[{"id":38233,"web_url":"https://patchwork.libcamera.org/comment/38233/","msgid":"<177149201420.607498.18166300659961304883@neptunite.rasen.tech>","date":"2026-02-19T09:06:54","subject":"Re: [PATCH v7 15/15] ipa: libipa: fixedpoint: Move float conversion\n\tinline","submitter":{"id":17,"url":"https://patchwork.libcamera.org/api/people/17/","name":"Paul Elder","email":"paul.elder@ideasonboard.com"},"content":"Quoting Kieran Bingham (2026-02-14 01:57:54)\n> With all users of the floatingToFixedPoint and fixedToFloatingPoint\n> calls converted to use the FixedPoint Quantized types, remove the calls\n> and documentation and move the implementation inline in the\n> FixedPointTraits implementation.\n> \n> Reviewed-by: Isaac Scott \n> Reviewed-by: Laurent Pinchart \n> Signed-off-by: Kieran Bingham \n\nReviewed-by: Paul Elder \n\n> \n> ---\n> v5:\n> - Reflow text when moved\n> \n> v6:\n> - Use UT{1} << F instead of 1 << F\n> ---\n> src/ipa/libipa/fixedpoint.cpp | 22 -------------\n> src/ipa/libipa/fixedpoint.h | 75 +++++++++++++------------------------------\n> 2 files changed, 22 insertions(+), 75 deletions(-)\n> \n> diff --git a/src/ipa/libipa/fixedpoint.cpp b/src/ipa/libipa/fixedpoint.cpp\n> index caa9ce0fc1ec..7eee3614df6a 100644\n> --- a/src/ipa/libipa/fixedpoint.cpp\n> +++ b/src/ipa/libipa/fixedpoint.cpp\n> @@ -15,28 +15,6 @@ namespace libcamera {\n> \n> namespace ipa {\n> \n> -/**\n> - * \\fn R floatingToFixedPoint(T number)\n> - * \\brief Convert a floating point number to a fixed-point representation\n> - * \\tparam I Bit width of the integer part of the fixed-point\n> - * \\tparam F Bit width of the fractional part of the fixed-point\n> - * \\tparam R Return type of the fixed-point representation\n> - * \\tparam T Input type of the floating point representation\n> - * \\param number The floating point number to convert to fixed point\n> - * \\return The converted value\n> - */\n> -\n> -/**\n> - * \\fn R fixedToFloatingPoint(T number)\n> - * \\brief Convert a fixed-point number to a floating point representation\n> - * \\tparam I Bit width of the integer part of the fixed-point\n> - * \\tparam F Bit width of the fractional part of the fixed-point\n> - * \\tparam R Return type of the floating point representation\n> - * \\tparam T Input type of the fixed-point representation\n> - * \\param number The fixed point number to convert to floating point\n> - * \\return The converted value\n> - */\n> -\n> /**\n> * \\struct libcamera::ipa::FixedPointQTraits\n> * \\brief Traits type implementing fixed-point quantisation conversions\n> diff --git a/src/ipa/libipa/fixedpoint.h b/src/ipa/libipa/fixedpoint.h\n> index b6b611df7fc3..a0da31209271 100644\n> --- a/src/ipa/libipa/fixedpoint.h\n> +++ b/src/ipa/libipa/fixedpoint.h\n> @@ -16,55 +16,6 @@ namespace libcamera {\n> \n> namespace ipa {\n> \n> -#ifndef __DOXYGEN__\n> -template - std::enable_if_t &&\n> - std::is_floating_point_v> * = nullptr>\n> -#else\n> -template\n> -#endif\n> -constexpr R floatingToFixedPoint(T number)\n> -{\n> - static_assert(sizeof(int) >= sizeof(R));\n> - static_assert(I + F <= sizeof(R) * 8);\n> -\n> - /*\n> - * The intermediate cast to int is needed on arm platforms to properly\n> - * cast negative values. See\n> - * https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/\n> - */\n> - R mask = (1 << (F + I)) - 1;\n> - R frac = static_cast(static_cast(std::round(number * (1 << F)))) & mask;\n> -\n> - return frac;\n> -}\n> -\n> -#ifndef __DOXYGEN__\n> -template - std::enable_if_t &&\n> - std::is_integral_v> * = nullptr>\n> -#else\n> -template\n> -#endif\n> -constexpr R fixedToFloatingPoint(T number)\n> -{\n> - static_assert(sizeof(int) >= sizeof(T));\n> - static_assert(I + F <= sizeof(T) * 8);\n> -\n> - if constexpr (std::is_unsigned_v)\n> - return static_cast(number) / static_cast(T{ 1 } << F);\n> -\n> - /*\n> - * Recreate the upper bits in case of a negative number by shifting the sign\n> - * bit from the fixed point to the first bit of the unsigned and then right shifting\n> - * by the same amount which keeps the sign bit in place.