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 <[email protected]> Cc: Daniel Vetter <[email protected]> Cc: Jason Ekstrand <[email protected]> --- 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
