drm/ttm: Make ttm_bo_mem_compat available

There are cases where it is desired to see if a proposed placement
is compatible with a buffer object before calling ttm_bo_validate().

Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Cc: <stable@vger.kernel.org>
---
This is the first of a 3-patch series to fix a black screen
issue observed on Ubuntu 16.04 server.

drivers/gpu/drm/ttm/ttm_bo.c

@@ -1034,9 +1034,9 @@ out_unlock:
 	return ret;
 }
 
-static bool ttm_bo_mem_compat(struct ttm_placement *placement,
-			      struct ttm_mem_reg *mem,
-			      uint32_t *new_flags)
+bool ttm_bo_mem_compat(struct ttm_placement *placement,
+		       struct ttm_mem_reg *mem,
+		       uint32_t *new_flags)
 {
 	int i;
 
@@ -1068,6 +1068,7 @@ static bool ttm_bo_mem_compat(struct ttm_placement *placement,
 
 	return false;
 }
+EXPORT_SYMBOL(ttm_bo_mem_compat);
 
 int ttm_bo_validate(struct ttm_buffer_object *bo,
 			struct ttm_placement *placement,

include/drm/ttm/ttm_bo_api.h

@@ -316,6 +316,20 @@ ttm_bo_reference(struct ttm_buffer_object *bo)
  */
 extern int ttm_bo_wait(struct ttm_buffer_object *bo,
 		       bool interruptible, bool no_wait);
+
+/**
+ * ttm_bo_mem_compat - Check if proposed placement is compatible with a bo
+ *
+ * @placement:  Return immediately if buffer is busy.
+ * @mem:  The struct ttm_mem_reg indicating the region where the bo resides
+ * @new_flags: Describes compatible placement found
+ *
+ * Returns true if the placement is compatible
+ */
+extern bool ttm_bo_mem_compat(struct ttm_placement *placement,
+			      struct ttm_mem_reg *mem,
+			      uint32_t *new_flags);
+
 /**
  * ttm_bo_validate
  *