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Subject[PATCHv3 1/1] staging/ion: Add support to get ion handle from dma buf
Date
Currently we can only import dma buf fd's to get ion_handle.
Adding support to import dma buf handles to support kernel
specific use cases.

An example use case is in linux platforms such as Tizen, in which
DRM-GEM is used for buffer management for graphics. It has gem_handle
corresponding to a buffer and uses gem_name for sharing the buffer
with other processes. However,it also uses dma_buf fd for 3d operations.
For wayland, there are multiple calls for gem_handle to dma_buf fd
conversion. So, we store dma_buf associated with buffer. But, there is
no api for getting ion_handle from dma_buf. This patch exposes api to
retrieve the ion handle from dma_buf for similar use cases. With this
patch, we can integrate ION within DRM-GEM for buffer management and
dma_buf sharing.

Signed-off-by: Rohit kumar <rohit.kr@samsung.com>
---
v2: Updated commit message with use case explanation, as suggested by
Laura Abbott<labbott@redhat.com>
v3: Fixed dmabuf refcount issue in ion_import_dma_buf. dma_buf_put()
was being called without dma_buf_get(), so moving it to
ion_import_dma_buf_fd().

drivers/staging/android/ion/ion.c | 26 ++++++++++++++++++--------
drivers/staging/android/ion/ion.h | 20 ++++++++++++++++----
2 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index e237e9f..7e86e18 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -1151,22 +1151,18 @@ int ion_share_dma_buf_fd(struct ion_client *client, struct ion_handle *handle)
}
EXPORT_SYMBOL(ion_share_dma_buf_fd);

-struct ion_handle *ion_import_dma_buf(struct ion_client *client, int fd)
+struct ion_handle *ion_import_dma_buf(struct ion_client *client,
+ struct dma_buf *dmabuf)
{
- struct dma_buf *dmabuf;
struct ion_buffer *buffer;
struct ion_handle *handle;
int ret;

- dmabuf = dma_buf_get(fd);
- if (IS_ERR(dmabuf))
- return ERR_CAST(dmabuf);
/* if this memory came from ion */

if (dmabuf->ops != &dma_buf_ops) {
pr_err("%s: can not import dmabuf from another exporter\n",
__func__);
- dma_buf_put(dmabuf);
return ERR_PTR(-EINVAL);
}
buffer = dmabuf->priv;
@@ -1194,11 +1190,25 @@ struct ion_handle *ion_import_dma_buf(struct ion_client *client, int fd)
}

end:
- dma_buf_put(dmabuf);
return handle;
}
EXPORT_SYMBOL(ion_import_dma_buf);

+struct ion_handle *ion_import_dma_buf_fd(struct ion_client *client, int fd)
+{
+ struct dma_buf *dmabuf;
+ struct ion_handle *handle;
+
+ dmabuf = dma_buf_get(fd);
+ if (IS_ERR(dmabuf))
+ return ERR_CAST(dmabuf);
+
+ handle = ion_import_dma_buf(client, dmabuf);
+ dma_buf_put(dmabuf);
+ return handle;
+}
+EXPORT_SYMBOL(ion_import_dma_buf_fd);
+
static int ion_sync_for_device(struct ion_client *client, int fd)
{
struct dma_buf *dmabuf;
@@ -1306,7 +1316,7 @@ static long ion_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct ion_handle *handle;

- handle = ion_import_dma_buf(client, data.fd.fd);
+ handle = ion_import_dma_buf_fd(client, data.fd.fd);
if (IS_ERR(handle))
ret = PTR_ERR(handle);
else
diff --git a/drivers/staging/android/ion/ion.h b/drivers/staging/android/ion/ion.h
index b860c5f..a1331fc 100644
--- a/drivers/staging/android/ion/ion.h
+++ b/drivers/staging/android/ion/ion.h
@@ -192,14 +192,26 @@ struct dma_buf *ion_share_dma_buf(struct ion_client *client,
int ion_share_dma_buf_fd(struct ion_client *client, struct ion_handle *handle);

/**
- * ion_import_dma_buf() - given an dma-buf fd from the ion exporter get handle
+ * ion_import_dma_buf() - get ion_handle from dma-buf
+ * @client: the client
+ * @dmabuf: the dma-buf
+ *
+ * Get the ion_buffer associated with the dma-buf and return the ion_handle.
+ * If no ion_handle exists for this buffer, return newly created ion_handle.
+ * If dma-buf from another exporter is passed, return ERR_PTR(-EINVAL)
+ */
+struct ion_handle *ion_import_dma_buf(struct ion_client *client,
+ struct dma_buf *dmabuf);
+
+/**
+ * ion_import_dma_buf_fd() - given a dma-buf fd from the ion exporter get handle
* @client: the client
* @fd: the dma-buf fd
*
- * Given an dma-buf fd that was allocated through ion via ion_share_dma_buf,
- * import that fd and return a handle representing it. If a dma-buf from
+ * Given an dma-buf fd that was allocated through ion via ion_share_dma_buf_fd,
+ * import that fd and return a handle representing it. If a dma-buf from
* another exporter is passed in this function will return ERR_PTR(-EINVAL)
*/
-struct ion_handle *ion_import_dma_buf(struct ion_client *client, int fd);
+struct ion_handle *ion_import_dma_buf_fd(struct ion_client *client, int fd);

#endif /* _LINUX_ION_H */
--
1.7.9.5
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