kms: Export DMABuf from Dumb buffer when possible

https://bugzilla.gnome.org/show_bug.cgi?id=787593

sys/kms/gstkmsallocator.c

@@ -27,6 +27,7 @@
 #include "config.h"
 #endif
 
+#include <fcntl.h>
 #include <xf86drm.h>
 #include <xf86drmMode.h>
 #include <stdlib.h>
@@ -37,6 +38,8 @@
 /* it needs to be below because is internal to libdrm */
 #include <drm.h>
 
+#include <gst/allocators/gstdmabuf.h>
+
 #include "gstkmsallocator.h"
 #include "gstkmsutils.h"
 
@@ -58,6 +61,7 @@ struct _GstKMSAllocatorPrivate
   int fd;
   /* protected by GstKMSAllocator object lock */
   GList *mem_cache;
+  GstAllocator *dmabuf_alloc;
 };
 
 #define parent_class gst_kms_allocator_parent_class
@@ -297,6 +301,9 @@ gst_kms_allocator_finalize (GObject * obj)
 
   gst_kms_allocator_clear_cache (GST_ALLOCATOR (alloc));
 
+  if (alloc->priv->dmabuf_alloc)
+    gst_object_unref (alloc->priv->dmabuf_alloc);
+
   if (check_fd (alloc))
     close (alloc->priv->fd);
 
@@ -555,6 +562,48 @@ failed:
   }
 }
 
+GstMemory *
+gst_kms_allocator_dmabuf_export (GstAllocator * allocator, GstMemory * _kmsmem)
+{
+  GstKMSMemory *kmsmem = (GstKMSMemory *) _kmsmem;
+  GstKMSAllocator *alloc = GST_KMS_ALLOCATOR (allocator);
+  GstMemory *mem;
+  gint ret;
+  gint prime_fd;
+
+  /* We can only export DUMB buffers */
+  g_return_val_if_fail (kmsmem->bo, NULL);
+
+
+  ret = drmPrimeHandleToFD (alloc->priv->fd, kmsmem->bo->handle,
+      DRM_CLOEXEC | DRM_RDWR, &prime_fd);
+  if (ret)
+    goto export_fd_failed;
+
+  if (G_UNLIKELY (alloc->priv->dmabuf_alloc == NULL))
+    alloc->priv->dmabuf_alloc = gst_dmabuf_allocator_new ();
+
+  mem = gst_dmabuf_allocator_alloc (alloc->priv->dmabuf_alloc, prime_fd,
+      gst_memory_get_sizes (_kmsmem, NULL, NULL));
+
+  /* Populate the cache so KMSSink can find the kmsmem back when it receives
+   * one of these DMABuf. This call takes ownership of the kmsmem. */
+  gst_kms_allocator_cache (allocator, mem, _kmsmem);
+
+  GST_DEBUG_OBJECT (alloc, "Exported bo handle %d as %d", kmsmem->bo->handle,
+      prime_fd);
+
+  return mem;
+
+  /* ERRORS */
+export_fd_failed:
+  {
+    GST_ERROR_OBJECT (alloc, "Failed to export bo handle %d: %s (%d)",
+        kmsmem->bo->handle, g_strerror (errno), ret);
+    return NULL;
+  }
+}
+
 /* FIXME, using gdata for caching on upstream memory is not tee safe */
 GstMemory *
 gst_kms_allocator_get_cached (GstMemory * mem)

sys/kms/gstkmsallocator.h

@@ -86,6 +86,9 @@ GstKMSMemory* gst_kms_allocator_dmabuf_import (GstAllocator *allocator,
 					       gsize offsets[GST_VIDEO_MAX_PLANES],
 					       GstVideoInfo *vinfo);
 
