[PATCH v1] libcamera: rpi: Add support for IMX258

[Isaac Scott]

Add support for the IMX258 camera. This patch adds a minimal cam_helper
implementation that allows the IMX258 sensor to be listed by cam, and
subsequently be used remotely in tools such as Camshark.

Based on the implementation of the IMX290's camera helper, adjusted to
use the equation listed in the IMX258 datasheet used to calculate
analogue gain.

Signed-off-by: Isaac Scott <isaac.scott at ideasonboard.com>
---
 src/ipa/rpi/cam_helper/cam_helper_imx258.cpp | 60 ++++++++++++++++++++
 src/ipa/rpi/cam_helper/meson.build           |  1 +
 2 files changed, 61 insertions(+)
 create mode 100644 src/ipa/rpi/cam_helper/cam_helper_imx258.cpp

diff --git a/src/ipa/rpi/cam_helper/cam_helper_imx258.cpp b/src/ipa/rpi/cam_helper/cam_helper_imx258.cpp
new file mode 100644
index 00000000..12c0332a
--- /dev/null
+++ b/src/ipa/rpi/cam_helper/cam_helper_imx258.cpp
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2024 Ideas On Board Oy
+ *
+ * camera helper for imx258 sensor
+ * based on Raspberry Pi's imx290 helper
+ */
+
+#include <cmath>
+
+#include "cam_helper.h"
+
+using namespace RPiController;
+
+class CamHelperImx258 : public CamHelper
+{
+public:
+	CamHelperImx258();
+	uint32_t gainCode(double gain) const override;
+	double gain(uint32_t gainCode) const override;
+	void getDelays(int &exposureDelay, int &gainDelay,
+		       int &vblankDelay, int &hblankDelay) const override;
+private:
+	/*
+	 * Smallest difference between the frame length and integration time,
+	 * in units of lines.
+	 */
+	static constexpr int frameIntegrationDiff = 2;
+};
+
+CamHelperImx258::CamHelperImx258()
+	: CamHelper({}, frameIntegrationDiff)
+{
+}
+
+uint32_t CamHelperImx258::gainCode(double gain) const
+{
+	return static_cast<uint32_t>(512 - 512 / gain);
+}
+
+double CamHelperImx258::gain(uint32_t gainCode) const
+{
+	return 512.0 / (512.0 - gainCode);
+}
+
+void CamHelperImx258::getDelays(int &exposureDelay, int &gainDelay,
+				int &vblankDelay, int &hblankDelay) const
+{
+	exposureDelay = 2;
+	gainDelay = 2;
+	vblankDelay = 2;
+	hblankDelay = 2;
+}
+
+static CamHelper *create()
+{
+	return new CamHelperImx258();
+}
+
+static RegisterCamHelper reg("imx258", &create);
diff --git a/src/ipa/rpi/cam_helper/meson.build b/src/ipa/rpi/cam_helper/meson.build
index 03e88fe0..a8245e42 100644
--- a/src/ipa/rpi/cam_helper/meson.build
+++ b/src/ipa/rpi/cam_helper/meson.build
@@ -4,6 +4,7 @@ rpi_ipa_cam_helper_sources = files([
     'cam_helper.cpp',
     'cam_helper_ov5647.cpp',
     'cam_helper_imx219.cpp',
+    'cam_helper_imx258.cpp',
     'cam_helper_imx283.cpp',
     'cam_helper_imx290.cpp',
     'cam_helper_imx296.cpp',
-- 
2.43.0