drm_driver: Add a configuration function to the driver descriptor.

Adds a possibility for the state tracker manager to query the
target for a specific configuration.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

src/gallium/include/state_tracker/drm_driver.h

@@ -35,6 +35,40 @@ struct winsys_handle
    unsigned stride;
 };
 
+
+
+/**
+ * Configuration queries.
+ */
+enum drm_conf {
+   /* How many frames to allow before throttling. Or -1 to indicate any number */
+   DRM_CONF_THROTTLE, /* DRM_CONF_INT. */
+   DRM_CONF_MAX
+};
+
+/**
+ * Type of configuration answer
+ */
+enum drm_conf_type {
+   DRM_CONF_INT,
+   DRM_CONF_BOOL,
+   DRM_CONF_FLOAT,
+   DRM_CONF_POINTER
+};
+
+/**
+ * Return value from the configuration function.
+ */
+struct drm_conf_ret {
+   enum drm_conf_type type;
+   union {
+      int val_int;
+      bool val_bool;
+      float val_float;
+      void *val_pointer;
+   } val;
+};
+
 struct drm_driver_descriptor
 {
    /**
@@ -54,6 +88,16 @@ struct drm_driver_descriptor
     * For example wrapping trace or rbug debugging drivers around it.
     */
    struct pipe_screen* (*create_screen)(int drm_fd);
+
+
+   /**
+    * Return a configuration value.
+    *
+    * If this function is NULL, or if it returns NULL
+    * the state tracker- or state
+    * tracker manager should provide a reasonable default value.
+    */
+   const struct drm_conf_ret *(*configuration) (enum drm_conf conf);
 };
 
 extern struct drm_driver_descriptor driver_descriptor;
@@ -61,11 +105,12 @@ extern struct drm_driver_descriptor driver_descriptor;
 /**
  * Instantiate a drm_driver_descriptor struct.
  */
-#define DRM_DRIVER_DESCRIPTOR(name_str, driver_name_str, func) \
+#define DRM_DRIVER_DESCRIPTOR(name_str, driver_name_str, func, conf) \
 struct drm_driver_descriptor driver_descriptor = {             \
    .name = name_str,                                           \
    .driver_name = driver_name_str,                             \
    .create_screen = func,                                      \
+   .configuration = (conf),				       \
 };
 
 #endif