[PATCH v1] libcamera: libipa: camera_sensor_helper: Use `variant` instead of `union`
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Mon Dec 9 03:28:55 CET 2024
On Thu, Dec 05, 2024 at 09:58:15PM +0200, Laurent Pinchart wrote:
> Hi Barnabás,
>
> Thank you for the patch.
>
> On Thu, Dec 05, 2024 at 12:27:05PM +0000, Barnabás Pőcze wrote:
> > Use an `std::variant` to store the analogue gain instead of a bare union + tag.
>
> Sounds like the right tool for the job.
>
> > Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
> > ---
> > src/ipa/libipa/camera_sensor_helper.cpp | 198 ++++++++----------------
> > src/ipa/libipa/camera_sensor_helper.h | 18 +--
> > 2 files changed, 70 insertions(+), 146 deletions(-)
> >
> > diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
> > index a76e5e75..ac3d712b 100644
> > --- a/src/ipa/libipa/camera_sensor_helper.cpp
> > +++ b/src/ipa/libipa/camera_sensor_helper.cpp
> > @@ -87,21 +87,18 @@ namespace ipa {
> > */
> > uint32_t CameraSensorHelper::gainCode(double gain) const
> > {
> > - const AnalogueGainConstants &k = gainConstants_;
> > + if (auto *l = std::get_if<AnalogueGainLinear>(&gain_)) {
> > + ASSERT(l->m0 == 0 || l->m1 == 0);
> >
> > - switch (gainType_) {
> > - case AnalogueGainLinear:
> > - ASSERT(k.linear.m0 == 0 || k.linear.m1 == 0);
> > -
> > - return (k.linear.c0 - k.linear.c1 * gain) /
> > - (k.linear.m1 * gain - k.linear.m0);
> > -
> > - case AnalogueGainExponential:
> > - ASSERT(k.exp.a != 0 && k.exp.m != 0);
> > -
> > - return std::log2(gain / k.exp.a) / k.exp.m;
> > + return (l->c0 - l->c1 * gain) /
> > + (l->m1 * gain - l->m0);
> > + }
> > + else if (auto *e = std::get_if<AnalogueGainExp>(&gain_)) {
Actually checkstyle.py reports an issue here and in a few other places.
You can keep my Rb tag for v2 after fixing that.
> > + ASSERT(e->a != 0 && e->m != 0);
> >
> > - default:
> > + return std::log2(gain / e->a) / e->m;
> > + }
> > + else {
> > ASSERT(false);
> > return 0;
> > }
> > @@ -119,38 +116,28 @@ uint32_t CameraSensorHelper::gainCode(double gain) const
> > */
> > double CameraSensorHelper::gain(uint32_t gainCode) const
> > {
> > - const AnalogueGainConstants &k = gainConstants_;
> > double gain = static_cast<double>(gainCode);
> >
> > - switch (gainType_) {
> > - case AnalogueGainLinear:
> > - ASSERT(k.linear.m0 == 0 || k.linear.m1 == 0);
> > -
> > - return (k.linear.m0 * gain + k.linear.c0) /
> > - (k.linear.m1 * gain + k.linear.c1);
> > + if (auto *l = std::get_if<AnalogueGainLinear>(&gain_)) {
> > + ASSERT(l->m0 == 0 || l->m1 == 0);
> >
> > - case AnalogueGainExponential:
> > - ASSERT(k.exp.a != 0 && k.exp.m != 0);
> > -
> > - return k.exp.a * std::exp2(k.exp.m * gain);
> > + return (l->m0 * gain + l->c0) /
> > + (l->m1 * gain + l->c1);
> > + }
> > + else if (auto *e = std::get_if<AnalogueGainExp>(&gain_)) {
> > + ASSERT(e->a != 0 && e->m != 0);
> >
> > - default:
> > + return e->a * std::exp2(e->m * gain);
> > + }
> > + else {
> > ASSERT(false);
> > return 0.0;
> > }
> > }
> >
> > /**
> > - * \enum CameraSensorHelper::AnalogueGainType
> > - * \brief The gain calculation modes as defined by the MIPI CCS
> > - *
> > - * Describes the image sensor analogue gain capabilities.
> > - * Two modes are possible, depending on the sensor: Linear and Exponential.
