gallium: Add drm driver interface

This interfacre replaces the drm_api api it works very much the same
way as drm_api but with the exception that its meant for the target
to implement it. And it does not export a get function and neither a
destroy function.

src/gallium/include/state_tracker/drm_driver.h

@@ -0,0 +1,71 @@
+
+#ifndef _DRM_DRIVER_H_
+#define _DRM_DRIVER_H_
+
+#include "pipe/p_compiler.h"
+
+struct pipe_screen;
+struct pipe_winsys;
+struct pipe_context;
+struct pipe_resource;
+
+#define DRM_API_HANDLE_TYPE_SHARED 0
+#define DRM_API_HANDLE_TYPE_KMS    1
+
+/**
+ * For use with pipe_screen::{texture_from_handle|texture_get_handle}.
+ */
+struct winsys_handle
+{
+   /**
+    * Unused for texture_from_handle, always
+    * DRM_API_HANDLE_TYPE_SHARED.  Input to texture_get_handle,
+    * use TEXTURE_USAGE to select handle for kms or ipc.
+    */
+   unsigned type;
+   /**
+    * Input to texture_from_handle.
+    * Output for texture_get_handle.
+    */
+   unsigned handle;
+   /**
+    * Input to texture_from_handle.
+    * Output for texture_get_handle.
+    */
+   unsigned stride;
+};
+
+struct drm_driver_descriptor
+{
+   /**
+    * Identifying sufix/prefix of the binary, used by egl.
+    */
+   const char *name;
+
+   /**
+    * Kernel driver name, as accepted by drmOpenByName.
+    */
+   const char *driver_name;
+
+   /**
+    * Create a pipe srcreen.
+    *
+    * This function does any wrapping of the screen.
+    * For example wrapping trace or rbug debugging drivers around it.
+    */
+   struct pipe_screen* (*create_screen)(int drm_fd);
+};
+
+extern struct drm_driver_descriptor driver_descriptor;
+
+/**
+ * Instantiate a drm_driver_descriptor struct.
+ */
+#define DRM_DRIVER_DESCRIPTOR(name_str, driver_name_str, func) \
+struct drm_driver_descriptor driver_descriptor = {             \
+   .name = name_str,                                           \
+   .driver_name = driver_name_str,                             \
+   .create_screen = func,                                      \
+};
+
+#endif