The in-fence implementation involves having a per-buffer fence callback,
that triggers on the fence signal. The fence callback is called asynchronously
and needs a valid reference to the associated ideobuf2 buffer.

Allow this by making the vb2_buffer refcounted, so it can be passed
to other contexts.

Signed-off-by: Ezequiel Garcia <ezequ...@collabora.com>
---
 drivers/media/common/videobuf2/videobuf2-core.c | 27 ++++++++++++++++++++++---
 include/media/videobuf2-core.h                  |  7 +++++--
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c 
b/drivers/media/common/videobuf2/videobuf2-core.c
index d3f7bb33a54d..f1feb45c1e37 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -190,6 +190,26 @@ module_param(debug, int, 0644);
 static void __vb2_queue_cancel(struct vb2_queue *q);
 static void __enqueue_in_driver(struct vb2_buffer *vb);
 
+static void __vb2_buffer_free(struct kref *kref)
+{
+       struct vb2_buffer *vb =
+               container_of(kref, struct vb2_buffer, refcount);
+       kfree(vb);
+}
+
+static void __vb2_buffer_put(struct vb2_buffer *vb)
+{
+       if (vb)
+               kref_put(&vb->refcount, __vb2_buffer_free);
+}
+
+static struct vb2_buffer *__vb2_buffer_get(struct vb2_buffer *vb)
+{
+       if (vb)
+               kref_get(&vb->refcount);
+       return vb;
+}
+
 /*
  * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
  */
@@ -346,6 +366,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum 
vb2_memory memory,
                        break;
                }
 
+               kref_init(&vb->refcount);
                vb->state = VB2_BUF_STATE_DEQUEUED;
                vb->vb2_queue = q;
                vb->num_planes = num_planes;
@@ -365,7 +386,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum 
vb2_memory memory,
                                dprintk(1, "failed allocating memory for buffer 
%d\n",
                                        buffer);
                                q->bufs[vb->index] = NULL;
-                               kfree(vb);
+                               __vb2_buffer_put(vb);
                                break;
                        }
                        __setup_offsets(vb);
@@ -380,7 +401,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum 
vb2_memory memory,
                                        buffer, vb);
                                __vb2_buf_mem_free(vb);
                                q->bufs[vb->index] = NULL;
-                               kfree(vb);
+                               __vb2_buffer_put(vb);
                                break;
                        }
                }
@@ -520,7 +541,7 @@ static int __vb2_queue_free(struct vb2_queue *q, unsigned 
int buffers)
        /* Free videobuf buffers */
        for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
             ++buffer) {
-               kfree(q->bufs[buffer]);
+               __vb2_buffer_put(q->bufs[buffer]);
                q->bufs[buffer] = NULL;
        }
 
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index f6818f732f34..baa4632c7e59 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -12,11 +12,12 @@
 #ifndef _MEDIA_VIDEOBUF2_CORE_H
 #define _MEDIA_VIDEOBUF2_CORE_H
 
+#include <linux/bitops.h>
+#include <linux/dma-buf.h>
+#include <linux/kref.h>
 #include <linux/mm_types.h>
 #include <linux/mutex.h>
 #include <linux/poll.h>
-#include <linux/dma-buf.h>
-#include <linux/bitops.h>
 
 #define VB2_MAX_FRAME  (32)
 #define VB2_MAX_PLANES (8)
@@ -249,6 +250,7 @@ struct vb2_buffer {
 
        /* private: internal use only
         *
+        * refcount:            refcount for this buffer
         * state:               current buffer state; do not change
         * queued_entry:        entry on the queued buffers list, which holds
         *                      all buffers queued from userspace
@@ -256,6 +258,7 @@ struct vb2_buffer {
         *                      to be dequeued to userspace
         * vb2_plane:           per-plane information; do not change
         */
+       struct kref             refcount;
        enum vb2_buffer_state   state;
 
        struct vb2_plane        planes[VB2_MAX_PLANES];
-- 
2.16.3

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