math: Add/expose some vector operation

Expose dot procdut and cros product for vector operations.

BUG=b:120346412
BRANCH=none
TEST=compile, check unit tests.

Change-Id: Ief50f31aa6105dc2f0d92caf8b7473a7e141eb45
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1387923
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>

2 files changed, 41 insertions, 4 deletions

diff --git a/common/math_util.c b/common/math_util.c
index 5e45f9efad..1a29c63d49 100644
--- a/common/math_util.c
+++ b/common/math_util.c
@@ -148,6 +148,28 @@ int vector_magnitude(const intv3_t v)
 	return int_sqrtf(sum);
 }
 
+/* cross_product only works if the vectors magnitudes are around 1<<16. */
+void cross_product(const intv3_t v1, const intv3_t v2, intv3_t v)
+{
+	v[X] = (fp_inter_t)v1[Y] * v2[Z] - (fp_inter_t)v1[Z] * v2[Y];
+	v[Y] = (fp_inter_t)v1[Z] * v2[X] - (fp_inter_t)v1[X] * v2[Z];
+	v[Z] = (fp_inter_t)v1[X] * v2[Y] - (fp_inter_t)v1[Y] * v2[X];
+}
+
+fp_inter_t dot_product(const intv3_t v1, const intv3_t v2)
+{
+	return (fp_inter_t)v1[X] * v2[X] +
+	       (fp_inter_t)v1[Y] * v2[Y] +
+	       (fp_inter_t)v1[Z] * v2[Z];
+}
+
+void vector_scale(intv3_t v, fp_t s)
+{
+	v[X] = fp_mul(v[X], s);
+	v[Y] = fp_mul(v[Y], s);
+	v[Z] = fp_mul(v[Z], s);
+}
+
 fp_t cosine_of_angle_diff(const intv3_t v1, const intv3_t v2)
 {
 	fp_inter_t dotproduct;
@@ -157,10 +179,7 @@ fp_t cosine_of_angle_diff(const intv3_t v1, const intv3_t v2)
 	 * Angle between two vectors is acos(A dot B / |A|*|B|). To return
 	 * cosine of angle between vectors, then don't do acos operation.
 	 */
-
-	dotproduct =	(fp_inter_t)v1[0] * v2[0] +
-			(fp_inter_t)v1[1] * v2[1] +
-			(fp_inter_t)v1[2] * v2[2];
+	dotproduct = dot_product(v1, v2);
 
 	denominator = (fp_inter_t)vector_magnitude(v1) * vector_magnitude(v2);
 
diff --git a/include/math_util.h b/include/math_util.h
index 942aaf8908..8d779846b3 100644
--- a/include/math_util.h
+++ b/include/math_util.h
@@ -151,6 +151,24 @@ enum {
 fp_t arc_cos(fp_t x);
 
 /**
+ * Calculate the dot product of 2 vectors.
+ */
+fp_inter_t dot_product(const intv3_t v1, const intv3_t v2);
+
+/*
+ * Calculate the dot product of 2 vectors,
+ *
+ * Assume the result vector components fits in 32bit.
+ */
+void cross_product(const intv3_t v1, const intv3_t v2, intv3_t v);
+
+/**
+ * Scale a vector by fixed point constant.
+ */
+void vector_scale(intv3_t v, fp_t s);
+
+
+/**
  * Find the cosine of the angle between two vectors.
  *
  * The implementation assumes no vector component is greater than