[RFC][PATCH 1/2] dma-buf: add importer private data to attachment

[Seung-Woo Kim <sw0312.kim@samsung.com>]

dma-buf attachment has only exporter private data, but importer private data
can be useful for importer especially to re-import the same dma-buf.
To use importer private data in attachment of the device, the function to
search attachment in the attachment list of dma-buf is also added.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
---
 drivers/base/dma-buf.c  |   31 +++++++++++++++++++++++++++++++
 include/linux/dma-buf.h |    4 ++++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 08fe897..a1eaaf2 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -259,6 +259,37 @@ err_attach:
 EXPORT_SYMBOL_GPL(dma_buf_attach);
 
 /**
+ * dma_buf_get_attachment - Get attachment with the device from dma_buf's
+ * attachments list
+ * @dmabuf:	[in]	buffer to find device from.
+ * @dev:	[in]	device to be found.
+ *
+ * Returns struct dma_buf_attachment * attaching the device; may return
+ * negative error codes.
+ *
+ */
+struct dma_buf_attachment *dma_buf_get_attachment(struct dma_buf *dmabuf,
+						  struct device *dev)
+{
+	struct dma_buf_attachment *attach;
+
+	if (WARN_ON(!dmabuf || !dev))
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&dmabuf->lock);
+	list_for_each_entry(attach, &dmabuf->attachments, node) {
+		if (attach->dev == dev) {
+			mutex_unlock(&dmabuf->lock);
+			return attach;
+		}
+	}
+	mutex_unlock(&dmabuf->lock);
+
+	return ERR_PTR(-ENODEV);
+}
+EXPORT_SYMBOL_GPL(dma_buf_get_attachment);
+
+/**
  * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
  * optionally calls detach() of dma_buf_ops for device-specific detach
  * @dmabuf:	[in]	buffer to detach from.
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index dfac5ed..09cff0f 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -136,6 +136,7 @@ struct dma_buf {
  * @dev: device attached to the buffer.
  * @node: list of dma_buf_attachment.
  * @priv: exporter specific attachment data.
+ * @importer_priv: importer specific attachment data.
  *
  * This structure holds the attachment information between the dma_buf buffer
  * and its user device(s). The list contains one attachment struct per device
@@ -146,6 +147,7 @@ struct dma_buf_attachment {
 	struct device *dev;
 	struct list_head node;
 	void *priv;
+	void *importer_priv;
 };
 
 /**
@@ -164,6 +166,8 @@ static inline void get_dma_buf(struct dma_buf *dmabuf)
 
 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 							struct device *dev);
+struct dma_buf_attachment *dma_buf_get_attachment(struct dma_buf *dmabuf,
+							struct device *dev);
 void dma_buf_detach(struct dma_buf *dmabuf,
 				struct dma_buf_attachment *dmabuf_attach);
 
-- 
1.7.4.1