diff options
| -rw-r--r-- | drivers/dma-buf/dma-buf.c | 3 | ||||
| -rw-r--r-- | include/linux/dma-buf.h | 15 |
2 files changed, 18 insertions, 0 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index d0121402c58c..510b42771974 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -951,6 +951,9 @@ EXPORT_SYMBOL_GPL(dma_buf_unpin); * the underlying backing storage is pinned for as long as a mapping exists, * therefore users/importers should not hold onto a mapping for undue amounts of * time. + * + * Important: Dynamic importers must wait for the exclusive fence of the struct + * dma_resv attached to the DMA-BUF first. */ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, enum dma_data_direction direction) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 342585bd6dff..92eec38a03aa 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -96,6 +96,12 @@ struct dma_buf_ops { * This is called automatically for non-dynamic importers from * dma_buf_attach(). * + * Note that similar to non-dynamic exporters in their @map_dma_buf + * callback the driver must guarantee that the memory is available for + * use and cleared of any old data by the time this function returns. + * Drivers which pipeline their buffer moves internally must wait for + * all moves and clears to complete. + * * Returns: * * 0 on success, negative error code on failure. @@ -144,6 +150,15 @@ struct dma_buf_ops { * This is always called with the dmabuf->resv object locked when * the dynamic_mapping flag is true. * + * Note that for non-dynamic exporters the driver must guarantee that + * that the memory is available for use and cleared of any old data by + * the time this function returns. Drivers which pipeline their buffer + * moves internally must wait for all moves and clears to complete. + * Dynamic exporters do not need to follow this rule: For non-dynamic + * importers the buffer is already pinned through @pin, which has the + * same requirements. Dynamic importers otoh are required to obey the + * dma_resv fences. + * * Returns: * * A &sg_table scatter list of or the backing storage of the DMA buffer, |