libcamera: formats: Add ImageFormats

Add a new class to hold format information for V4L2 devices and
subdevices. The object describes the relationship between either pixel
formats (V4L2 devices) or media bus codes (V4L2 subdevice) and a list of
image sizes which can be produced with that format.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/formats.cpp

@@ -24,4 +24,92 @@ namespace libcamera {
  * resolutions represented by SizeRange items.
  */
 
+/**
+ * \class ImageFormats
+ * \brief Describe V4L2Device and V4L2SubDevice image formats
+ *
+ * This class stores a list of image formats, each associated with a
+ * corresponding set of image sizes. It is used to describe the formats and
+ * sizes supported by a V4L2Device or V4L2Subdevice.
+ *
+ * Formats are stored as an integer. When used for a V4L2Device, the image
+ * formats are fourcc pixel formats. When used for a V4L2Subdevice they are
+ * media bus codes. Both are defined by the V4L2 specification.
+ *
+ * Sizes are stored as a list of SizeRange.
+ */
+
+/**
+ * \brief Add a format and corresponding sizes to the description
+ * \param[in] format Pixel format or media bus code to describe
+ * \param[in] sizes List of supported size ranges for the format
+ *
+ * \return 0 on success or a negative error code otherwise
+ * \retval -EEXIST The format is already described
+ */
+int ImageFormats::addFormat(unsigned int format, const std::vector<SizeRange> &sizes)
+{
+	if (data_.find(format) != data_.end())
+		return -EEXIST;
+
+	data_[format] = sizes;
+
+	return 0;
+}
+
+/**
+ * \brief Check if the list of devices supported formats is empty
+ * \return True if the list of supported formats is empty
+ */
+bool ImageFormats::isEmpty() const
+{
+	return data_.empty();
+}
+
+/**
+ * \brief Retrieve a list of all supported image formats
+ * \return List of pixel formats or media bus codes
+ */
+std::vector<unsigned int> ImageFormats::formats() const
+{
+	std::vector<unsigned int> formats;
+	formats.reserve(data_.size());
+
+	/* \todo: Should this be cached instead of computed each time? */
+	for (auto const &it : data_)
+		formats.push_back(it.first);
+
+	return formats;
+}
+
+/**
+ * \brief Retrieve all sizes for a specific format
+ * \param[in] format The pixel format or mbus code
+ *
+ * Retrieve all size ranges for a specific format. For V4L2Device \a format is a
+ * pixel format while for a V4L2Subdevice \a format is a media bus code.
+ *
+ * \return The list of image sizes supported for \a format, or an empty list if
+ * the format is not supported
+ */
+const std::vector<SizeRange> &ImageFormats::sizes(unsigned int format) const
+{
+	static std::vector<SizeRange> empty;
+
+	auto const &it = data_.find(format);
+	if (it == data_.end())
+		return empty;
+
+	return it->second;
+}
+
+/**
+ * \brief Retrieve the map that associates formats to image sizes
+ * \return The map that associates formats to image sizes
+ */
+const std::map<unsigned int, std::vector<SizeRange>> &ImageFormats::data() const
+{
+	return data_;
+}
+
 } /* namespace libcamera */

src/libcamera/include/formats.h

@@ -17,6 +17,20 @@ namespace libcamera {
 
 typedef std::map<unsigned int, std::vector<SizeRange>> FormatEnum;
 
+class ImageFormats
+{
+public:
+	int addFormat(unsigned int format, const std::vector<SizeRange> &sizes);
+
+	bool isEmpty() const;
+	std::vector<unsigned int> formats() const;
+	const std::vector<SizeRange> &sizes(unsigned int format) const;
+	const std::map<unsigned int, std::vector<SizeRange>> &data() const;
+
+private:
+	std::map<unsigned int, std::vector<SizeRange>> data_;
+};
+
 } /* namespace libcamera */
 
 #endif /* __LIBCAMERA_FORMATS_H__ */