auxiliary: support for transfers using staging resources

Direct3D 10/11 has no concept of transfers. Applications instead
create resources with a STAGING or DYNAMIC usage, copy between them
and the real resource and use Map to map the STAGING/DYNAMIC resource.

This util module allows to implement Gallium drivers as a Direct3D
driver would be implemented: transfers allocate a resource with
PIPE_USAGE_STAGING, and copy the data between it and the real resource
with resource_copy_region.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/util/u_staging.h b/src/gallium/auxiliary/util/u_staging.h
new file mode 100644
index 0000000000..f5976dadb1
--- /dev/null
+++ b/src/gallium/auxiliary/util/u_staging.h
@@ -0,0 +1,29 @@
+/* Implement transfers using staging resources like in DirectX 10/11 */
+
+#ifndef U_STAGING_H
+#define U_STAGING_H
+
+#include "pipe/p_state.h"
+
+struct util_staging_transfer {
+   struct pipe_transfer base;
+
+   /* if direct, same as base.resource, otherwise the temporary staging resource */
+   struct pipe_resource *staging_resource;
+};
+
+/* user must be stride, slice_stride and offset */
+/* pt->usage == PIPE_USAGE_DYNAMIC should be a good value to pass for direct */
+/* staging resource is currently created with PIPE_USAGE_DYNAMIC */
+struct util_staging_transfer *
+util_staging_transfer_new(struct pipe_context *pipe,
+           struct pipe_resource *pt,
+           struct pipe_subresource sr,
+           unsigned usage,
+           const struct pipe_box *box,
+           bool direct);
+
+void
+util_staging_transfer_destroy(struct pipe_context *pipe, struct pipe_transfer *ptx);
+
+#endif