va: context: instanciate VA display through GstContext

Add all the machinery to instanciate VA display through GstContext,
thus all va elements can share the same display and the user can set
a custom one.

sys/va/gstvah264dec.c

@@ -33,6 +33,7 @@
 #include "gstvadisplay_drm.h"
 #include "gstvapool.h"
 #include "gstvaprofile.h"
+#include "gstvautils.h"
 #include "gstvavideoformat.h"
 
 GST_DEBUG_CATEGORY_STATIC (gst_va_h264dec_debug);
@@ -56,6 +57,7 @@ struct _GstVaH264Dec
 {
   GstH264Decoder parent;
 
+  GstVaDisplay *display;
   GstVaDecoder *decoder;
 
   GstBufferPool *other_pool;
@@ -747,19 +749,15 @@ gst_va_h264_dec_new_sequence (GstH264Decoder * decoder, const GstH264SPS * sps,
 static gboolean
 gst_va_h264_dec_open (GstVideoDecoder * decoder)
 {
-  GstVaDisplay *display;
   GstVaH264Dec *self = GST_VA_H264_DEC (decoder);
   GstVaH264DecClass *klass = GST_VA_H264_DEC_GET_CLASS (decoder);
 
-  /* @XXX(victor): query pipeline's context */
-  display = gst_va_display_drm_new_from_path (klass->render_device_path);
-  if (!display)
+  if (!gst_va_ensure_element_data (decoder, klass->render_device_path,
+          &self->display))
     return FALSE;
 
   if (!self->decoder)
-    self->decoder = gst_va_decoder_new (display, H264);
-
-  gst_object_unref (display);
+    self->decoder = gst_va_decoder_new (self->display, H264);
 
   return (self->decoder != NULL);
 }
@@ -770,6 +768,7 @@ gst_va_h264_dec_close (GstVideoDecoder * decoder)
   GstVaH264Dec *self = GST_VA_H264_DEC (decoder);
 
   gst_clear_object (&self->decoder);
+  gst_clear_object (&self->display);
 
   return TRUE;
 }
@@ -837,6 +836,10 @@ gst_va_h264_dec_src_query (GstVideoDecoder * decoder, GstQuery * query)
   gboolean ret = FALSE;
 
   switch (GST_QUERY_TYPE (query)) {
+    case GST_QUERY_CONTEXT:{
+      return gst_va_handle_context_query (GST_ELEMENT_CAST (self), query,
+          self->display);
+    }
     case GST_QUERY_CAPS:{
       GstCaps *caps = NULL, *tmp, *filter = NULL;
 
@@ -867,6 +870,19 @@ gst_va_h264_dec_src_query (GstVideoDecoder * decoder, GstQuery * query)
   return ret;
 }
 
+static gboolean
+gst_va_h264_dec_sink_query (GstVideoDecoder * decoder, GstQuery * query)
+{
+  GstVaH264Dec *self = GST_VA_H264_DEC (decoder);
+
+  if (GST_QUERY_TYPE (query) == GST_QUERY_CONTEXT) {
+    return gst_va_handle_context_query (GST_ELEMENT_CAST (self), query,
+        self->display);
+  }
+
+  return GST_VIDEO_DECODER_CLASS (parent_class)->sink_query (decoder, query);
+}
+
 static gboolean
 gst_va_h264_dec_stop (GstVideoDecoder * decoder)
 {
@@ -1276,6 +1292,29 @@ wrong_caps:
   }
 }
 
+static void
+gst_va_h264_dec_set_context (GstElement * element, GstContext * context)
+{
+  GstVaDisplay *old_display, *new_display;
+  GstVaH264Dec *self = GST_VA_H264_DEC (element);
+  GstVaH264DecClass *klass = GST_VA_H264_DEC_GET_CLASS (self);
+
+  old_display = self->display ? gst_object_ref (self->display) : NULL;
+  gst_va_handle_set_context (element, context, klass->render_device_path,
+      &self->display);
+  new_display = self->display ? gst_object_ref (self->display) : NULL;
+
+  if (old_display && new_display && old_display != new_display && self->decoder) {
+    GST_ELEMENT_WARNING (element, RESOURCE, BUSY,
+        ("Can't replace VA display while operating"), (NULL));
+  }
+
+  gst_clear_object (&old_display);
+  gst_clear_object (&new_display);
+
+  GST_ELEMENT_CLASS (parent_class)->set_context (element, context);
+}
+
 static void
 gst_va_h264_dec_dispose (GObject * object)
 {
@@ -1328,11 +1367,14 @@ gst_va_h264_dec_class_init (gpointer g_class, gpointer class_data)
 
   gobject_class->dispose = gst_va_h264_dec_dispose;
 
