dma-buf: replace dma_buf_export() with dma_buf_export_named()

For debugging purposes, it is useful to have a name-string added
while exporting buffers. Hence, dma_buf_export() is replaced with
dma_buf_export_named(), which additionally takes 'exp_name' as a
parameter.

For backward compatibility, and for lazy exporters who don't wish to
name themselves, a #define dma_buf_export() is also made available,
which adds a __FILE__ instead of 'exp_name'.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
  [Thanks for the idea!]
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

Documentation/dma-buf-sharing.txt

@@ -52,14 +52,23 @@ The dma_buf buffer sharing API usage contains the following steps:
    associated with this buffer.
 
    Interface:
-      struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,
-				     size_t size, int flags)
+      struct dma_buf *dma_buf_export_named(void *priv, struct dma_buf_ops *ops,
+				     size_t size, int flags,
+				     const char *exp_name)
 
    If this succeeds, dma_buf_export allocates a dma_buf structure, and returns a
    pointer to the same. It also associates an anonymous file with this buffer,
    so it can be exported. On failure to allocate the dma_buf object, it returns
    NULL.
 
+   'exp_name' is the name of exporter - to facilitate information while
+   debugging.
+
+   Exporting modules which do not wish to provide any specific name may use the
+   helper define 'dma_buf_export()', with the same arguments as above, but
+   without the last argument; a __FILE__ pre-processor directive will be
+   inserted in place of 'exp_name' instead.
+
 2. Userspace gets a handle to pass around to potential buffer-users
 
    Userspace entity requests for a file-descriptor (fd) which is a handle to the

drivers/base/dma-buf.c

@@ -77,22 +77,24 @@ static inline int is_dma_buf_file(struct file *file)
 }
 
 /**
- * dma_buf_export - Creates a new dma_buf, and associates an anon file
+ * dma_buf_export_named - Creates a new dma_buf, and associates an anon file
  * with this buffer, so it can be exported.
  * Also connect the allocator specific data and ops to the buffer.
+ * Additionally, provide a name string for exporter; useful in debugging.
  *
  * @priv:	[in]	Attach private data of allocator to this buffer
  * @ops:	[in]	Attach allocator-defined dma buf ops to the new buffer.
  * @size:	[in]	Size of the buffer
  * @flags:	[in]	mode flags for the file.
+ * @exp_name:	[in]	name of the exporting module - useful for debugging.
  *
  * Returns, on success, a newly created dma_buf object, which wraps the
  * supplied private data and operations for dma_buf_ops. On either missing
  * ops, or error in allocating struct dma_buf, will return negative error.
  *
  */
-struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
-				size_t size, int flags)
+struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
+				size_t size, int flags, const char *exp_name)
 {
 	struct dma_buf *dmabuf;
 	struct file *file;
@@ -114,6 +116,7 @@ struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
 	dmabuf->priv = priv;
 	dmabuf->ops = ops;
 	dmabuf->size = size;
+	dmabuf->exp_name = exp_name;
 
 	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
 
@@ -124,7 +127,7 @@ struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
 
 	return dmabuf;
 }
-EXPORT_SYMBOL_GPL(dma_buf_export);
+EXPORT_SYMBOL_GPL(dma_buf_export_named);
 
 
 /**

include/linux/dma-buf.h

@@ -112,6 +112,7 @@ struct dma_buf_ops {
  * @file: file pointer used for sharing buffers across, and for refcounting.
  * @attachments: list of dma_buf_attachment that denotes all devices attached.
  * @ops: dma_buf_ops associated with this buffer object.
+ * @exp_name: name of the exporter; useful for debugging.
  * @priv: exporter specific private data for this buffer object.
  */
 struct dma_buf {
@@ -123,6 +124,7 @@ struct dma_buf {
 	struct mutex lock;
 	unsigned vmapping_counter;
 	void *vmap_ptr;
+	const char *exp_name;
 	void *priv;
 };
 
@@ -162,8 +164,13 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 							struct device *dev);
 void dma_buf_detach(struct dma_buf *dmabuf,
 				struct dma_buf_attachment *dmabuf_attach);
-struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
-			       size_t size, int flags);
+
+struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
+			       size_t size, int flags, const char *);
+
+#define dma_buf_export(priv, ops, size, flags)	\
+	dma_buf_export_named(priv, ops, size, flags, __FILE__)
+
 int dma_buf_fd(struct dma_buf *dmabuf, int flags);
 struct dma_buf *dma_buf_get(int fd);
 void dma_buf_put(struct dma_buf *dmabuf);