> > - */
> > -
> > -/**
> > - * \var CameraSensorHelper::AnalogueGainLinear
> > - * \brief Gain is computed using linear gain estimation
> > + * \struct CameraSensorHelper::AnalogueGainLinear
> > + * \brief Analogue gain constants for the linear gain model
> > *
> > * The relationship between the integer gain parameter and the resulting gain
> > * multiplier is given by the following equation:
> > @@ -165,11 +152,27 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
> > * The full Gain equation therefore reduces to either:
> > *
> > * \f$gain=\frac{c0}{m1x+c1}\f$ or \f$\frac{m0x+c0}{c1}\f$
> > + *
> > + * \var CameraSensorHelper::AnalogueGainLinear::m0
> > + * \brief Constant used in the linear gain coding/decoding
> > + *
> > + * \note Either m0 or m1 shall be zero.
> > + *
> > + * \var CameraSensorHelper::AnalogueGainLinear::c0
> > + * \brief Constant used in the linear gain coding/decoding
> > + *
> > + * \var CameraSensorHelper::AnalogueGainLinear::m1
> > + * \brief Constant used in the linear gain coding/decoding
> > + *
> > + * \note Either m0 or m1 shall be zero.
> > + *
> > + * \var CameraSensorHelper::AnalogueGainLinear::c1
> > + * \brief Constant used in the linear gain coding/decoding
> > */
> >
> > /**
> > - * \var CameraSensorHelper::AnalogueGainExponential
> > - * \brief Gain is expressed using an exponential model
> > + * \struct CameraSensorHelper::AnalogueGainExp
> > + * \brief Analogue gain constants for the exponential gain model
> > *
> > * The relationship between the integer gain parameter and the resulting gain
> > * multiplier is given by the following equation:
> > @@ -185,54 +188,14 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
> > *
> > * When the gain is expressed in dB, 'a' is equal to 1 and 'm' to
> > * \f$log_{2}{10^{\frac{1}{20}}}\f$.
> > - */
> > -
> > -/**
> > - * \struct CameraSensorHelper::AnalogueGainLinearConstants
> > - * \brief Analogue gain constants for the linear gain model
> > - *
> > - * \var CameraSensorHelper::AnalogueGainLinearConstants::m0
> > - * \brief Constant used in the linear gain coding/decoding
> > - *
> > - * \note Either m0 or m1 shall be zero.
> > - *
> > - * \var CameraSensorHelper::AnalogueGainLinearConstants::c0
> > - * \brief Constant used in the linear gain coding/decoding
> > - *
> > - * \var CameraSensorHelper::AnalogueGainLinearConstants::m1
> > - * \brief Constant used in the linear gain coding/decoding
> > - *
> > - * \note Either m0 or m1 shall be zero.
> > - *
> > - * \var CameraSensorHelper::AnalogueGainLinearConstants::c1
> > - * \brief Constant used in the linear gain coding/decoding
> > - */
> > -
> > -/**
> > - * \struct CameraSensorHelper::AnalogueGainExpConstants
> > - * \brief Analogue gain constants for the exponential gain model
> > *
> > - * \var CameraSensorHelper::AnalogueGainExpConstants::a
> > + * \var CameraSensorHelper::AnalogueGainExp::a
> > * \brief Constant used in the exponential gain coding/decoding
> > *
> > - * \var CameraSensorHelper::AnalogueGainExpConstants::m
> > + * \var CameraSensorHelper::AnalogueGainExp::m
> > * \brief Constant used in the exponential gain coding/decoding
> > */
> >
> > -/**
> > - * \struct CameraSensorHelper::AnalogueGainConstants
> > - * \brief Analogue gain model constants
> > - *
> > - * This union stores the constants used to calculate the analogue gain. The
> > - * CameraSensorHelper::gainType_ variable selects which union member is valid.
