diff options
Diffstat (limited to 'include/linux/dma-resv.h')
| -rw-r--r-- | include/linux/dma-resv.h | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h index c8ccbc94d5d2..0637659a702c 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -62,6 +62,11 @@ struct dma_resv_list; * 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. + * + * Already used fences can be promoted in the sense that a fence with + * DMA_RESV_USAGE_BOOKKEEP could become DMA_RESV_USAGE_READ by adding it again + * with this usage. But fences can never be degraded in the sense that a fence + * with DMA_RESV_USAGE_WRITE could become DMA_RESV_USAGE_READ. */ enum dma_resv_usage { /** @@ -98,10 +103,15 @@ enum dma_resv_usage { * @DMA_RESV_USAGE_BOOKKEEP: No implicit sync. * * This should be used by submissions which don't want to participate in - * implicit synchronization. + * any implicit synchronization. + * + * The most common case are preemption fences, page table updates, TLB + * flushes as well as explicit synced user submissions. * - * The most common case are preemption fences as well as page table - * updates and their TLB flushes. + * Explicit synced user user submissions can be promoted to + * DMA_RESV_USAGE_READ or DMA_RESV_USAGE_WRITE as needed using + * dma_buf_import_sync_file() when implicit synchronization should + * become necessary after initial adding of the fence. */ DMA_RESV_USAGE_BOOKKEEP }; |