Document how to obtain the size of a DMA-BUF. This is what
Wayland compositors are doing.
Mention the kernel version numbers from which DMA-BUF features are
available.
Signed-off-by: Simon Ser <contact@xxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
---
include/uapi/linux/dma-buf.h | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h
index 8e4a2ca0bcbf..c95f6d3457d2 100644
--- a/include/uapi/linux/dma-buf.h
+++ b/include/uapi/linux/dma-buf.h
@@ -47,9 +47,13 @@
*
* If the driver or API with which the client is interacting uses implicit
* synchronization, waiting for prior work to complete can be done via
- * poll() on the DMA buffer file descriptor. If the driver or API requires
- * explicit synchronization, the client may have to wait on a sync_file or
- * other synchronization primitive outside the scope of the DMA buffer API.
+ * poll() on the DMA buffer file descriptor from kernel version 3.17. If the
+ * driver or API requires explicit synchronization, the client may have to wait
+ * on a sync_file or other synchronization primitive outside the scope of the
+ * DMA buffer API.
+ *
+ * From kernel version 3.12, user-space can use llseek(2) with the ``SEEK_END``
+ * whence to obtain the size of a DMA-BUF.
*/
struct dma_buf_sync {
/**
--
2.36.1