\n> - * This can be optimized by the compiler quite well.\n> - */\n> - int remaining_bits = sizeof(int) * 8 - (I + F);\n> - int t = static_cast(static_cast(number) << remaining_bits) >> remaining_bits;\n> - return static_cast(t) / static_cast(1 << F);\n> -}\n> -\n> template\n> struct FixedPointQTraits {\n> private:\n> @@ -97,11 +48,23 @@ public:\n> \n> static constexpr float toFloat(QuantizedType q)\n> {\n> - return fixedToFloatingPoint(q);\n> + if constexpr (std::is_unsigned_v)\n> + return static_cast(q) / static_cast(UT{ 1 } << F);\n> +\n> + /*\n> + * Recreate the upper bits in case of a negative number by\n> + * shifting the sign bit from the fixed point to the first bit\n> + * of the unsigned and then right shifting by the same amount\n> + * which keeps the sign bit in place. This can be optimized by\n> + * the compiler quite well.\n> + */\n> + unsigned int remaining_bits = sizeof(UT) * 8 - (I + F);\n> + T t = static_cast(static_cast(q) << remaining_bits) >> remaining_bits;\n> + return static_cast(t) / static_cast(UT{ 1 } << F);\n> }\n> \n> - static constexpr float min = fixedToFloatingPoint(static_cast(qMin));\n> - static constexpr float max = fixedToFloatingPoint(static_cast(qMax));\n> + static constexpr float min = toFloat(qMin);\n> + static constexpr float max = toFloat(qMax);\n> \n> static_assert(min < max, \"FixedPointQTraits: Minimum must be less than maximum\");\n> \n> @@ -109,7 +72,13 @@ public:\n> static QuantizedType fromFloat(float v)\n> {\n> v = std::clamp(v, min, max);\n> - return floatingToFixedPoint(v);\n> +\n> + /*\n> + * The intermediate cast to int is needed on arm platforms to\n> + * properly cast negative values. See\n> + * https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/\n> + */\n> + return static_cast(static_cast(std::round(v * (1 << F)))) & bitMask;\n> }\n> };\n> \n> \n> -- \n> 2.52.0\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id F1B1BC0DA4\n\tfor ;\n\tThu, 19 Feb 2026 09:07:01 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id AD52362244;\n\tThu, 19 Feb 2026 10:07:01 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 18F026222F\n\tfor ;\n\tThu, 19 Feb 2026 10:07:00 +0100 (CET)","from neptunite.rasen.tech (unknown\n\t[IPv6:2404:7a81:160:2100:3150:3f17:6415:4c60])\n\tby perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id C7D51673;\n\tThu, 19 Feb 2026 10:06:06 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"cnlLm4t+\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1771491967;\n\tbh=dZ+f2ESbKIOEU0WpCwq5cDWDmNR91oMIHeTTQZCjlyk=;\n\th=In-Reply-To:References:Subject:From:Cc:To:Date:From;\n\tb=cnlLm4t+7fm+BcQK2DQ3xMTrFvrfxlhHbfCSoSnCW1wx5IhuTABH6FwOUv9vAcdhp\n\toX0yOo+Jtvc13/wyY4i2nGYINhRTlnIdDT5bgWVVtPV97OvbVTriDua5Yhf8sUIYrY\n\tnI+4d0G8APNErH7N7euNv1mtBP3DaBrWUoRhHyYg=","Content-Type":"text/plain; charset=\"utf-8\"","MIME-Version":"1.0","Content-Transfer-Encoding":"quoted-printable","In-Reply-To":"<20260213-kbingham-quantizers-v7-15-1626b9aaabf1@ideasonboard.com>","References":"<20260213-kbingham-quantizers-v7-0-1626b9aaabf1@ideasonboard.com>\n\t<20260213-kbingham-quantizers-v7-15-1626b9aaabf1@ideasonboard.com>","Subject":"Re: [PATCH v7 15/15] ipa: libipa: fixedpoint: Move float conversion\n\tinline","From":"Paul Elder ","Cc":"Kieran Bingham ,\n\tIsaac Scott ,\n\tLaurent Pinchart ","To":"Kieran Bingham ,\n\tlibcamera-devel@lists.libcamera.org","Date":"Thu, 19 Feb 2026 18:06:54 +0900","Message-ID":"<177149201420.607498.18166300659961304883@neptunite.rasen.tech>","User-Agent":"alot/0.0.0","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]