5 files changed, 75 insertions, 7 deletions
diff --git a/src/libcamera/control_ids.cpp.in b/src/libcamera/control_ids.cpp.in
index afe9e2c9..65668d48 100644
--- a/src/libcamera/control_ids.cpp.in
+++ b/src/libcamera/control_ids.cpp.in
@@ -89,9 +89,9 @@ extern const std::map<std::string, {{ctrl.type}}> {{ctrl.name}}NameValueMap = {
 	{ "{{enum.name}}", {{enum.name}} },
 {%- endfor %}
 };
-extern const Control<{{ctrl.type}}> {{ctrl.name}}({{ctrl.name|snake_case|upper}}, "{{ctrl.name}}", "{{vendor}}", {{ctrl.name}}NameValueMap);
+extern const Control<{{ctrl.type}}> {{ctrl.name}}({{ctrl.name|snake_case|upper}}, "{{ctrl.name}}", "{{vendor}}", {{ctrl.direction}}, {{ctrl.name}}NameValueMap);
 {% else -%}
-extern const Control<{{ctrl.type}}> {{ctrl.name}}({{ctrl.name|snake_case|upper}}, "{{ctrl.name}}", "{{vendor}}");
+extern const Control<{{ctrl.type}}> {{ctrl.name}}({{ctrl.name|snake_case|upper}}, "{{ctrl.name}}", "{{vendor}}", {{ctrl.direction}});
 {% endif -%}
 {%- endfor %}
 
diff --git a/src/libcamera/control_serializer.cpp b/src/libcamera/control_serializer.cpp
index 0a5e8220..17834648 100644
--- a/src/libcamera/control_serializer.cpp
+++ b/src/libcamera/control_serializer.cpp
@@ -281,6 +281,7 @@ int ControlSerializer::serialize(const ControlInfoMap &infoMap,
 		entry.id = id->id();
 		entry.type = id->type();
 		entry.offset = values.offset();
+		entry.direction = static_cast<ControlId::DirectionFlags::Type>(id->direction());
 		entries.write(&entry);
 
 		store(info, values);
@@ -493,12 +494,17 @@ ControlInfoMap ControlSerializer::deserialize<ControlInfoMap>(ByteStreamBuffer &
 
 		/* If we're using a local id map, populate it. */
 		if (localIdMap) {
+			ControlId::DirectionFlags flags{
+				static_cast<ControlId::Direction>(entry->direction)
+			};
+
 			/**
 			 * \todo Find a way to preserve the control name for
 			 * debugging purpose.
 			 */
 			controlIds_.emplace_back(std::make_unique<ControlId>(entry->id,
-									     "", "local", type));
+									     "", "local", type,
+									     flags));
 			(*localIdMap)[entry->id] = controlIds_.back().get();
 		}
 
diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
index 65eeef2d..70f6f609 100644
--- a/src/libcamera/controls.cpp
+++ b/src/libcamera/controls.cpp
@@ -412,15 +412,16 @@ void ControlValue::reserve(ControlType type, bool isArray, std::size_t numElemen
  * \param[in] name The control name
  * \param[in] vendor The vendor name
  * \param[in] type The control data type
+ * \param[in] direction The direction of the control, if it can be used in Controls or Metadata
  * \param[in] size The size of the array control, or 0 if scalar control
  * \param[in] enumStrMap The map from enum names to values (optional)
  */
 ControlId::ControlId(unsigned int id, const std::string &name,
 		     const std::string &vendor, ControlType type,
-		     std::size_t size,
+		     DirectionFlags direction, std::size_t size,
 		     const std::map<std::string, int32_t> &enumStrMap)
-	: id_(id), name_(name), vendor_(vendor), type_(type), size_(size),
-	  enumStrMap_(enumStrMap)
+	: id_(id), name_(name), vendor_(vendor), type_(type),
+	  direction_(direction), size_(size), enumStrMap_(enumStrMap)
 {
 	for (const auto &pair : enumStrMap_)
 		reverseMap_[pair.second] = pair.first;
@@ -451,6 +452,37 @@ ControlId::ControlId(unsigned int id, const std::string &name,
  */
 
