[PATCH v5 07/10] media: videobuf2: Allow exporting of a struct dmabuf

[Jai Luthra <jai.luthra@ideasonboard.com>]

From: Dave Stevenson <dave.stevenson@raspberrypi.com>

videobuf2 only allowed exporting a dmabuf as a file descriptor,
but there are instances where having the struct dma_buf is
useful within the kernel.

Split the current implementation into two, one step which
exports a struct dma_buf, and the second which converts that
into an fd.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Tested-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
---
Changes in v5:
- Update documentation of return type to only ERR_PTR and not NULL
Changes in v4:
- Return a pointer to struct dmabuf instead of passing it as a double
  pointer argument and returning an int for errors (Laurent)
- Document the return type (Paul)
---
 drivers/media/common/videobuf2/videobuf2-core.c | 45 ++++++++++++++++---------
 include/media/videobuf2-core.h                  | 16 +++++++++
 2 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 5e318165659f..7b99d39d7cb1 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -2419,50 +2419,63 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long offset,
 	return 0;
 }
 
-int vb2_core_expbuf(struct vb2_queue *q, int *fd, struct vb2_buffer *vb,
-		    unsigned int plane, unsigned int flags)
+struct dma_buf *vb2_core_expbuf_dmabuf(struct vb2_queue *q,
+				       struct vb2_buffer *vb,
+				       unsigned int plane, unsigned int flags)
 {
 	struct vb2_plane *vb_plane;
-	int ret;
-	struct dma_buf *dbuf;
+	struct dma_buf *dmabuf;
 
 	if (q->memory != VB2_MEMORY_MMAP) {
 		dprintk(q, 1, "queue is not currently set up for mmap\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (!q->mem_ops->get_dmabuf) {
 		dprintk(q, 1, "queue does not support DMA buffer exporting\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (flags & ~(O_CLOEXEC | O_ACCMODE)) {
-		dprintk(q, 1, "queue does support only O_CLOEXEC and access mode flags\n");
-		return -EINVAL;
+		dprintk(q, 1, "queue supports only O_CLOEXEC and access mode flags\n");
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (plane >= vb->num_planes) {
 		dprintk(q, 1, "buffer plane out of range\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (vb2_fileio_is_active(q)) {
 		dprintk(q, 1, "expbuf: file io in progress\n");
-		return -EBUSY;
+		return ERR_PTR(-EBUSY);
 	}
 
 	vb_plane = &vb->planes[plane];
 
-	dbuf = call_ptr_memop(get_dmabuf,
-			      vb,
-			      vb_plane->mem_priv,
-			      flags & O_ACCMODE);
-	if (IS_ERR_OR_NULL(dbuf)) {
+	dmabuf = call_ptr_memop(get_dmabuf, vb, vb_plane->mem_priv,
+				flags & O_ACCMODE);
+	if (IS_ERR_OR_NULL(dmabuf)) {
 		dprintk(q, 1, "failed to export buffer %d, plane %d\n",
 			vb->index, plane);
-		return -EINVAL;
+		if (!dmabuf)
+			dmabuf = ERR_PTR(-EINVAL);
 	}
 
+	return dmabuf;
+}
+EXPORT_SYMBOL_GPL(vb2_core_expbuf_dmabuf);
+
+int vb2_core_expbuf(struct vb2_queue *q, int *fd, struct vb2_buffer *vb,
+		    unsigned int plane, unsigned int flags)
+{
+	struct dma_buf *dbuf;
+	int ret;
+
+	dbuf = vb2_core_expbuf_dmabuf(q, vb, plane, flags);
+	if (IS_ERR(dbuf))
+		return PTR_ERR(dbuf);
+
 	ret = dma_buf_fd(dbuf, flags & ~O_ACCMODE);
 	if (ret < 0) {
 		dprintk(q, 3, "buffer %d, plane %d failed to export (%d)\n",
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index feda638d0064..45bfe8a2a12a 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -954,6 +954,22 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type);
  */
 int vb2_core_streamoff(struct vb2_queue *q, unsigned int type);
 
+/**
+ * vb2_core_expbuf_dmabuf() - Export a buffer as a dma_buf structure
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue
+ * @vb:		pointer to &struct vb2_buffer
+ * @plane:	index of the plane to be exported, 0 for single plane queues
+ * @flags:	file flags for newly created file, as defined at
+ *		include/uapi/asm-generic/fcntl.h.
+ *		Currently, the only used flag is %O_CLOEXEC.
+ *		is supported, refer to manual of open syscall for more details.
+ *
+ * Return: returns a pointer to &struct dma_buf on success; an ERR_PTR otherwise.
+ */
+struct dma_buf *vb2_core_expbuf_dmabuf(struct vb2_queue *q,
+				       struct vb2_buffer *vb,
+				       unsigned int plane, unsigned int flags);
+
 /**
  * vb2_core_expbuf() - Export a buffer as a file descriptor.
  * @q:		pointer to &struct vb2_queue with videobuf2 queue.

-- 
2.55.0