> > - *
> > - * \var CameraSensorHelper::AnalogueGainConstants::linear
> > - * \brief Constants for the linear gain model
> > - *
> > - * \var CameraSensorHelper::AnalogueGainConstants::exp
> > - * \brief Constants for the exponential gain model
> > - */
> > -
> > /**
> > * \var CameraSensorHelper::blackLevel_
> > * \brief The black level of the sensor
> > @@ -240,12 +203,7 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
> > */
> >
> > /**
> > - * \var CameraSensorHelper::gainType_
> > - * \brief The analogue gain model type
> > - */
> > -
> > -/**
> > - * \var CameraSensorHelper::gainConstants_
> > + * \var CameraSensorHelper::gain_
> > * \brief The analogue gain parameters used for calculation
> > *
> > * The analogue gain is calculated through a formula, and its parameters are
> > @@ -526,8 +484,7 @@ public:
> > {
> > /* From datasheet: 64 at 10bits. */
> > blackLevel_ = 4096;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 100, 0, 0, 1024 };
> > + gain_ = AnalogueGainLinear{ 100, 0, 0, 1024 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("gc05a2", CameraSensorHelperGc05a2)
> > @@ -539,8 +496,7 @@ public:
> > {
> > /* From datasheet: 64 at 10bits. */
> > blackLevel_ = 4096;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 100, 0, 0, 1024 };
> > + gain_ = AnalogueGainLinear{ 100, 0, 0, 1024 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("gc08a3", CameraSensorHelperGc08a3)
> > @@ -552,8 +508,7 @@ public:
> > {
> > /* From datasheet: 64 at 10bits. */
> > blackLevel_ = 4096;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 0, 512, -1, 512 };
> > + gain_ = AnalogueGainLinear{ 0, 512, -1, 512 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx214", CameraSensorHelperImx214)
> > @@ -565,8 +520,7 @@ public:
> > {
> > /* From datasheet: 64 at 10bits. */
> > blackLevel_ = 4096;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 0, 256, -1, 256 };
> > + gain_ = AnalogueGainLinear{ 0, 256, -1, 256 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx219", CameraSensorHelperImx219)
> > @@ -578,8 +532,7 @@ public:
> > {
> > /* From datasheet: 0x40 at 10bits. */
> > blackLevel_ = 4096;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 0, 512, -1, 512 };
> > + gain_ = AnalogueGainLinear{ 0, 512, -1, 512 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx258", CameraSensorHelperImx258)
> > @@ -591,8 +544,7 @@ public:
> > {
> > /* From datasheet: 0x32 at 10bits. */
> > blackLevel_ = 3200;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 0, 2048, -1, 2048 };
> > + gain_ = AnalogueGainLinear{ 0, 2048, -1, 2048 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx283", CameraSensorHelperImx283)
> > @@ -604,8 +556,7 @@ public:
> > {
> > /* From datasheet: 0xf0 at 12bits. */
> > blackLevel_ = 3840;
> > - gainType_ = AnalogueGainExponential;
> > - gainConstants_.exp = { 1.0, expGainDb(0.3) };
> > + gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx290", CameraSensorHelperImx290)
> > @@ -615,8 +566,7 @@ class CameraSensorHelperImx296 : public CameraSensorHelper
> > public:
> > CameraSensorHelperImx296()
> > {
> > - gainType_ = AnalogueGainExponential;
> > - gainConstants_.exp = { 1.0, expGainDb(0.1) };
> > + gain_ = AnalogueGainExp{ 1.0, expGainDb(0.1) };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx296", CameraSensorHelperImx296)
> > @@ -633,8 +583,7 @@ public:
> > {
> > /* From datasheet: 0x32 at 10bits. */
> > blackLevel_ = 3200;
> > - gainType_ = AnalogueGainExponential;
> > - gainConstants_.exp = { 1.0, expGainDb(0.3) };
> > + gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx335", CameraSensorHelperImx335)
> > @@ -644,8 +593,7 @@ class CameraSensorHelperImx415 : public CameraSensorHelper
> > public:
> > CameraSensorHelperImx415()
> > {
> > - gainType_ = AnalogueGainExponential;
> > - gainConstants_.exp = { 1.0, expGainDb(0.3) };
> > + gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx415", CameraSensorHelperImx415)
> > @@ -660,8 +608,7 @@ class CameraSensorHelperImx477 : public CameraSensorHelper
> > public:
> > CameraSensorHelperImx477()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 0, 1024, -1, 1024 };
> > + gain_ = AnalogueGainLinear{ 0, 1024, -1, 1024 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("imx477", CameraSensorHelperImx477)
> > @@ -675,8 +622,7 @@ public:
> > * The Sensor Manual doesn't appear to document the gain model.
> > * This has been validated with some empirical testing only.
