nouveau: Add implementation of MapRenderbuffer.

Perhaps the easiest implementation, nouveau can directly map buffers
even if tiled, and uses separate surfaces for its texture
renderbuffers so we don't have to worry about that offset.

Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/drivers/dri/nouveau/nouveau_fbo.c

@@ -133,6 +133,50 @@ nouveau_renderbuffer_new(struct gl_context *ctx, GLuint name)
 	return rb;
 }
 
+static void
+nouveau_renderbuffer_map(struct gl_context *ctx,
+			 struct gl_renderbuffer *rb,
+			 GLuint x, GLuint y, GLuint w, GLuint h,
+			 GLbitfield mode,
+			 GLubyte **out_map,
+			 GLint *out_stride)
+{
+	struct nouveau_surface *s = &to_nouveau_renderbuffer(rb)->surface;
+	GLubyte *map;
+	int stride;
+	int flags = 0;
+
+	if (mode & GL_MAP_READ_BIT)
+		flags |= NOUVEAU_BO_RD;
+	if (mode & GL_MAP_WRITE_BIT)
+		flags |= NOUVEAU_BO_WR;
+
+	nouveau_bo_map(s->bo, flags);
+
+	map = s->bo->map;
+	stride = s->pitch;
+
+	if (rb->Name == 0) {
+		map += stride * (rb->Height - 1);
+		stride = -stride;
+	}
+
+	map += x * s->cpp;
+	map += (int)y * stride;
+
+	*out_map = map;
+	*out_stride = stride;
+}
+
+static void
+nouveau_renderbuffer_unmap(struct gl_context *ctx,
+			   struct gl_renderbuffer *rb)
+{
+	struct nouveau_surface *s = &to_nouveau_renderbuffer(rb)->surface;
+
+	nouveau_bo_unmap(s->bo);
+}
+
 static GLboolean
 nouveau_renderbuffer_dri_storage(struct gl_context *ctx, struct gl_renderbuffer *rb,
 				 GLenum internalFormat,
@@ -268,6 +312,8 @@ nouveau_fbo_functions_init(struct dd_function_table *functions)
 #if FEATURE_EXT_framebuffer_object
 	functions->NewFramebuffer = nouveau_framebuffer_new;
 	functions->NewRenderbuffer = nouveau_renderbuffer_new;
+	functions->MapRenderbuffer = nouveau_renderbuffer_map;
+	functions->UnmapRenderbuffer = nouveau_renderbuffer_unmap;
 	functions->BindFramebuffer = nouveau_bind_framebuffer;
 	functions->FramebufferRenderbuffer = nouveau_framebuffer_renderbuffer;
 	functions->RenderTexture = nouveau_render_texture;