+GstMemory*    gst_kms_allocator_dmabuf_export (GstAllocator *allocator,
+                                               GstMemory *kmsmem);
+
 GstMemory *   gst_kms_allocator_get_cached  (GstMemory * mem);
 
 void          gst_kms_allocator_clear_cache (GstAllocator * allocator);

sys/kms/gstkmsbufferpool.c

@@ -40,6 +40,7 @@ struct _GstKMSBufferPoolPrivate
   GstVideoInfo vinfo;
   GstAllocator *allocator;
   gboolean add_videometa;
+  gboolean has_prime_export;
 };
 
 #define parent_class gst_kms_buffer_pool_parent_class
@@ -52,7 +53,9 @@ static const gchar **
 gst_kms_buffer_pool_get_options (GstBufferPool * pool)
 {
   static const gchar *options[] = { GST_BUFFER_POOL_OPTION_VIDEO_META,
-    GST_BUFFER_POOL_OPTION_KMS_BUFFER, NULL
+    GST_BUFFER_POOL_OPTION_KMS_BUFFER,
+    GST_BUFFER_POOL_OPTION_KMS_PRIME_EXPORT,
+    NULL
   };
   return options;
 }
@@ -97,6 +100,8 @@ gst_kms_buffer_pool_set_config (GstBufferPool * pool, GstStructure * config)
   /* enable metadata based on config of the pool */
   priv->add_videometa = gst_buffer_pool_config_has_option (config,
       GST_BUFFER_POOL_OPTION_VIDEO_META);
+  priv->has_prime_export = gst_buffer_pool_config_has_option (config,
+      GST_BUFFER_POOL_OPTION_KMS_PRIME_EXPORT);
 
   return GST_BUFFER_POOL_CLASS (parent_class)->set_config (pool, config);
 
@@ -141,6 +146,16 @@ gst_kms_buffer_pool_alloc_buffer (GstBufferPool * pool, GstBuffer ** buffer,
   if (!mem)
     goto no_memory;
 
+  if (vpool->priv->has_prime_export) {
+    GstMemory *dmabufmem;
+
+    dmabufmem = gst_kms_allocator_dmabuf_export (priv->allocator, mem);
+    if (dmabufmem)
+      mem = dmabufmem;
+    else
+      GST_WARNING_OBJECT (pool, "Failed to export DMABuf from Dumb buffer.");
+  }
+
   *buffer = gst_buffer_new ();
   gst_buffer_append_memory (*buffer, mem);
 

sys/kms/gstkmsbufferpool.h

@@ -37,10 +37,19 @@ G_BEGIN_DECLS
  * GST_BUFFER_POOL_OPTION_KMS_BUFFER:
  *
  * An option that can be activated on buffer pool to request KMS
- * buffers.
+ * buffers. NOT IMPLEMENTED
  */
 #define GST_BUFFER_POOL_OPTION_KMS_BUFFER "GstBufferPoolOptionKMSBuffer"
 
+/**
+ * GST_BUFFER_POOL_OPTION_KMS_PRIME_EXPORT:
+ *
+ * An option that can be activated on buffer pool to request DMABuf
+ * buffers. Callers are responsible to check if this is supported. Dumb buffers
+ * will be returned if not supported.
+ */
+#define GST_BUFFER_POOL_OPTION_KMS_PRIME_EXPORT "GstBufferPoolOptionKMSPrimeExport"
+
 /* video bufferpool */
 typedef struct _GstKMSBufferPool GstKMSBufferPool;
 typedef struct _GstKMSBufferPoolClass GstKMSBufferPoolClass;

sys/kms/gstkmssink.c

@@ -932,6 +932,14 @@ gst_kms_sink_propose_allocation (GstBaseSink * bsink, GstQuery * query)
     pool = gst_kms_sink_create_pool (self, caps, size, 0);
     if (!pool)
       goto no_pool;
+
+    /* Only export for pool used upstream */
+    if (self->has_prime_export) {
+      GstStructure *config = gst_buffer_pool_get_config (pool);
+      gst_buffer_pool_config_add_option (config,
+          GST_BUFFER_POOL_OPTION_KMS_PRIME_EXPORT);
+      gst_buffer_pool_set_config (pool, config);
+    }
   }
 
   /* we need at least 2 buffer because we hold on to the last one */