1 files changed, 126 insertions, 0 deletions
diff --git a/include/linux/dma-buf-io.h b/include/linux/dma-buf-io.h
new file mode 100644
index 000000000000..d9f27650a851
--- /dev/null
+++ b/include/linux/dma-buf-io.h
@@ -0,0 +1,126 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __DMA_BUF_IO_H__
+#define __DMA_BUF_IO_H__
+
+#include <linux/dma-buf.h>
+
+struct dma_buf_io_ctx;
+struct dma_buf_io_map;
+
+struct dma_buf_io_ops {
+	/*
+	 * Create a new map for the given ctx. Called with the reservation
+	 * lock held.
+	 */
+	struct dma_buf_io_map *(*map)(struct dma_buf_io_ctx *ctx);
+
+	/*
+	 * Clean up device specific parts of the @map. Called with the
+	 * reservation lock held.
+	 */
+	void (*unmap)(struct dma_buf_io_ctx *ctx, struct dma_buf_io_map *map);
+
+	/*
+	 * The user tries to destroy the ctx. Release all device specific
+	 * parts of the token.
+	 */
+	void (*release)(struct dma_buf_io_ctx *);
+};
+
+struct dma_buf_io_map {
+	/*
+	 * Counts attached requests and other users. Device specific unmapping
+	 * is deferred until all refs are dropped.
+	 */
+	struct percpu_ref		refs;
+	/*
+	 * Shift for the minimum segment size of the mapping.
+	 */
+	unsigned			min_seg_shift;
+
+	struct dma_buf_io_ctx		*ctx;
+	struct completion		drained;
+};
+
+struct dma_buf_io_ctx {
+	struct dma_buf_io_map __rcu		*map;
+	struct dma_buf				*dmabuf;
+	enum dma_data_direction			dir;
+	bool					is_dead;
+
+	void					*dev_priv;
+	const struct dma_buf_io_ops		*dev_ops;
+};
+
+int dma_buf_io_ctx_create(struct file *file,
+			   struct dma_buf *dmabuf,
+			   enum dma_data_direction dir,
+			   struct dma_buf_io_ctx **ctx);
+void dma_buf_io_ctx_release(struct dma_buf_io_ctx *ctx);
+
+struct dma_buf_io_map *dma_buf_io_create_map(struct dma_buf_io_ctx *ctx);
+
+/* Internal helper, see dma_buf_io_get_map() */
+static inline struct dma_buf_io_map *
+__dma_buf_io_get_map(struct dma_buf_io_ctx *ctx)
+{
+	struct dma_buf_io_map *map;
+
+	guard(rcu)();
+
+	map = rcu_dereference(ctx->map);
+	if (unlikely(!map || !percpu_ref_tryget_live_rcu(&map->refs)))
+		return NULL;
+
+	return map;
+}
+
+/**
+ * dma_buf_io_get_map - Create a new or reference an existing map.
+ * @ctx:	[in]	dma-buf I/O context
+ * @nowait:	[in]	specifies whether it's allowed to block
+ *
+ * Create a new or acquire an existing map. On success, it returns
+ * a referenced map, which should eventually be put down with
+ * dma_buf_io_map_drop(). If @nowait is set and the function would block,
+ * it returns -EAGAIN, and the caller is expected to retry from a context
+ * where blocking is allowed.
+ *
+ * Returns a map on success, or ERR_PTR encoded errno otherwise.
+ */
+static inline struct dma_buf_io_map *
+dma_buf_io_get_map(struct dma_buf_io_ctx *ctx, bool nowait)
+{
+	struct dma_buf_io_map *map;
+
+	map = __dma_buf_io_get_map(ctx);
+	if (likely(map))
+		return map;
+
+	if (nowait)
+		return ERR_PTR(-EAGAIN);
+	return dma_buf_io_create_map(ctx);
+}
+
+/**
+ * dma_buf_io_map_drop - Drop the map.
+ * @map:	[in]	dma-buf I/O map
+ *
+ * Put down a reference to the @map acquired via dma_buf_io_get_map().
+ * Should be called as soon as I/O is completed.
+ */
+static inline void dma_buf_io_map_drop(struct dma_buf_io_map *map)
+{
+	percpu_ref_put(&map->refs);
+}
+
+/*
+ * Device API
+ */
+
+void dma_buf_io_invalidate_mappings(struct dma_buf_io_ctx *ctx);
+int dma_buf_io_init_map(struct dma_buf_io_ctx *ctx, struct dma_buf_io_map *map,
+			struct sg_table *sgt);
+void dma_buf_io_detach(struct dma_buf_io_ctx *ctx);
+
+#endif