gst: Add pads to the source

This simply adds the boiler plate for pads on the source element. The
design is that we have one pad, called "src", that will always be
present, and then more pads can be requested prior in READY or less
state. Initially pads have one property "stream-role" that let you
decide which role this pad will have.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/gstreamer/gstlibcamerapad.cpp

@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * gstlibcamerapad.cpp - GStreamer Capture Pad
+ */
+
+#include "gstlibcamerapad.h"
+
+#include <libcamera/stream.h>
+
+#include "gstlibcamera-utils.h"
+
+using namespace libcamera;
+
+struct _GstLibcameraPad {
+	GstPad parent;
+	StreamRole role;
+};
+
+enum {
+	PROP_0,
+	PROP_STREAM_ROLE
+};
+
+G_DEFINE_TYPE(GstLibcameraPad, gst_libcamera_pad, GST_TYPE_PAD);
+
+static void
+gst_libcamera_pad_set_property(GObject *object, guint prop_id,
+			       const GValue *value, GParamSpec *pspec)
+{
+	auto *self = GST_LIBCAMERA_PAD(object);
+	GLibLocker lock(GST_OBJECT(self));
+
+	switch (prop_id) {
+	case PROP_STREAM_ROLE:
+		self->role = (StreamRole)g_value_get_enum(value);
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
+		break;
+	}
+}
+
+static void
+gst_libcamera_pad_get_property(GObject *object, guint prop_id, GValue *value,
+			       GParamSpec *pspec)
+{
+	auto *self = GST_LIBCAMERA_PAD(object);
+	GLibLocker lock(GST_OBJECT(self));
+
+	switch (prop_id) {
+	case PROP_STREAM_ROLE:
+		g_value_set_enum(value, self->role);
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
+		break;
+	}
+}
+
+static void
+gst_libcamera_pad_init(GstLibcameraPad *self)
+{
+}
+
+static GType
+gst_libcamera_stream_role_get_type(void)
+{
+	static GType type = 0;
+	static const GEnumValue values[] = {
+		{ StillCapture, "libcamera::StillCapture", "still-capture" },
+		{ VideoRecording, "libcamera::VideoRecording", "video-recording" },
+		{ Viewfinder, "libcamera::Viewfinder", "view-finder" },
+		{ 0, NULL, NULL }
+	};
+
+	if (!type)
+		type = g_enum_register_static("GstLibcameraStreamRole", values);
+
+	return type;
+}
+
+static void
+gst_libcamera_pad_class_init(GstLibcameraPadClass *klass)
+{
+	auto *object_class = G_OBJECT_CLASS(klass);
+
+	object_class->set_property = gst_libcamera_pad_set_property;
+	object_class->get_property = gst_libcamera_pad_get_property;
+
+	auto *spec = g_param_spec_enum("stream-role", "Stream Role",
+				       "The selected stream role",
+				       gst_libcamera_stream_role_get_type(),
+				       VideoRecording,
+				       (GParamFlags)(GST_PARAM_MUTABLE_READY
+					             | G_PARAM_CONSTRUCT
+						     | G_PARAM_READWRITE
+						     | G_PARAM_STATIC_STRINGS));
+	g_object_class_install_property(object_class, PROP_STREAM_ROLE, spec);
+}

src/gstreamer/gstlibcamerapad.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * gstlibcamerapad.h - GStreamer Capture Element
+ */
+
+#include <gst/gst.h>
+
+#ifndef __GST_LIBCAMERA_PAD_H__
+#define __GST_LIBCAMERA_PAD_H__
+
+#define GST_TYPE_LIBCAMERA_PAD gst_libcamera_pad_get_type()
+G_DECLARE_FINAL_TYPE(GstLibcameraPad, gst_libcamera_pad,
+		     GST_LIBCAMERA, PAD, GstPad)
+
+
+#endif /* __GST_LIBCAMERA_PAD_H__ */

src/gstreamer/gstlibcamerasrc.cpp

@@ -8,12 +8,26 @@
 
 #include "gstlibcamerasrc.h"
 
+#include "gstlibcamerapad.h"
+
 struct _GstLibcameraSrc {
 	GstElement parent;
 };
 
 G_DEFINE_TYPE(GstLibcameraSrc, gst_libcamera_src, GST_TYPE_ELEMENT);
 
+#define TEMPLATE_CAPS GST_STATIC_CAPS("video/x-raw; image/jpeg")
+
+/* For the simple case, we have a src pad that is always present. */
+GstStaticPadTemplate src_template = {
+	"src", GST_PAD_SRC, GST_PAD_ALWAYS, TEMPLATE_CAPS
+};
+
+/* More pads can be requested in state < PAUSED */
+GstStaticPadTemplate request_src_template = {
+	"src_%s", GST_PAD_SRC, GST_PAD_REQUEST, TEMPLATE_CAPS
+};
+
 static void
 gst_libcamera_src_init(GstLibcameraSrc *self)
 {
@@ -28,4 +42,10 @@ gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
 				       "libcamera Source", "Source/Video",
 				       "Linux Camera source using libcamera",
 				       "Nicolas Dufresne <nicolas.dufresne@collabora.com");
+	gst_element_class_add_static_pad_template_with_gtype(element_class,
+							     &src_template,
+							     GST_TYPE_LIBCAMERA_PAD);
+	gst_element_class_add_static_pad_template_with_gtype(element_class,
+							     &request_src_template,
+							     GST_TYPE_LIBCAMERA_PAD);
 }

src/gstreamer/meson.build

@@ -1,6 +1,7 @@
 libcamera_gst_sources = [
     'gstlibcamera-utils.cpp',
     'gstlibcamera.c',
+    'gstlibcamerapad.cpp',
     'gstlibcameraprovider.cpp',
     'gstlibcamerasrc.cpp',
 ]