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Subject[PATCH 05/12] dma-buf: add explicit buffer pinning
Date
Add optional explicit pinning callbacks instead of implicitly assume the
exporter pins the buffer when a mapping is created.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
drivers/dma-buf/dma-buf.c | 39 +++++++++++++++++++++++++++++++++++++++
include/linux/dma-buf.h | 37 +++++++++++++++++++++++++++++++------
2 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index a3738fab3927..f23ff8355505 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -630,6 +630,41 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
}
EXPORT_SYMBOL_GPL(dma_buf_detach);

+/**
+ * dma_buf_pin - Lock down the DMA-buf
+ *
+ * @dmabuf: [in] DMA-buf to lock down.
+ *
+ * Returns:
+ * 0 on success, negative error code on failure.
+ */
+int dma_buf_pin(struct dma_buf *dmabuf)
+{
+ int ret = 0;
+
+ reservation_object_assert_held(dmabuf->resv);
+
+ if (dmabuf->ops->pin)
+ ret = dmabuf->ops->pin(dmabuf);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_pin);
+
+/**
+ * dma_buf_unpin - Remove lock from DMA-buf
+ *
+ * @dmabuf: [in] DMA-buf to unlock.
+ */
+void dma_buf_unpin(struct dma_buf *dmabuf)
+{
+ reservation_object_assert_held(dmabuf->resv);
+
+ if (dmabuf->ops->unpin)
+ dmabuf->ops->unpin(dmabuf);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unpin);
+
/**
* dma_buf_map_attachment_locked - Maps the buffer into _device_ address space
* with the reservation lock held. Is a wrapper for map_dma_buf() of the
@@ -666,6 +701,8 @@ dma_buf_map_attachment_locked(struct dma_buf_attachment *attach,
*/
if (attach->invalidate)
list_del(&attach->node);
+ else
+ dma_buf_pin(attach->dmabuf);
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
if (attach->invalidate)
list_add(&attach->node, &attach->dmabuf->attachments);
@@ -735,6 +772,8 @@ void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *attach,

attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
direction);
+ if (!attach->invalidate)
+ dma_buf_unpin(attach->dmabuf);
}
EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment_locked);

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index ece4638359a8..a615b74e5894 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -100,14 +100,40 @@ struct dma_buf_ops {
*/
void (*detach)(struct dma_buf *, struct dma_buf_attachment *);

+ /**
+ * @pin_dma_buf:
+ *
+ * This is called by dma_buf_pin and lets the exporter know that an
+ * importer assumes that the DMA-buf can't be invalidated any more.
+ *
+ * This is called with the dmabuf->resv object locked.
+ *
+ * This callback is optional.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure.
+ */
+ int (*pin)(struct dma_buf *);
+
+ /**
+ * @unpin_dma_buf:
+ *
+ * This is called by dma_buf_unpin and lets the exporter know that an
+ * importer doesn't need to the DMA-buf to stay were it is any more.
+ *
+ * This is called with the dmabuf->resv object locked.
+ *
+ * This callback is optional.
+ */
+ void (*unpin)(struct dma_buf *);
+
/**
* @map_dma_buf:
*
* This is called by dma_buf_map_attachment() and is used to map a
* shared &dma_buf into device address space, and it is mandatory. It
- * can only be called if @attach has been called successfully. This
- * essentially pins the DMA buffer into place, and it cannot be moved
- * any more
+ * can only be called if @attach has been called successfully.
*
* This call may sleep, e.g. when the backing storage first needs to be
* allocated, or moved to a location suitable for all currently attached
@@ -148,9 +174,6 @@ struct dma_buf_ops {
*
* This is called by dma_buf_unmap_attachment() and should unmap and
* release the &sg_table allocated in @map_dma_buf, and it is mandatory.
- * It should also unpin the backing storage if this is the last mapping
- * of the DMA buffer, it the exporter supports backing storage
- * migration.
*
* This is always called with the dmabuf->resv object locked when
* no_sgt_cache is true.
@@ -442,6 +465,8 @@ 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);

+int dma_buf_pin(struct dma_buf *dmabuf);
+void dma_buf_unpin(struct dma_buf *dmabuf);
struct sg_table *dma_buf_map_attachment_locked(struct dma_buf_attachment *,
enum dma_data_direction);
struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
--
2.17.1
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