v4l2codec: Add GstV4L2Deocder helper object

This is a GstObject which will be used to hold on media and video device file
descriptor and provide abstracted ioctl calls with these descriptor. At the
moment this helper contains just enough to enumerate the supported format.
This part will be used by the plugin to register the CODEC specific elements..

sys/v4l2codecs/gstv4l2decoder.c

@@ -0,0 +1,214 @@
+/* GStreamer
+ * Copyright (C) 2020 Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "gstv4l2decoder.h"
+#include "linux/media.h"
+#include "linux/videodev2.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+GST_DEBUG_CATEGORY (v4l2_decoder_debug);
+#define GST_CAT_DEFAULT v4l2_decoder_debug
+
+enum
+{
+  PROP_0,
+  PROP_MEDIA_DEVICE,
+  PROP_VIDEO_DEVICE,
+};
+
+struct _GstV4l2Decoder
+{
+  GstObject parent;
+
+  gboolean opened;
+  gint media_fd;
+  gint video_fd;
+
+  /* properties */
+  gchar *media_device;
+  gchar *video_device;
+};
+
+G_DEFINE_TYPE_WITH_CODE (GstV4l2Decoder, gst_v4l2_decoder, GST_TYPE_OBJECT,
+    GST_DEBUG_CATEGORY_INIT (v4l2_decoder_debug, "v4l2codecs-decoder", 0,
+        "V4L2 stateless decoder helper"));
+
+static void
+gst_v4l2_decoder_finalize (GObject * obj)
+{
+  GstV4l2Decoder *self = GST_V4L2_DECODER (obj);
+
+  if (self->media_fd)
+    close (self->media_fd);
+  if (self->video_fd)
+    close (self->media_fd);
+
+  g_free (self->media_device);
+  g_free (self->video_device);
+
+  G_OBJECT_CLASS (gst_v4l2_decoder_parent_class)->finalize (obj);
+}
+
+static void
+gst_v4l2_decoder_init (GstV4l2Decoder * self)
+{
+}
+
+static void
+gst_v4l2_decoder_class_init (GstV4l2DecoderClass * klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->finalize = gst_v4l2_decoder_finalize;
+  gobject_class->get_property = gst_v4l2_decoder_get_property;
+  gobject_class->set_property = gst_v4l2_decoder_set_property;
+
+  gst_v4l2_decoder_install_properties (gobject_class, 0, NULL);
+}
+
+GstV4l2Decoder *
+gst_v4l2_decoder_new (GstV4l2CodecDevice * device)
+{
+  GstV4l2Decoder *decoder;
+
+  g_return_val_if_fail (device->function == MEDIA_ENT_F_PROC_VIDEO_DECODER,
+      NULL);
+
+  decoder = g_object_new (GST_TYPE_V4L2_DECODER,
+      "media-device", device->media_device_path,
+      "video-device", device->video_device_path, NULL);
+
+  return gst_object_ref_sink (decoder);
+}
+
+gboolean
+gst_v4l2_decoder_open (GstV4l2Decoder * self)
+{
+  self->media_fd = open (self->media_device, 0);
+  if (self->media_fd < 0) {
+    GST_ERROR_OBJECT (self, "Failed to open '%s': %s",
+        self->media_device, g_strerror (errno));
+    return FALSE;
+  }
+
+  self->video_fd = open (self->video_device, 0);
+  if (self->video_fd < 0) {
+    GST_ERROR_OBJECT (self, "Failed to open '%s': %s",
+        self->video_device, g_strerror (errno));
+    return FALSE;
+  }
+
+  self->opened = TRUE;
+
+  return TRUE;
+}
+
+gboolean
+gst_v4l2_decoder_enum_input_fmt (GstV4l2Decoder * self, gint i,
+    guint32 * out_fmt)
+{
+  struct v4l2_fmtdesc fmtdesc = { i, V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE, };
+  gint ret;
+
+  g_return_val_if_fail (self->opened, FALSE);
+
+  ret = ioctl (self->video_fd, VIDIOC_ENUM_FMT, &fmtdesc);
+  if (ret < 0) {
+    if (errno != EINVAL)
+      GST_ERROR_OBJECT (self, "VIDIOC_ENUM_FMT failed: %s", g_strerror (errno));
+    return FALSE;
+  }
+
+  GST_DEBUG_OBJECT (self, "Found format %" GST_FOURCC_FORMAT " (%s)",
+      GST_FOURCC_ARGS (fmtdesc.pixelformat), fmtdesc.description);
+  *out_fmt = fmtdesc.pixelformat;
+
+  return TRUE;
+}
+
+void
+gst_v4l2_decoder_install_properties (GObjectClass * gobject_class,
+    gint prop_offset, GstV4l2CodecDevice * device)
+{
+  const gchar *media_device_path = NULL;
+  const gchar *video_device_path = NULL;
+
+  if (device) {
+    media_device_path = device->media_device_path;
+    video_device_path = device->video_device_path;
+  }
+
+  g_object_class_install_property (gobject_class, PROP_MEDIA_DEVICE,
+      g_param_spec_string ("media-device", "Media Device Path",
+          "Path to the media device node", media_device_path,
+          G_PARAM_CONSTRUCT_ONLY | G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
+  g_object_class_install_property (gobject_class, PROP_VIDEO_DEVICE,
+      g_param_spec_string ("video-device", "Video Device Path",
+          "Path to the video device node", video_device_path,
+          G_PARAM_CONSTRUCT_ONLY | G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+}
+
+void
+gst_v4l2_decoder_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstV4l2Decoder *self = GST_V4L2_DECODER (object);
+
+  switch (prop_id) {
+    case PROP_MEDIA_DEVICE:
+      g_free (self->media_device);
+      self->media_device = g_value_dup_string (value);
+      break;
+    case PROP_VIDEO_DEVICE:
+      g_free (self->video_device);
+      self->video_device = g_value_dup_string (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+void
+gst_v4l2_decoder_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstV4l2Decoder *self = GST_V4L2_DECODER (object);
+
+  switch (prop_id) {
+    case PROP_MEDIA_DEVICE:
+      g_value_set_string (value, self->media_device);
+      break;
+    case PROP_VIDEO_DEVICE:
+      g_value_set_string (value, self->video_device);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}

