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.

src/gallium/auxiliary/Makefile

@@ -131,6 +131,7 @@ C_SOURCES = \
 	util/u_sampler.c \
 	util/u_simple_shaders.c \
 	util/u_snprintf.c \
+	util/u_staging.c \
 	util/u_surface.c \
 	util/u_surfaces.c \
 	util/u_texture.c \

src/gallium/auxiliary/util/u_staging.c

@@ -0,0 +1,93 @@
+#include "util/u_staging.h"
+#include "pipe/p_context.h"
+#include "util/u_memory.h"
+#include "util/u_inlines.h"
+
+static void
+util_staging_resource_template(struct pipe_resource *pt, unsigned width, unsigned height, unsigned depth, struct pipe_resource *template)
+{
+   memset(template, 0, sizeof(struct pipe_resource));
+   if(pt->target != PIPE_BUFFER && depth <= 1)
+      template->target = PIPE_TEXTURE_2D;
+   else
+      template->target = pt->target;
+   template->format = pt->format;
+   template->width0 = width;
+   template->height0 = height;
+   template->depth0 = depth;
+   template->last_level = 0;
+   template->nr_samples = pt->nr_samples;
+   template->bind = 0;
+   template->usage = PIPE_USAGE_STAGING;
+   template->flags = 0;
+}
+
+inline 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)
+{
+   struct pipe_screen *pscreen = pipe->screen;
+   struct util_staging_transfer *tx;
+   struct pipe_resource staging_resource_template;
+
+   tx = CALLOC_STRUCT(util_staging_transfer);
+   if (!tx)
+      return NULL;
+
+   pipe_resource_reference(&tx->base.resource, pt);
+   tx->base.sr = sr;
+   tx->base.usage = usage;
+   tx->base.box = *box;
+
+   if (direct)
+   {
+      tx->staging_resource = pt;
+      return tx;
+   }
+
+   util_staging_resource_template(pt, box->width, box->height, box->depth, &staging_resource_template);
+   tx->staging_resource = pscreen->resource_create(pscreen, &staging_resource_template);
+   if (!tx->staging_resource)
+   {
+      pipe_resource_reference(&tx->base.resource, NULL);
+      FREE(tx);
+      return NULL;
+   }
+
+   if (usage & PIPE_TRANSFER_READ)
+   {
+      struct pipe_subresource dstsr;
+      dstsr.face = 0;
+      dstsr.level = 0;
+      for(unsigned zi = 0; zi < box->depth; ++zi)
+         pipe->resource_copy_region(pipe, tx->staging_resource, dstsr, 0, 0, 0, tx->base.resource, sr, box->x, box->y, box->z + zi, box->width, box->height);
+   }
+
+   return tx;
+}
+
+void
+util_staging_transfer_destroy(struct pipe_context *pipe, struct pipe_transfer *ptx)
+{
+   struct util_staging_transfer *tx = (struct util_staging_transfer *)ptx;
+
+   if (tx->staging_resource != tx->base.resource)
+   {
+      if(tx->base.usage & PIPE_TRANSFER_WRITE) {
+         struct pipe_subresource srcsr;
+         srcsr.face = 0;
+         srcsr.level = 0;
+         for(unsigned zi = 0; zi < tx->base.box.depth; ++zi)
+            pipe->resource_copy_region(pipe, tx->base.resource, tx->base.sr, tx->base.box.x, tx->base.box.y, tx->base.box.z + zi, tx->staging_resource, srcsr, 0, 0, 0, tx->base.box.width, tx->base.box.height);
+      }
+
+      pipe_resource_reference(&tx->staging_resource, NULL);
+   }
+
+   pipe_resource_reference(&ptx->resource, NULL);
+   FREE(ptx);
+}

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