From 8064c4f33ad0fd47631877d85ea138b556b09424 Mon Sep 17 00:00:00 2001
From: Kieran Bingham <kieran.bingham@ideasonboard.com>
Date: Thu, 19 Feb 2026 15:05:16 +0000
Subject: [PATCH] ipa: libipa: fixedpoint: Move float conversion inline

With all users of the floatingToFixedPoint and fixedToFloatingPoint
calls converted to use the FixedPoint Quantized types, remove the calls
and documentation and move the implementation inline in the
FixedPointTraits implementation.

Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/ipa/libipa/fixedpoint.cpp | 22 ----------
 src/ipa/libipa/fixedpoint.h   | 75 ++++++++++-------------------------
 2 files changed, 22 insertions(+), 75 deletions(-)

diff --git a/src/ipa/libipa/fixedpoint.cpp b/src/ipa/libipa/fixedpoint.cpp
index b581ca84..b06ad8d2 100644
--- a/src/ipa/libipa/fixedpoint.cpp
+++ b/src/ipa/libipa/fixedpoint.cpp
@@ -15,28 +15,6 @@ namespace libcamera {
 
 namespace ipa {
 
-/**
- * \fn R floatingToFixedPoint(T number)
- * \brief Convert a floating point number to a fixed-point representation
- * \tparam I Bit width of the integer part of the fixed-point
- * \tparam F Bit width of the fractional part of the fixed-point
- * \tparam R Return type of the fixed-point representation
- * \tparam T Input type of the floating point representation
- * \param number The floating point number to convert to fixed point
- * \return The converted value
- */
-
-/**
- * \fn R fixedToFloatingPoint(T number)
- * \brief Convert a fixed-point number to a floating point representation
- * \tparam I Bit width of the integer part of the fixed-point
- * \tparam F Bit width of the fractional part of the fixed-point
- * \tparam R Return type of the floating point representation
- * \tparam T Input type of the fixed-point representation
- * \param number The fixed point number to convert to floating point
- * \return The converted value
- */
-
 /**
  * \struct libcamera::ipa::FixedPointQTraits
  * \brief Traits type implementing fixed-point quantization conversions
diff --git a/src/ipa/libipa/fixedpoint.h b/src/ipa/libipa/fixedpoint.h
index df685e85..ed8aca9f 100644
--- a/src/ipa/libipa/fixedpoint.h
+++ b/src/ipa/libipa/fixedpoint.h
@@ -16,55 +16,6 @@ namespace libcamera {
 
 namespace ipa {
 
-#ifndef __DOXYGEN__
-template<unsigned int I, unsigned int F, typename R, typename T,
-	 std::enable_if_t<std::is_integral_v<R> &&
-			  std::is_floating_point_v<T>> * = nullptr>
-#else
-template<unsigned int I, unsigned int F, typename R, typename T>
-#endif
-constexpr R floatingToFixedPoint(T number)
-{
-	static_assert(sizeof(int) >= sizeof(R));
-	static_assert(I + F <= sizeof(R) * 8);
-
-	/*
-	 * The intermediate cast to int is needed on arm platforms to properly
-	 * cast negative values. See
-	 * https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/
-	 */
-	R mask = (1 << (F + I)) - 1;
-	R frac = static_cast<R>(static_cast<int>(std::round(number * (1 << F)))) & mask;
-
-	return frac;
-}
-
-#ifndef __DOXYGEN__
-template<unsigned int I, unsigned int F, typename R, typename T,
-	 std::enable_if_t<std::is_floating_point_v<R> &&
-			  std::is_integral_v<T>> * = nullptr>
-#else
-template<unsigned int I, unsigned int F, typename R, typename T>
-#endif
-constexpr R fixedToFloatingPoint(T number)
-{
-	static_assert(sizeof(int) >= sizeof(T));
-	static_assert(I + F <= sizeof(T) * 8);
-
-	if constexpr (std::is_unsigned_v<T>)
-		return static_cast<R>(number) / static_cast<R>(T{ 1 } << F);
-
-	/*
-	 * Recreate the upper bits in case of a negative number by shifting the sign
-	 * bit from the fixed point to the first bit of the unsigned and then right shifting
-	 * by the same amount which keeps the sign bit in place.
-	 * This can be optimized by the compiler quite well.
-	 */
-	int remaining_bits = sizeof(int) * 8 - (I + F);
-	int t = static_cast<int>(static_cast<unsigned>(number) << remaining_bits) >> remaining_bits;
-	return static_cast<R>(t) / static_cast<R>(1 << F);
-}
-
 template<unsigned int I, unsigned int F, typename T>
 struct FixedPointQTraits {
 private:
@@ -97,11 +48,23 @@ public:
 
 	static constexpr float toFloat(QuantizedType q)
 	{
-		return fixedToFloatingPoint<I, F, float, T>(q);
+		if constexpr (std::is_unsigned_v<T>)
+			return static_cast<float>(q) / static_cast<float>(UT{ 1 } << F);
+
+		/*
+		 * Recreate the upper bits in case of a negative number by
+		 * shifting the sign bit from the fixed point to the first bit
+		 * of the unsigned and then right shifting by the same amount
+		 * which keeps the sign bit in place. This can be optimized by
+		 * the compiler quite well.
+		 */
+		unsigned int remaining_bits = sizeof(UT) * 8 - (I + F);
+		T t = static_cast<T>(static_cast<UT>(q) << remaining_bits) >> remaining_bits;
+		return static_cast<float>(t) / static_cast<float>(UT{ 1 } << F);
 	}
 
-	static constexpr float min = fixedToFloatingPoint<I, F, float>(static_cast<T>(qMin));
-	static constexpr float max = fixedToFloatingPoint<I, F, float>(static_cast<T>(qMax));
+	static constexpr float min = toFloat(qMin);
+	static constexpr float max = toFloat(qMax);
 
 	static_assert(min < max, "FixedPointQTraits: Minimum must be less than maximum");
 
@@ -109,7 +72,13 @@ public:
 	static QuantizedType fromFloat(float v)
 	{
 		v = std::clamp(v, min, max);
-		return floatingToFixedPoint<I, F, T, float>(v);
+
+		/*
+		 * The intermediate cast to int is needed on arm platforms to
+		 * properly cast negative values. See
+		 * https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/
+		 */
+		return static_cast<UT>(static_cast<T>(std::round(v * (1 << F)))) & bitMask;
 	}
 };