gst: Add initial device provider

This feature is used with GstDeviceMonitor in order to enumerate
and monitor devices to be used with the source element. The resulting
GstDevice implementation is also used by application to abstract the
configuration of the source element.

Implementation notes:
  - libcamera does not support polling yet
  - The device ID isn't unique in libcamera yet
  - The "name" property does not yet exist in libcamerasrc yet

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>

4 files changed, 270 insertions, 2 deletions

diff --git a/src/gstreamer/gstlibcamera.c b/src/gstreamer/gstlibcamera.c
index 7dd94ca0..81c7bb19 100644
--- a/src/gstreamer/gstlibcamera.c
+++ b/src/gstreamer/gstlibcamera.c
@@ -6,13 +6,19 @@
  * gstlibcamera.c - GStreamer plugin
  */
 
+#include "gstlibcameraprovider.h"
 #include "gstlibcamerasrc.h"
 
 static gboolean
 plugin_init(GstPlugin *plugin)
 {
-	return gst_element_register(plugin, "libcamerasrc", GST_RANK_PRIMARY,
-				    GST_TYPE_LIBCAMERA_SRC);
+	if (!gst_element_register(plugin, "libcamerasrc", GST_RANK_PRIMARY,
+				  GST_TYPE_LIBCAMERA_SRC) ||
+	    !gst_device_provider_register(plugin, "libcameraprovider",
+					  GST_RANK_PRIMARY,
+					  GST_TYPE_LIBCAMERA_PROVIDER))
+		return FALSE;
+
 	return TRUE;
 }
 
