libcamera: converter: Add function to query crop bounds

The inputCropBounds_ member of the V4L2M2MConverter::Stream class is
only initialized after a V4L2M2MConverter::configure() call, when the
streams are initialized.

However, the converter has crop limits that do not depend on the
configured Streams, and which are currently not accessible from the
class interface.

Add a new inputCropBounds() function to the V4L2M2MConverter class
that allows to retrieve the converter crop limits before any stream
is configured.

This is particularly useful for pipelines to initialize controls and
properties and to implement validation before the Camera gets
configured.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

include/libcamera/internal/converter.h

@@ -66,6 +66,7 @@ public:
 				 const std::map<const Stream *, FrameBuffer *> &outputs) = 0;
 
 	virtual int setInputCrop(const Stream *stream, Rectangle *rect) = 0;
+	virtual std::pair<Rectangle, Rectangle> inputCropBounds() = 0;
 	virtual std::pair<Rectangle, Rectangle> inputCropBounds(const Stream *stream) = 0;
 
 	Signal<FrameBuffer *> inputBufferReady;

include/libcamera/internal/converter/converter_v4l2_m2m.h

@@ -60,6 +60,7 @@ public:
 			 const std::map<const Stream *, FrameBuffer *> &outputs) override;
 
 	int setInputCrop(const Stream *stream, Rectangle *rect) override;
+	std::pair<Rectangle, Rectangle> inputCropBounds() override { return inputCropBounds_; }
 	std::pair<Rectangle, Rectangle> inputCropBounds(const Stream *stream) override;
 
 private:
@@ -106,6 +107,7 @@ private:
 
 	std::map<const Stream *, std::unique_ptr<V4L2M2MStream>> streams_;
 	std::map<FrameBuffer *, unsigned int> queue_;
+	std::pair<Rectangle, Rectangle> inputCropBounds_;
 };
 
 } /* namespace libcamera */

src/libcamera/converter.cpp

@@ -185,6 +185,16 @@ Converter::~Converter()
 
 /**
  * \fn Converter::inputCropBounds()
+ * \brief Retrieve the crop bounds of the converter
+ *
+ * Retrieve the minimum and maximum crop bounds of the converter. This can be
+ * used to query the crop bounds before configuring a stream.
+ *
+ * \return A pair containing the minimum and maximum crop bound in that order
+ */
+
+/**
+ * \fn Converter::inputCropBounds(const Stream *stream)
  * \brief Retrieve the crop bounds for \a stream
  * \param[in] stream The output stream
  *
@@ -195,6 +205,9 @@ Converter::~Converter()
  * this function should be called after the \a stream has been configured using
  * configure().
  *
+ * When called with an unconfigured \a stream, this function returns a pair of
+ * null rectangles.
+ *
  * \return A pair containing the minimum and maximum crop bound in that order
  */
 

src/libcamera/converter/converter_v4l2_m2m.cpp

@@ -273,10 +273,9 @@ V4L2M2MConverter::V4L2M2MConverter(MediaDevice *media)
 		return;
 	}
 
-	Rectangle minCrop;
-	Rectangle maxCrop;
-	ret = getCropBounds(m2m_->output(), minCrop, maxCrop);
-	if (!ret && minCrop != maxCrop) {
+	ret = getCropBounds(m2m_->output(), inputCropBounds_.first,
+			    inputCropBounds_.second);
+	if (!ret && inputCropBounds_.first != inputCropBounds_.second) {
 		features_ |= Feature::InputCrop;
 
 		LOG(Converter, Info)
@@ -469,14 +468,21 @@ int V4L2M2MConverter::setInputCrop(const Stream *stream, Rectangle *rect)
 }
 
 /**
- * \copydoc libcamera::Converter::inputCropBounds
+ * \fn libcamera::V4L2M2MConverter::inputCropBounds()
+ * \copydoc libcamera::Converter::inputCropBounds()
+ */
+
+/**
+ * \copydoc libcamera::Converter::inputCropBounds(const Stream *stream)
  */
 std::pair<Rectangle, Rectangle>
 V4L2M2MConverter::inputCropBounds(const Stream *stream)
 {
 	auto iter = streams_.find(stream);
-	if (iter == streams_.end())
+	if (iter == streams_.end()) {
+		LOG(Converter, Error) << "Invalid output stream";
 		return {};
+	}
 
 	return iter->second->inputCropBounds();
 }