libcamera: v4l2_subdevice: Replace ImageFormats with a map

Replace the V4L2Subdevice usage of the ImageFormats class with a
std::map and the utils::map_keys() helper.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/v4l2_subdevice.cpp

@@ -217,6 +217,11 @@ uint8_t V4L2SubdeviceFormat::bitsPerPixel() const
  * any device left open will be closed, and any resources released.
  */
 
+/**
+ * \typedef V4L2Subdevice::Formats
+ * \brief A map of supported media bus formats to frame sizes
+ */
+
 /**
  * \enum V4L2Subdevice::Whence
  * \brief Specify the type of format for getFormat() and setFormat() operations
@@ -340,9 +345,9 @@ int V4L2Subdevice::setSelection(unsigned int pad, unsigned int target,
  *
  * \return A list of the supported device formats
  */
-ImageFormats V4L2Subdevice::formats(unsigned int pad)
+V4L2Subdevice::Formats V4L2Subdevice::formats(unsigned int pad)
 {
-	ImageFormats formats;
+	Formats formats;
 
 	if (pad >= entity_->pads().size()) {
 		LOG(V4L2, Error) << "Invalid pad: " << pad;
@@ -354,7 +359,8 @@ ImageFormats V4L2Subdevice::formats(unsigned int pad)
 		if (sizes.empty())
 			return {};
 
-		if (formats.addFormat(code, sizes)) {
+		const auto inserted = formats.insert({ code, sizes });
+		if (!inserted.second) {
 			LOG(V4L2, Error)
 				<< "Could not add sizes for media bus code "
 				<< code << " on pad " << pad;