Motivated by a discussion with Christian and Thomas: Try to untangle a
bit what's relevant for importers and what's relevant for exporters.
Also add an assert that really only dynamic importers use the api
function, anything else doesn't make sense.
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: "Christian König" <christian.koenig@xxxxxxx>
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx
---
drivers/dma-buf/dma-buf.c | 19 ++++++++++++++++---
include/linux/dma-buf.h | 8 +++++---
2 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 00d5afe904cc..1065545e9ca1 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -809,9 +809,15 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
/**
* dma_buf_pin - Lock down the DMA-buf
- *
* @attach: [in] attachment which should be pinned
*
+ * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
+ * call this, and only for limited use cases like scanout and not for temporary
+ * pin operations. It is not permitted to allow userspace to pin arbitrary
+ * amounts of buffers through this interface.
+ *
+ * Buffers must be unpinned by calling dma_buf_unpin().
+ *
* Returns:
* 0 on success, negative error code on failure.
*/
@@ -820,6 +826,8 @@ int dma_buf_pin(struct dma_buf_attachment *attach)
struct dma_buf *dmabuf = attach->dmabuf;
int ret = 0;
+ WARN_ON(!dma_buf_attachment_is_dynamic(attach));
+
dma_resv_assert_held(dmabuf->resv);
if (dmabuf->ops->pin)
@@ -830,14 +838,19 @@ int dma_buf_pin(struct dma_buf_attachment *attach)
EXPORT_SYMBOL_GPL(dma_buf_pin);
/**
- * dma_buf_unpin - Remove lock from DMA-buf
- *
+ * dma_buf_unpin - Unpin a DMA-buf
* @attach: [in] attachment which should be unpinned
+ *
+ * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
+ * any mapping of @attach again and inform the importer through
+ * &dma_buf_attach_ops.move_notify.
*/
void dma_buf_unpin(struct dma_buf_attachment *attach)
{
struct dma_buf *dmabuf = attach->dmabuf;
+ WARN_ON(!dma_buf_attachment_is_dynamic(attach));
+
dma_resv_assert_held(dmabuf->resv);
if (dmabuf->ops->unpin)
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 43802a31b25d..628681bf6c99 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -86,13 +86,15 @@ struct dma_buf_ops {
* @pin:
*
* This is called by dma_buf_pin() and lets the exporter know that the
- * DMA-buf can't be moved any more.
+ * DMA-buf can't be moved any more. The exporter should pin the buffer
+ * into system memory to make sure it is generally accessible by other
+ * devices.
*
* This is called with the &dmabuf.resv object locked and is mutual
* exclusive with @cache_sgt_mapping.
*
- * This callback is optional and should only be used in limited use
- * cases like scanout and not for temporary pin operations.
+ * This is called automatically for non-dynamic importers from
+ * dma_buf_attach().
*
* Returns:
*
--
2.29.2