 /**
+ * \fn DirectionFlags ControlId::direction() const
+ * \brief Return the direction that the control can be used in
+ *
+ * This is similar to \sa isInput() and \sa isOutput(), but returns the flags
+ * direction instead of booleans for each direction.
+ *
+ * \return The direction flags corresponding to if the control can be used as
+ * an input control or as output metadata
+ */
+
+/**
+ * \fn bool ControlId::isInput() const
+ * \brief Determine if the control is available to be used as an input control
+ *
+ * Controls can be used either as input in controls, or as output in metadata.
+ * This function checks if the control is allowed to be used as the former.
+ *
+ * \return True if the control can be used as an input control, false otherwise
+ */
+
+/**
+ * \fn bool ControlId::isOutput() const
+ * \brief Determine if the control is available to be used in output metadata
+ *
+ * Controls can be used either as input in controls, or as output in metadata.
+ * This function checks if the control is allowed to be used as the latter.
+ *
+ * \return True if the control can be returned in output metadata, false otherwise
+ */
+
+/**
  * \fn bool ControlId::isArray() const
  * \brief Determine if the control is an array control
  * \return True if the control is an array control, false otherwise
@@ -488,6 +520,22 @@ ControlId::ControlId(unsigned int id, const std::string &name,
  */
 
 /**
+ * \enum ControlId::Direction
+ * \brief The direction the control is capable of being passed from/to
+ *
+ * \var ControlId::Direction::In
+ * \brief The control can be passed as input in controls
+ *
+ * \var ControlId::Direction::Out
+ * \brief The control can be returned as output in metadata
+ */
+
+/**
+ * \typedef ControlId::DirectionFlags
+ * \brief A wrapper for ControlId::Direction so that it can be used as flags
+ */
+
+/**
  * \class Control
  * \brief Describe a control and its intrinsic properties
  *
@@ -520,6 +568,8 @@ ControlId::ControlId(unsigned int id, const std::string &name,
  * \param[in] id The control numerical ID
  * \param[in] name The control name
  * \param[in] vendor The vendor name
+ * \param[in] direction The direction of the control, if it can be used in
+ * Controls or Metadata
  * \param[in] enumStrMap The map from enum names to values (optional)
  *
  * The control data type is automatically deduced from the template type T.
diff --git a/src/libcamera/ipa_controls.cpp b/src/libcamera/ipa_controls.cpp
index 9420c889..12d92ebe 100644
--- a/src/libcamera/ipa_controls.cpp
+++ b/src/libcamera/ipa_controls.cpp
@@ -220,6 +220,10 @@ static_assert(sizeof(ipa_control_value_entry) == 16,
  * \var ipa_control_info_entry::offset
  * The offset in bytes from the beginning of the data section to the control
  * info data (shall be a multiple of 8 bytes)
+ * \var ipa_control_info_entry::direction
+ * The directions in which the control is allowed to be sent. This is a flags
+ * value, where 0x1 signifies input (as controls), and 0x2 signifies output (as
+ * metadata). \sa ControlId::Direction
  * \var ipa_control_info_entry::padding
  * Padding bytes (shall be set to 0)
  */
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 664b74af..2f65a43a 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -565,7 +565,15 @@ std::unique_ptr<ControlId> V4L2Device::v4l2ControlId(const v4l2_query_ext_ctrl &
 	const std::string name(static_cast<const char *>(ctrl.name), len);
 	const ControlType type = v4l2CtrlType(ctrl.type);
 
-	return std::make_unique<ControlId>(ctrl.id, name, "v4l2", type);
+	ControlId::DirectionFlags flags;
+	if (ctrl.flags & V4L2_CTRL_FLAG_READ_ONLY)
+		flags = ControlId::Direction::Out;
+	else if (ctrl.flags & V4L2_CTRL_FLAG_WRITE_ONLY)
+		flags = ControlId::Direction::In;
+	else
+		flags = ControlId::Direction::In | ControlId::Direction::Out;
+
+	return std::make_unique<ControlId>(ctrl.id, name, "v4l2", type, flags);
 }
 
 /**