+  element_class->set_context = gst_va_h264_dec_set_context;
+
   decoder_class->open = GST_DEBUG_FUNCPTR (gst_va_h264_dec_open);
   decoder_class->close = GST_DEBUG_FUNCPTR (gst_va_h264_dec_close);
   decoder_class->stop = GST_DEBUG_FUNCPTR (gst_va_h264_dec_stop);
   decoder_class->getcaps = GST_DEBUG_FUNCPTR (gst_va_h264_dec_sink_getcaps);
   decoder_class->src_query = GST_DEBUG_FUNCPTR (gst_va_h264_dec_src_query);
+  decoder_class->sink_query = GST_DEBUG_FUNCPTR (gst_va_h264_dec_sink_query);
   decoder_class->negotiate = GST_DEBUG_FUNCPTR (gst_va_h264_dec_negotiate);
   decoder_class->decide_allocation =
       GST_DEBUG_FUNCPTR (gst_va_h264_dec_decide_allocation);

sys/va/gstvautils.c

@@ -0,0 +1,344 @@
+/* GStreamer
+ * Copyright (C) 2020 Igalia, S.L.
+ *     Author: Víctor Jáquez <vjaquez@igalia.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 "gstvadisplay_drm.h"
+#include "gstvadisplay_wrapped.h"
+#include "gstvautils.h"
+
+GST_DEBUG_CATEGORY_STATIC (GST_CAT_CONTEXT);
+
+static void
+_init_context_debug (void)
+{
+#ifndef GST_DISABLE_GST_DEBUG
+  static volatile gsize _init = 0;
+
+  if (g_once_init_enter (&_init)) {
+    GST_DEBUG_CATEGORY_GET (GST_CAT_CONTEXT, "GST_CONTEXT");
+    g_once_init_leave (&_init, 1);
+  }
+#endif
+}
+
+static gboolean
+gst_va_display_found (GstElement * element, GstVaDisplay * display)
+{
+  _init_context_debug ();
+
+  if (display) {
+    GST_CAT_LOG_OBJECT (GST_CAT_CONTEXT, element, "already have a display (%p)",
+        display);
+    return TRUE;
+  }
+
+  return FALSE;
+}
+
+static gboolean
+pad_query (const GValue * item, GValue * value, gpointer user_data)
+{
+  GstPad *pad = g_value_get_object (item);
+  GstQuery *query = user_data;
+  gboolean res;
+
+  _init_context_debug ();
+
+  res = gst_pad_peer_query (pad, query);
+
+  if (res) {
+    g_value_set_boolean (value, TRUE);
+    return FALSE;
+  }
+
+  GST_CAT_INFO_OBJECT (GST_CAT_CONTEXT, pad, "pad peer query failed");
+  return TRUE;
+}
+
+static gboolean
+_gst_va_run_query (GstElement * element, GstQuery * query,
+    GstPadDirection direction)
+{
+  GstIterator *it;
+  GstIteratorFoldFunction func = pad_query;
+  GValue res = G_VALUE_INIT;
+
+  g_value_init (&res, G_TYPE_BOOLEAN);
+  g_value_set_boolean (&res, FALSE);
+
+  if (direction == GST_PAD_SRC)
+    it = gst_element_iterate_src_pads (element);
+  else
+    it = gst_element_iterate_sink_pads (element);
+
+  while (gst_iterator_fold (it, func, &res, query) == GST_ITERATOR_RESYNC)
+    gst_iterator_resync (it);
+
+  gst_iterator_free (it);
+
+  return g_value_get_boolean (&res);
+}
+
+static void
+_gst_context_query (GstElement * element, const gchar * context_type)
+{
+  GstQuery *query;
+  GstContext *ctxt = NULL;
+
+  _init_context_debug ();
+
+  /*  2a) Query downstream with GST_QUERY_CONTEXT for the context and
+   *      check if downstream already has a context of the specific type
+   *  2b) Query upstream as above.
+   */
+  query = gst_query_new_context (context_type);
+  if (_gst_va_run_query (element, query, GST_PAD_SRC)) {
+    gst_query_parse_context (query, &ctxt);
+    GST_CAT_INFO_OBJECT (GST_CAT_CONTEXT, element,
+        "found context (%p) in downstream query", ctxt);
+    gst_element_set_context (element, ctxt);
+  } else if (_gst_va_run_query (element, query, GST_PAD_SINK)) {
+    gst_query_parse_context (query, &ctxt);
+    GST_CAT_INFO_OBJECT (GST_CAT_CONTEXT, element,
+        "found context (%p) in upstream query", ctxt);
+    gst_element_set_context (element, ctxt);
+  } else {
+    /* 3) Post a GST_MESSAGE_NEED_CONTEXT message on the bus with
+     *    the required context type and afterwards check if a
+     *    usable context was set now as in 1). The message could
+     *    be handled by the parent bins of the element and the
+     *    application.
+     */
+    GstMessage *msg;
+
+    GST_CAT_INFO_OBJECT (GST_CAT_CONTEXT, element,
+        "posting need context message");
+    msg = gst_message_new_need_context (GST_OBJECT_CAST (element),
+        context_type);
+    gst_element_post_message (element, msg);
+  }
+
+  /*
+   * Whomever responds to the need-context message performs a
+   * GstElement::set_context() with the required context in which the element
+   * is required to update the display_ptr or call gst_va_handle_set_context().
+   */
+
+  gst_query_unref (query);
+}
+
+/*  4) Create a context by itself and post a GST_MESSAGE_HAVE_CONTEXT
+ *     message.
+ */
+void
+gst_va_element_propagate_display_context (GstElement * element,
+    GstVaDisplay * display)
+{
+  GstContext *ctxt;
+  GstMessage *msg;
+
+  if (!display) {
+    GST_ERROR_OBJECT (element, "Could not get GL display connection");
+    return;
+  }
+
+  _init_context_debug ();
+
+  ctxt = gst_context_new ("gst.va.display.handle", TRUE);
+  gst_context_set_va_display (ctxt, display);
+
+  GST_CAT_INFO_OBJECT (GST_CAT_CONTEXT, element,
+      "post have context (%p) message with display (%p)", ctxt, display);
