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

Sumit Semwal
2013-03-25T11:21:22Z

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>
---
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