[1/2] dmabuf: add DMA_BUF_IOCTL_RW_FILE

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 5baa83b85515..95d8b0158ffd 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -460,6 +460,7 @@  static long dma_buf_ioctl(struct file *file,
 	struct dma_buf *dmabuf;
 	struct dma_buf_sync sync;
 	enum dma_data_direction direction;
+	struct dma_buf_rw_file kfile;
 	int ret;
 
 	dmabuf = file->private_data;
@@ -504,6 +505,13 @@  static long dma_buf_ioctl(struct file *file,
 		return dma_buf_import_sync_file(dmabuf, (const void __user *)arg);
 #endif
 
+	case DMA_BUF_IOCTL_RW_FILE:
+		if (copy_from_user(&kfile, (void __user *) arg, sizeof(kfile)))
+			return -EFAULT;
+		if (!dmabuf->ops->rw_file)
+			return -EINVAL;
+		return dmabuf->ops->rw_file(dmabuf, &kfile);
+
 	default:
 		return -ENOTTY;
 	}
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 36216d28d8bd..de236ba2094b 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -22,6 +22,7 @@ 
 #include <linux/fs.h>
 #include <linux/dma-fence.h>
 #include <linux/wait.h>
+#include <uapi/linux/dma-buf.h>
 
 struct device;
 struct dma_buf;
@@ -285,6 +286,8 @@  struct dma_buf_ops {
 
 	int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
 	void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
+
+	int (*rw_file)(struct dma_buf *dmabuf, struct dma_buf_rw_file *file);
 };
 
 /**
diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h
index 5a6fda66d9ad..ec9164b7b753 100644
--- a/include/uapi/linux/dma-buf.h
+++ b/include/uapi/linux/dma-buf.h
@@ -167,6 +167,29 @@  struct dma_buf_import_sync_file {
 	__s32 fd;
 };
 
+/**
+ * struct dma_buf_rw_file - read/write file associated with a dma-buf
+ *
+ * Userspace can performs a DMA_BUF_IOCTL_BACK to save data from a dma-buf or
+ * restore data to a dma-buf.
+ */
+struct dma_buf_rw_file {
+
+	/** @flags: Flags indicating read/write for this dma-buf. */
+	__u32 flags;
+	/** @fd: File descriptor of the file associated with this dma-buf. */
+	__s32 fd;
+	/** @file_offset: Offset within the file where this dma-buf starts.
+	 *
+	 *  Offset and Length must be page-aligned for direct I/O.
+	 */
+	__u64 file_offset;
+	/** @buf_offset: Offset within this dma-buf where the read/write starts. */
+	__u64 buf_offset;
+	/** @buf_len: Length of this dma-buf read/write. */
+	__u64 buf_len;
+};
+
 #define DMA_BUF_BASE		'b'
 #define DMA_BUF_IOCTL_SYNC	_IOW(DMA_BUF_BASE, 0, struct dma_buf_sync)
 
@@ -179,4 +202,10 @@  struct dma_buf_import_sync_file {
 #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)
 
+#define DMA_BUF_RW_FLAGS_OP_MASK (0xFF << 0)
+#define DMA_BUF_RW_FLAGS_READ (1 << 0) /* Restore dma-buf data */
+#define DMA_BUF_RW_FLAGS_WRITE (2 << 0) /* Save dma-buf data */
+#define DMA_BUF_RW_FLAGS_DIRECT (1u << 31) /* Direct read/write file */
+#define DMA_BUF_IOCTL_RW_FILE	_IOW(DMA_BUF_BASE, 4, struct dma_buf_rw_file)
+
 #endif