+  msg = gst_message_new_have_context (GST_OBJECT_CAST (element), ctxt);
+  gst_element_post_message (element, msg);
+}
+
+gboolean
+gst_va_ensure_element_data (gpointer element, const gchar * render_device_path,
+    GstVaDisplay ** display_ptr)
+{
+  GstVaDisplay *display;
+
+  g_return_val_if_fail (element, FALSE);
+  g_return_val_if_fail (render_device_path, FALSE);
+  g_return_val_if_fail (display_ptr, FALSE);
+
+  /*  1) Check if the element already has a context of the specific
+   *     type.
+   */
+  if (gst_va_display_found (element, *display_ptr))
+    goto done;
+
+  _gst_context_query (element, "gst.va.display.handle");
+
+  /* Neighbour found and it updated the display */
+  if (gst_va_display_found (element, *display_ptr))
+    goto done;
+
+  /* If no neighbor, or application not interested, use drm */
+  display = gst_va_display_drm_new_from_path (render_device_path);
+
+  *display_ptr = display;
+
+  gst_va_element_propagate_display_context (element, display);
+
+done:
+  return *display_ptr != NULL;
+}
+
+gboolean
+gst_va_handle_set_context (GstElement * element, GstContext * context,
+    const gchar * render_device_path, GstVaDisplay ** display_ptr)
+{
+  GstVaDisplay *display_replacement = NULL;
+  const gchar *context_type, *type_name;
+
+  g_return_val_if_fail (display_ptr, FALSE);
+
+  if (!context)
+    return FALSE;
+
+  context_type = gst_context_get_context_type (context);
+
+  if (g_strcmp0 (context_type, "gst.va.display.handle") == 0) {
+    type_name = G_OBJECT_TYPE_NAME (element);
+    if (!gst_context_get_va_display (context, type_name, render_device_path,
+            &display_replacement)) {
+      GST_CAT_WARNING_OBJECT (GST_CAT_CONTEXT, element,
+          "Failed to get display from context");
+      return FALSE;
+    }
+  }
+
+  if (display_replacement) {
+    GstVaDisplay *old = *display_ptr;
+    *display_ptr = display_replacement;
+
+    if (old)
+      gst_object_unref (old);
+  }
+
+  return TRUE;
+}
+
+gboolean
+gst_va_handle_context_query (GstElement * element, GstQuery * query,
+    GstVaDisplay * display)
+{
+  const gchar *context_type;
+  GstContext *ctxt, *old_ctxt;
+
+  g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
+  g_return_val_if_fail (GST_IS_QUERY (query), FALSE);
+  g_return_val_if_fail (display && GST_IS_VA_DISPLAY (display), FALSE);
+
+  GST_CAT_LOG_OBJECT (GST_CAT_CONTEXT, element,
+      "handle context query %" GST_PTR_FORMAT, query);
+  gst_query_parse_context_type (query, &context_type);
+
+  if (!display || g_strcmp0 (context_type, "gst.va.display.handle") != 0)
+    return FALSE;
+
+  gst_query_parse_context (query, &old_ctxt);
+
+  if (old_ctxt)
+    ctxt = gst_context_copy (old_ctxt);
+  else
+    ctxt = gst_context_new ("gst.va.display.handle", TRUE);
+
+  gst_context_set_va_display (ctxt, display);
+  gst_query_set_context (query, ctxt);
+  gst_context_unref (ctxt);
+  GST_CAT_DEBUG_OBJECT (GST_CAT_CONTEXT, element,
+      "successuflly %" GST_PTR_FORMAT " on %" GST_PTR_FORMAT, display, query);
+
+  return TRUE;
+}
+
+gboolean
+gst_context_get_va_display (GstContext * context, const gchar * type_name,
+    const gchar * render_device_path, GstVaDisplay ** display_ptr)
+{
+  const GstStructure *s;
+  GstVaDisplay *display = NULL;
+  gpointer dpy;
+  gboolean is_devnode;
+
+  g_return_val_if_fail (display_ptr, FALSE);
+  g_return_val_if_fail (context, FALSE);
+
+  is_devnode = (g_strstr_len (type_name, -1, "renderD") != NULL);
+
+  s = gst_context_get_structure (context);
+  if (gst_structure_get (s, "gst-display", GST_TYPE_VA_DISPLAY, &display, NULL)) {
+    gchar *device_path = NULL;
+
+    if (GST_IS_VA_DISPLAY_DRM (display)) {
+      g_object_get (display, "path", &device_path, NULL);
+      if (g_strcmp0 (device_path, render_device_path) == 0)
+        goto accept;
+    } else if (!is_devnode) {
+      goto accept;
+    }
+
+    /* let's try other fields */
+    gst_clear_object (&display);
+  }
+
+  /* if element is render device node specific, it doesn't accept
+   * VADisplay from users */
+  if (!is_devnode
+      && gst_structure_get (s, "va-display", G_TYPE_POINTER, &dpy, NULL)) {
+    if ((display = gst_va_display_wrapped_new ((guintptr) dpy)))
+      goto accept;
+  }
+
+  GST_CAT_DEBUG (GST_CAT_CONTEXT, "No valid GstVaDisplay from context (%p)",
+      context);
+  return FALSE;
+
+accept:
+  {
+    *display_ptr = display;
+
+    GST_CAT_LOG (GST_CAT_CONTEXT, "got GstVaDisplay (%p) from context (%p)",
+        *display_ptr, context);
+    return TRUE;
+  }
+}
+
+void
+gst_context_set_va_display (GstContext * context, GstVaDisplay * display)
+{
+  GstStructure *s;
+
+  g_return_if_fail (context != NULL);
+
+  if (display)
+    GST_CAT_LOG (GST_CAT_CONTEXT,
+        "setting GstVaDisplay (%" GST_PTR_FORMAT ") on context (%"
+        GST_PTR_FORMAT ")", display, context);
+
+  s = gst_context_writable_structure (context);
+  gst_structure_set (s, "gst-display", GST_TYPE_VA_DISPLAY, display, NULL);
+}

