destroys a curve created with cras_volume_curve_create_*.
  * Args:
  *    curve - The curve to destroy.
diff --git a/cras/src/tests/volume_curve_unittest.cc b/cras/src/tests/volume_curve_unittest.cc
index f25d9563..5f40666d 100644
--- a/cras/src/tests/volume_curve_unittest.cc
+++ b/cras/src/tests/volume_curve_unittest.cc
@@ -19,6 +19,18 @@ TEST(VolumeCurve, DefaultCurve) {
   EXPECT_EQ(0, curve->get_dBFS(curve, 100));
   EXPECT_EQ(-10000, curve->get_dBFS(curve, 0));
   EXPECT_EQ(-2500, curve->get_dBFS(curve, 75));
+  cras_volume_curve_destroy(curve);
+}
+
+TEST(VolumeCurve, SteppedCurve) {
+  struct cras_volume_curve *curve;
+  curve = cras_volume_curve_create_simple_step(-600, 75);
+  ASSERT_NE(static_cast<struct cras_volume_curve *>(NULL), curve);
+  EXPECT_EQ(-600 - 50 * 75, curve->get_dBFS(curve, 50));
+  EXPECT_EQ(-600, curve->get_dBFS(curve, 100));
+  EXPECT_EQ(-600 - 100 * 75, curve->get_dBFS(curve, 0));
+  EXPECT_EQ(-600 - 25 * 75, curve->get_dBFS(curve, 75));
+  cras_volume_curve_destroy(curve);
 }
 
 }  //  namespace