diff --git a/src/gstreamer/gstlibcameraprovider.cpp b/src/gstreamer/gstlibcameraprovider.cpp
new file mode 100644
index 00000000..914ed4fb
--- /dev/null
+++ b/src/gstreamer/gstlibcameraprovider.cpp
@@ -0,0 +1,238 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * gstlibcameraprovider.c - GStreamer Device Provider
+ */
+
+#include "gstlibcameraprovider.h"
+
+#include <libcamera/camera.h>
+#include <libcamera/camera_manager.h>
+
+#include "gstlibcamerasrc.h"
+#include "gstlibcamera-utils.h"
+
+using namespace libcamera;
+
+GST_DEBUG_CATEGORY_STATIC(provider_debug);
+#define GST_CAT_DEFAULT provider_debug
+
+/**
+ * \struct _GstLibcameraDevice
+ * \brief libcamera GstDevice implementation
+ *
+ * This object is used by GstLibcameraProvider to abstract a libcamera
+ * device. It also provides helpers to create and configure the
+ * libcamerasrc GstElement to be used with this device. The implementation is
+ * private to the plugin.
+ */
+
+enum {
+	PROP_DEVICE_NAME = 1,
+};
+
+#define GST_TYPE_LIBCAMERA_DEVICE gst_libcamera_device_get_type()
+G_DECLARE_FINAL_TYPE(GstLibcameraDevice, gst_libcamera_device,
+		     GST_LIBCAMERA, DEVICE, GstDevice);
+
+struct _GstLibcameraDevice {
+	GstDevice parent;
+	gchar *name;
+};
+
+G_DEFINE_TYPE(GstLibcameraDevice, gst_libcamera_device, GST_TYPE_DEVICE);
+
+static GstElement *
+gst_libcamera_device_create_element(GstDevice *device, const gchar *name)
+{
+	GstElement *source = gst_element_factory_make("libcamerasrc", name);
+
+	/*
+	 * Provider and source lives in the same plugin, so making the source
+	 * should never fail.
+	 */
+	g_assert(source);
+
+	g_object_set(source, "camera-name", GST_LIBCAMERA_DEVICE(device)->name, nullptr);
+
+	return source;
+}
+
+static gboolean
+gst_libcamera_device_reconfigure_element(GstDevice *device,
+					 GstElement *element)
+{
+	if (!GST_LIBCAMERA_IS_SRC(element))
+		return FALSE;
+
+	g_object_set(element, "camera-name", GST_LIBCAMERA_DEVICE(device)->name, nullptr);
+
+	return TRUE;
+}
+
+static void
+gst_libcamera_device_set_property(GObject *object, guint prop_id,
+				  const GValue *value, GParamSpec *pspec)
+{
+	GstLibcameraDevice *device = GST_LIBCAMERA_DEVICE(object);
+
+	switch (prop_id) {
+	case PROP_DEVICE_NAME:
+		device->name = g_value_dup_string(value);
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
+		break;
+	}
+}
+
+static void
+gst_libcamera_device_init(GstLibcameraDevice *self)
+{
+}
+
+static void
+gst_libcamera_device_finalize(GObject *object)
+{
+	GstLibcameraDevice *self = GST_LIBCAMERA_DEVICE(object);
+	gpointer klass = gst_libcamera_device_parent_class;
+
+	g_free(self->name);
+
+	G_OBJECT_GET_CLASS(klass)->finalize(object);
+}
+
+static void
+gst_libcamera_device_class_init(GstLibcameraDeviceClass *klass)
+{
+	GstDeviceClass *device_class = GST_DEVICE_CLASS(klass);
+	GObjectClass *object_class = G_OBJECT_CLASS(klass);
+
+	device_class->create_element = gst_libcamera_device_create_element;
+	device_class->reconfigure_element = gst_libcamera_device_reconfigure_element;
+
+	object_class->set_property = gst_libcamera_device_set_property;
+	object_class->finalize = gst_libcamera_device_finalize;
+
+	GParamSpec *pspec = g_param_spec_string("name", "Name",
+						"The name of the camera device", "",
+						(GParamFlags)(G_PARAM_STATIC_STRINGS | G_PARAM_WRITABLE |
+							      G_PARAM_CONSTRUCT_ONLY));
+	g_object_class_install_property(object_class, PROP_DEVICE_NAME, pspec);
+}
+
+static GstDevice *
+gst_libcamera_device_new(const std::shared_ptr<Camera> &camera)
+{
+	g_autoptr(GstCaps) caps = gst_caps_new_empty();
+	const gchar *name = camera->name().c_str();
+	StreamRoles roles;
+
+	roles.push_back(StreamRole::VideoRecording);
+	std::unique_ptr<CameraConfiguration> config = camera->generateConfiguration(roles);
+
+	for (const StreamConfiguration &stream_cfg : *config) {
+		GstCaps *sub_caps = gst_libcamera_stream_formats_to_caps(stream_cfg.formats());
+		if (sub_caps)
+			gst_caps_append(caps, sub_caps);