sys/va/gstvautils.h

@@ -0,0 +1,48 @@
+/* GStreamer
+ * Copyright (C) 2020 Igalia, S.L.
+ *     Author: Víctor Jáquez <vjaquez@igalia.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.
+ */
+
+#pragma once
+
+#include "gstvadisplay.h"
+
+G_BEGIN_DECLS
+
+gboolean              gst_va_ensure_element_data          (gpointer element,
+							   const gchar *render_device_path,
+							   GstVaDisplay ** display_ptr);
+gboolean              gst_va_handle_set_context           (GstElement * element,
+							   GstContext * context,
+							   const gchar *render_device_path,
+							   GstVaDisplay ** display_ptr);
+gboolean              gst_va_handle_context_query         (GstElement * element,
+							   GstQuery * query,
+							   GstVaDisplay * display);
+void                  gst_va_element_propagate_display_context (GstElement * element,
+								GstVaDisplay * display);
+
+gboolean              gst_context_get_va_display          (GstContext * context,
+							   const gchar * type_name,
+							   const gchar * render_device_path,
+							   GstVaDisplay ** display_ptr);
+void                  gst_context_set_va_display          (GstContext * context,
+							   GstVaDisplay * display);
+
+
+G_END_DECLS

sys/va/meson.build

@@ -10,6 +10,7 @@ va_sources = [
   'gstvah264dec.c',
   'gstvapool.c',
   'gstvaprofile.c',
+  'gstvautils.c',
   'gstvavideoformat.c',
 ]