diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/dma-resv.h | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h index 7bb7e7edbb6f..a749f229ae91 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -55,12 +55,30 @@ struct dma_resv_list; * This enum describes the different use cases for a dma_resv object and * controls which fences are returned when queried. * - * An important fact is that there is the order WRITE<READ and when the - * dma_resv object is asked for fences for one use case the fences for the - * lower use case are returned as well. + * An important fact is that there is the order KERNEL<WRITE<READ and + * when the dma_resv object is asked for fences for one use case the fences + * for the lower use case are returned as well. + * + * For example when asking for WRITE fences then the KERNEL fences are returned + * as well. Similar when asked for READ fences then both WRITE and KERNEL + * fences are returned as well. */ enum dma_resv_usage { /** + * @DMA_RESV_USAGE_KERNEL: For in kernel memory management only. + * + * This should only be used for things like copying or clearing memory + * with a DMA hardware engine for the purpose of kernel memory + * management. + * + * Drivers *always* must wait for those fences before accessing the + * resource protected by the dma_resv object. The only exception for + * that is when the resource is known to be locked down in place by + * pinning it previously. + */ + DMA_RESV_USAGE_KERNEL, + + /** * @DMA_RESV_USAGE_WRITE: Implicit write synchronization. * * This should only be used for userspace command submissions which add |