sys/v4l2codecs/gstv4l2decoder.h

@@ -0,0 +1,52 @@
+/* GStreamer
+ * Copyright (C) 2020 Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __GST_V4L2_DECODER_H__
+#define __GST_V4L2_DECODER_H__
+
+#include <gst/gst.h>
+#include <gst/video/video.h>
+
+#include "gstv4l2codecdevice.h"
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_V4L2_DECODER gst_v4l2_decoder_get_type ()
+G_DECLARE_FINAL_TYPE (GstV4l2Decoder, gst_v4l2_decoder, GST, V4L2_DECODER, GstObject);
+
+GstV4l2Decoder *  gst_v4l2_decoder_new (GstV4l2CodecDevice * device);
+
+gboolean          gst_v4l2_decoder_open (GstV4l2Decoder * decoder);
+
+gboolean          gst_v4l2_decoder_enum_input_fmt (GstV4l2Decoder * self,
+                                                   gint i, guint32 * out_fmt);
+
+void              gst_v4l2_decoder_install_properties (GObjectClass * gobject_class,
+                                                       gint prop_offset,
+                                                       GstV4l2CodecDevice * device);
+
+void              gst_v4l2_decoder_set_property (GObject * object, guint prop_id,
+                                                 const GValue * value, GParamSpec * pspec);
+
+void              gst_v4l2_decoder_get_property (GObject * object, guint prop_id,
+                                                 GValue * value, GParamSpec * pspec);
+
+G_END_DECLS
+
+#endif /* __GST_V4L2_DECODER_H__ */

sys/v4l2codecs/meson.build

@@ -1,6 +1,7 @@
 v4l2codecs_sources = [
   'plugin.c',
   'gstv4l2codecdevice.c',
+  'gstv4l2decoder.c',
 ]
 
 libgudev_dep = dependency('gudev-1.0', required: get_option('v4l2codecs'))