+	}
+
+	return GST_DEVICE(g_object_new(GST_TYPE_LIBCAMERA_DEVICE,
+				       /* \todo Use a unique identifier instead of camera name. */
+				       "name", name,
+				       "display-name", name,
+				       "caps", caps,
+				       "device-class", "Source/Video",
+				       nullptr));
+}
+
+/**
+ * \struct _GstLibcameraProvider
+ * \brief libcamera GstDeviceProvider implementation
+ *
+ * This GstFeature is used by GstDeviceMonitor to probe the available
+ * libcamera devices. The implementation is private to the plugin.
+ */
+
+struct _GstLibcameraProvider {
+	GstDeviceProvider parent;
+	CameraManager *cm;
+};
+
+G_DEFINE_TYPE_WITH_CODE(GstLibcameraProvider, gst_libcamera_provider,
+			GST_TYPE_DEVICE_PROVIDER,
+			GST_DEBUG_CATEGORY_INIT(provider_debug, "libcamera-provider", 0,
+						"libcamera Device Provider"));
+
+static GList *
+gst_libcamera_provider_probe(GstDeviceProvider *provider)
+{
+	GstLibcameraProvider *self = GST_LIBCAMERA_PROVIDER(provider);
+	CameraManager *cm = self->cm;
+	GList *devices = nullptr;
+	gint ret;
+
+	GST_INFO_OBJECT(self, "Probing cameras using libcamera");
+
+	/* \todo Move the CameraMananger start()/stop() calls into
+	 * GstDeviceProvider start()/stop() virtual function when CameraMananger
+	 * gains monitoring support. Meanwhile we need to cycle start()/stop()
+	 * to ensure every probe() calls return the latest list.
+	 */
+	ret = cm->start();
+	if (ret) {
+		GST_ERROR_OBJECT(self, "Failed to retrieve device list: %s",
+				 g_strerror(-ret));
+		return nullptr;
+	}
+
+	for (const std::shared_ptr<Camera> &camera : cm->cameras()) {
+		GST_INFO_OBJECT(self, "Found camera '%s'", camera->name().c_str());
+		devices = g_list_append(devices,
+					g_object_ref_sink(gst_libcamera_device_new(camera)));
+	}
+
+	cm->stop();
+
+	return devices;
+}
+
+static void
+gst_libcamera_provider_init(GstLibcameraProvider *self)
+{
+	GstDeviceProvider *provider = GST_DEVICE_PROVIDER(self);
+
+	self->cm = new CameraManager();
+
+	/* Avoid devices being duplicated. */
+	gst_device_provider_hide_provider(provider, "v4l2deviceprovider");
+}
+
+static void
+gst_libcamera_provider_finalize(GObject *object)
+{
+	GstLibcameraProvider *self = GST_LIBCAMERA_PROVIDER(object);
+	gpointer klass = gst_libcamera_provider_parent_class;
+
+	delete self->cm;
+
+	return G_OBJECT_GET_CLASS(klass)->finalize(object);
+}
+
+static void
+gst_libcamera_provider_class_init(GstLibcameraProviderClass *klass)
+{
+	GstDeviceProviderClass *provider_class = GST_DEVICE_PROVIDER_CLASS(klass);
+	GObjectClass *object_class = G_OBJECT_CLASS(klass);
+
+	provider_class->probe = gst_libcamera_provider_probe;
+	object_class->finalize = gst_libcamera_provider_finalize;
+
+	gst_device_provider_class_set_metadata(provider_class,
+					       "libcamera Device Provider",
+					       "Source/Video",
+					       "List camera device using libcamera",
+					       "Nicolas Dufresne <nicolas.dufresne@collabora.com>");
+}
diff --git a/src/gstreamer/gstlibcameraprovider.h b/src/gstreamer/gstlibcameraprovider.h
new file mode 100644
index 00000000..bdd19db8
--- /dev/null
+++ b/src/gstreamer/gstlibcameraprovider.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * gstlibcameraprovider.h - GStreamer Device Provider
+ */
+
+#ifndef __GST_LIBCAMERA_PROVIDER_H__
+#define __GST_LIBCAMERA_PROVIDER_H__
+
+#include <gst/gst.h>
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_LIBCAMERA_PROVIDER gst_libcamera_provider_get_type()
+G_DECLARE_FINAL_TYPE(GstLibcameraProvider, gst_libcamera_provider,
+		     GST_LIBCAMERA, PROVIDER, GstDeviceProvider)
+
+G_END_DECLS
+
+#endif /* __GST_LIBCAMERA_PROVIDER_H__ */
+
diff --git a/src/gstreamer/meson.build b/src/gstreamer/meson.build
index 9b11a46f..7e26e3e1 100644
--- a/src/gstreamer/meson.build
+++ b/src/gstreamer/meson.build
@@ -1,6 +1,7 @@
 libcamera_gst_sources = [
     'gstlibcamera-utils.cpp',
     'gstlibcamera.c',
+    'gstlibcameraprovider.cpp',
     'gstlibcamerasrc.cpp',
 ]