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-rw-r--r--include/linux/dma-buf.h84
1 files changed, 84 insertions, 0 deletions
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index b1523cb8..5a6fda66 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -85,6 +85,88 @@ struct dma_buf_sync {
#define DMA_BUF_NAME_LEN 32
+/**
+ * struct dma_buf_export_sync_file - Get a sync_file from a dma-buf
+ *
+ * Userspace can perform a DMA_BUF_IOCTL_EXPORT_SYNC_FILE to retrieve the
+ * current set of fences on a dma-buf file descriptor as a sync_file. CPU
+ * waits via poll() or other driver-specific mechanisms typically wait on
+ * whatever fences are on the dma-buf at the time the wait begins. This
+ * is similar except that it takes a snapshot of the current fences on the
+ * dma-buf for waiting later instead of waiting immediately. This is
+ * useful for modern graphics APIs such as Vulkan which assume an explicit
+ * synchronization model but still need to inter-operate with dma-buf.
+ *
+ * The intended usage pattern is the following:
+ *
+ * 1. Export a sync_file with flags corresponding to the expected GPU usage
+ * via DMA_BUF_IOCTL_EXPORT_SYNC_FILE.
+ *
+ * 2. Submit rendering work which uses the dma-buf. The work should wait on
+ * the exported sync file before rendering and produce another sync_file
+ * when complete.
+ *
+ * 3. Import the rendering-complete sync_file into the dma-buf with flags
+ * corresponding to the GPU usage via DMA_BUF_IOCTL_IMPORT_SYNC_FILE.
+ *
+ * Unlike doing implicit synchronization via a GPU kernel driver's exec ioctl,
+ * the above is not a single atomic operation. If userspace wants to ensure
+ * ordering via these fences, it is the respnosibility of userspace to use
+ * locks or other mechanisms to ensure that no other context adds fences or
+ * submits work between steps 1 and 3 above.
+ */
+struct dma_buf_export_sync_file {
+ /**
+ * @flags: Read/write flags
+ *
+ * Must be DMA_BUF_SYNC_READ, DMA_BUF_SYNC_WRITE, or both.
+ *
+ * If DMA_BUF_SYNC_READ is set and DMA_BUF_SYNC_WRITE is not set,
+ * the returned sync file waits on any writers of the dma-buf to
+ * complete. Waiting on the returned sync file is equivalent to
+ * poll() with POLLIN.
+ *
+ * If DMA_BUF_SYNC_WRITE is set, the returned sync file waits on
+ * any users of the dma-buf (read or write) to complete. Waiting
+ * on the returned sync file is equivalent to poll() with POLLOUT.
+ * If both DMA_BUF_SYNC_WRITE and DMA_BUF_SYNC_READ are set, this
+ * is equivalent to just DMA_BUF_SYNC_WRITE.
+ */
+ __u32 flags;
+ /** @fd: Returned sync file descriptor */
+ __s32 fd;
+};
+
+/**
+ * struct dma_buf_import_sync_file - Insert a sync_file into a dma-buf
+ *
+ * Userspace can perform a DMA_BUF_IOCTL_IMPORT_SYNC_FILE to insert a
+ * sync_file into a dma-buf for the purposes of implicit synchronization
+ * with other dma-buf consumers. This allows clients using explicitly
+ * synchronized APIs such as Vulkan to inter-op with dma-buf consumers
+ * which expect implicit synchronization such as OpenGL or most media
+ * drivers/video.
+ */
+struct dma_buf_import_sync_file {
+ /**
+ * @flags: Read/write flags
+ *
+ * Must be DMA_BUF_SYNC_READ, DMA_BUF_SYNC_WRITE, or both.
+ *
+ * If DMA_BUF_SYNC_READ is set and DMA_BUF_SYNC_WRITE is not set,
+ * this inserts the sync_file as a read-only fence. Any subsequent
+ * implicitly synchronized writes to this dma-buf will wait on this
+ * fence but reads will not.
+ *
+ * If DMA_BUF_SYNC_WRITE is set, this inserts the sync_file as a
+ * write fence. All subsequent implicitly synchronized access to
+ * this dma-buf will wait on this fence.
+ */
+ __u32 flags;
+ /** @fd: Sync file descriptor */
+ __s32 fd;
+};
+
#define DMA_BUF_BASE 'b'
#define DMA_BUF_IOCTL_SYNC _IOW(DMA_BUF_BASE, 0, struct dma_buf_sync)
@@ -94,5 +176,7 @@ struct dma_buf_sync {
#define DMA_BUF_SET_NAME _IOW(DMA_BUF_BASE, 1, const char *)
#define DMA_BUF_SET_NAME_A _IOW(DMA_BUF_BASE, 1, __u32)
#define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64)
+#define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, struct dma_buf_export_sync_file)
+#define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file)
#endif