[libcamera-devel] [PATCH v1] gstreamer: Added virtual functions needed to support request pads

[Vedant Paranjape]

Using request pads needs virtual functions to create new request pads and
release the allocated pads.

It defines the functions gst_libcamera_src_request_new_pad() and
gst_libcamera_src_release_pad() which handle, creating and releasing
request pads. It also assigned these functions to their callback
handlers in GstLibcameraSrcClass.

This doesn't enable request pad support in gstreamer element. This is
one of the series of changes needed to make it work.

Signed-off-by: Vedant Paranjape <vedantparanjape160201 at gmail.com>
---
 src/gstreamer/gstlibcamerasrc.cpp | 53 +++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
index ccc61590..f0a4fbf0 100644
--- a/src/gstreamer/gstlibcamerasrc.cpp
+++ b/src/gstreamer/gstlibcamerasrc.cpp
@@ -640,6 +640,57 @@ gst_libcamera_src_init(GstLibcameraSrc *self)
 	self->state = state;
 }
 
+static GstPad*
+gst_libcamera_src_request_new_pad(GstElement *element, GstPadTemplate *templ,
+					const gchar *name, [[maybe_unused]] const GstCaps *caps)
+{
+	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
+	g_autoptr(GstPad) pad = NULL;
+
+	pad = gst_pad_new_from_template(templ, name);
+	if (G_IS_INITIALLY_UNOWNED (pad))
+	{
+		g_object_ref_sink(pad);
+	}
+	
+	{
+		GLibLocker lock(GST_OBJECT(self->state));
+		self->state->srcpads_.push_back((GstPad*)g_object_ref(&pad));
+	}
+
+	if (!gst_element_add_pad(element, pad))
+	{
+		GST_ELEMENT_ERROR (element, STREAM, FAILED,
+			("Internal data stream error."), ("Could not add pad to element"));
+		{
+			GLibLocker lock(GST_OBJECT(self->state));
+			self->state->srcpads_.pop_back();
+		}
+		return NULL;		
+	}
+
+	return (GstPad*)g_steal_pointer(&pad);
+}
+
+static void
+gst_libcamera_src_release_pad(GstElement *element, GstPad *pad)
+{
+	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
+	
+	GST_DEBUG_OBJECT (self, "Pad %" GST_PTR_FORMAT " being released", pad);
+
+	{
+		GLibLocker lock(GST_OBJECT(self->state));
+		auto iterator = std::find(self->state->srcpads_.begin(), self->state->srcpads_.end(), pad);
+		if (iterator != self->state->srcpads_.end())
+		{
+			g_object_unref(self->state->srcpads_[std::distance(self->state->srcpads_.begin(), iterator)]);
+			self->state->srcpads_.erase(iterator);
+		}
+	}
+	gst_element_remove_pad(element, pad);
+}
+
 static void
 gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
 {
@@ -650,6 +701,8 @@ gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
 	object_class->get_property = gst_libcamera_src_get_property;
 	object_class->finalize = gst_libcamera_src_finalize;
 
+	element_class->request_new_pad = gst_libcamera_src_request_new_pad;
+	element_class->release_pad = gst_libcamera_src_release_pad;
 	element_class->change_state = gst_libcamera_src_change_state;
 
 	gst_element_class_set_metadata(element_class,
-- 
2.25.1