Re: [PATCH 1/2] dma-buf: replace dma_buf_export() with dma_buf_export_named()

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Mar 25, 2013 at 04:50:45PM +0530, Sumit Semwal wrote:
> 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!]
> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  Documentation/dma-buf-sharing.txt |   13 +++++++++++--
>  drivers/base/dma-buf.c            |   11 +++++++----
>  include/linux/dma-buf.h           |   11 +++++++++--
>  3 files changed, 27 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt
> index 4966b1b..0b23261 100644
> --- a/Documentation/dma-buf-sharing.txt
> +++ b/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
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index 2a7cb0d..d89102a 100644
> --- a/drivers/base/dma-buf.c
> +++ b/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);
>  
>  
>  /**
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 9978b61..6f55c04 100644
> --- a/include/linux/dma-buf.h
> +++ b/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);
> -- 
> 1.7.10.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch