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diff --git a/src/ipa/raspberrypi/md_parser.hpp b/src/ipa/raspberrypi/md_parser.hpp
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+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi (Trading) Limited
+ *
+ * md_parser.hpp - image sensor metadata parser interface
+ */
+#pragma once
+
+#include <stdint.h>
+
+/* Camera metadata parser class. Usage as shown below.
+
+Setup:
+
+Usually the metadata parser will be made as part of the CamHelper class so
+application code doesn't have to worry which to kind to instantiate. But for
+the sake of example let's suppose we're parsing imx219 metadata.
+
+MdParser *parser = new MdParserImx219();  // for example
+parser->SetBitsPerPixel(bpp);
+parser->SetLineLengthBytes(pitch);
+parser->SetNumLines(2);
+
+Note 1: if you don't know how many lines there are, you can use SetBufferSize
+instead to limit the total buffer size.
+
+Note 2: if you don't know the line length, you can leave the line length unset
+(or set to zero) and the parser will hunt for the line start instead. In this
+case SetBufferSize *must* be used so that the parser won't run off the end of
+the buffer.
+
+Then on every frame:
+
+if (parser->Parse(data) != MdParser::OK)
+    much badness;
+unsigned int exposure_lines, gain_code
+if (parser->GetExposureLines(exposure_lines) != MdParser::OK)
+    exposure was not found;
+if (parser->GetGainCode(parser, gain_code) != MdParser::OK)
+    gain code was not found;
+
+(Note that the CamHelper class converts to/from exposure lines and time,
+and gain_code / actual gain.)
+
+If you suspect your embedded data may have changed its layout, change any line
+lengths, number of lines, bits per pixel etc. that are different, and
+then:
+
+parser->Reset();
+
+before calling Parse again. */
+
+namespace RPi {
+
+// Abstract base class from which other metadata parsers are derived.
+
+class MdParser
+{
+public:
+	// Parser status codes:
+	// OK       - success
+	// NOTFOUND - value such as exposure or gain was not found
+	// ERROR    - all other errors
+	enum Status {
+		OK = 0,
+		NOTFOUND = 1,
+		ERROR = 2
+	};
+	MdParser() : reset_(true) {}
+	virtual ~MdParser() {}
+	void Reset() { reset_ = true; }
+	void SetBitsPerPixel(int bpp) { bits_per_pixel_ = bpp; }
+	void SetNumLines(unsigned int num_lines) { num_lines_ = num_lines; }
+	void SetLineLengthBytes(unsigned int num_bytes)
+	{
+		line_length_bytes_ = num_bytes;
+	}
+	void SetBufferSize(unsigned int num_bytes)
+	{
+		buffer_size_bytes_ = num_bytes;
+	}
+	virtual Status Parse(void *data) = 0;
+	virtual Status GetExposureLines(unsigned int &lines) = 0;
+	virtual Status GetGainCode(unsigned int &gain_code) = 0;
+
+protected:
+	bool reset_;
+	int bits_per_pixel_;
+	unsigned int num_lines_;
+	unsigned int line_length_bytes_;
+	unsigned int buffer_size_bytes_;
+};
+
+// This isn't a full implementation of a metadata parser for SMIA sensors,
+// however, it does provide the findRegs method which will prove useful and make
+// it easier to implement parsers for other SMIA-like sensors (see
+// md_parser_imx219.cpp for an example).
+
+class MdParserSmia : public MdParser
+{
+public:
+	MdParserSmia() : MdParser() {}
+
+protected:
+	// Note that error codes > 0 are regarded as non-fatal; codes < 0
+	// indicate a bad data buffer. Status codes are:
+	// PARSE_OK     - found all registers, much happiness
+	// MISSING_REGS - some registers found; should this be a hard error?
+	// The remaining codes are all hard errors.
+	enum ParseStatus {
+		PARSE_OK      =  0,
+		MISSING_REGS  =  1,
+		NO_LINE_START = -1,
+		ILLEGAL_TAG   = -2,
+		BAD_DUMMY     = -3,
+		BAD_LINE_END  = -4,
+		BAD_PADDING   = -5
+	};
+	ParseStatus findRegs(unsigned char *data, uint32_t regs[],
+			     int offsets[], unsigned int num_regs);
+};
+
+} // namespace RPi