fixp-arith: add a linear interpolation function
Adds a function to interpolate against two points,
this is carried arount as a helper function by tons of drivers.
Signed-off-by: Craig Tatlor <[email protected]>
Signed-off-by: Dmitry Baryshkov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>
diff --git a/include/linux/fixp-arith.h b/include/linux/fixp-arith.h
index 8396013..281cb4f 100644
--- a/include/linux/fixp-arith.h
+++ b/include/linux/fixp-arith.h
@@ -141,4 +141,23 @@ static inline s32 fixp_sin32_rad(u32 radians, u32 twopi)
#define fixp_cos32_rad(rad, twopi) \
fixp_sin32_rad(rad + twopi / 4, twopi)
+/**
+ * fixp_linear_interpolate() - interpolates a value from two known points
+ *
+ * @x0: x value of point 0
+ * @y0: y value of point 0
+ * @x1: x value of point 1
+ * @y1: y value of point 1
+ * @x: the linear interpolant
+ */
+static inline int fixp_linear_interpolate(int x0, int y0, int x1, int y1, int x)
+{
+ if (y0 == y1 || x == x0)
+ return y0;
+ if (x1 == x0 || x == x1)
+ return y1;
+
+ return y0 + ((y1 - y0) * (x - x0) / (x1 - x0));
+}
+
#endif