> > */
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov2685", CameraSensorHelperOv2685)
> > @@ -686,8 +632,7 @@ class CameraSensorHelperOv2740 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv2740()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov2740", CameraSensorHelperOv2740)
> > @@ -699,8 +644,7 @@ public:
> > {
> > /* From datasheet: 0x40 at 12bits. */
> > blackLevel_ = 1024;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov4689", CameraSensorHelperOv4689)
> > @@ -712,8 +656,7 @@ public:
> > {
> > /* From datasheet: 0x10 at 10bits. */
> > blackLevel_ = 1024;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 16 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 16 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov5640", CameraSensorHelperOv5640)
> > @@ -723,8 +666,7 @@ class CameraSensorHelperOv5647 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv5647()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 16 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 16 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov5647", CameraSensorHelperOv5647)
> > @@ -734,8 +676,7 @@ class CameraSensorHelperOv5670 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv5670()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov5670", CameraSensorHelperOv5670)
> > @@ -747,8 +688,7 @@ public:
> > {
> > /* From Linux kernel driver: 0x40 at 10bits. */
> > blackLevel_ = 4096;
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov5675", CameraSensorHelperOv5675)
> > @@ -758,8 +698,7 @@ class CameraSensorHelperOv5693 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv5693()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 16 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 16 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov5693", CameraSensorHelperOv5693)
> > @@ -769,8 +708,7 @@ class CameraSensorHelperOv64a40 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv64a40()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov64a40", CameraSensorHelperOv64a40)
> > @@ -780,15 +718,13 @@ class CameraSensorHelperOv8858 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv8858()
> > {
> > - gainType_ = AnalogueGainLinear;
> > -
> > /*
> > * \todo Validate the selected 1/128 step value as it differs
> > * from what the sensor manual describes.
> > *
> > * See: https://patchwork.linuxtv.org/project/linux-media/patch/20221106171129.166892-2-nicholas@rothemail.net/#142267
> > */
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov8858", CameraSensorHelperOv8858)
> > @@ -798,8 +734,7 @@ class CameraSensorHelperOv8865 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv8865()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov8865", CameraSensorHelperOv8865)
> > @@ -809,8 +744,7 @@ class CameraSensorHelperOv13858 : public CameraSensorHelper
> > public:
> > CameraSensorHelperOv13858()
> > {
> > - gainType_ = AnalogueGainLinear;
> > - gainConstants_.linear = { 1, 0, 0, 128 };
> > + gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> > }
> > };
> > REGISTER_CAMERA_SENSOR_HELPER("ov13858", CameraSensorHelperOv13858)
> > diff --git a/src/ipa/libipa/camera_sensor_helper.h b/src/ipa/libipa/camera_sensor_helper.h
> > index 75868205..a9300a64 100644
> > --- a/src/ipa/libipa/camera_sensor_helper.h
> > +++ b/src/ipa/libipa/camera_sensor_helper.h
> > @@ -11,6 +11,7 @@
> > #include <optional>
> > #include <stdint.h>
> > #include <string>
> > +#include <variant>
> > #include <vector>
> >
> > #include <libcamera/base/class.h>
> > @@ -30,31 +31,20 @@ public:
> > virtual double gain(uint32_t gainCode) const;
> >
> > protected:
> > - enum AnalogueGainType {
> > - AnalogueGainLinear,
> > - AnalogueGainExponential,
> > - };
> > -
> > - struct AnalogueGainLinearConstants {
> > + struct AnalogueGainLinear {
> > int16_t m0;
> > int16_t c0;
> > int16_t m1;
> > int16_t c1;
> > };
> >
> > - struct AnalogueGainExpConstants {
> > + struct AnalogueGainExp {
> > double a;
> > double m;
> > };
> >
> > - union AnalogueGainConstants {
> > - AnalogueGainLinearConstants linear;
> > - AnalogueGainExpConstants exp;
> > - };
> > -
> > std::optional<int16_t> blackLevel_;
> > - AnalogueGainType gainType_;
> > - AnalogueGainConstants gainConstants_;
> > + std::variant<std::monostate, AnalogueGainLinear, AnalogueGainExp> gain_;
> >
> > private:
> > LIBCAMERA_DISABLE_COPY_AND_MOVE(CameraSensorHelper)
--
Regards,
Laurent Pinchart
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