drm/i915: Add a context open function

We'll be doing a bit more stuff with each file, so having our own open
function should make things clean.

This also allows us to easily add conditionals for stuff we don't want
to do when we don't have HW contexts.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -2225,6 +2225,7 @@ i915_gem_obj_ggtt_pin(struct drm_i915_gem_object *obj,
 /* i915_gem_context.c */
 int __must_check i915_gem_context_init(struct drm_device *dev);
 void i915_gem_context_fini(struct drm_device *dev);
+int i915_gem_context_open(struct drm_device *dev, struct drm_file *file);
 void i915_gem_context_close(struct drm_device *dev, struct drm_file *file);
 int i915_switch_context(struct intel_ring_buffer *ring,
 			struct drm_file *file, int to_id);

drivers/gpu/drm/i915/i915_gem.c

@@ -4859,6 +4859,7 @@ i915_gem_file_idle_work_handler(struct work_struct *work)
 int i915_gem_open(struct drm_device *dev, struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv;
+	int ret;
 
 	DRM_DEBUG_DRIVER("\n");
 
@@ -4874,9 +4875,11 @@ int i915_gem_open(struct drm_device *dev, struct drm_file *file)
 	INIT_DELAYED_WORK(&file_priv->mm.idle_work,
 			  i915_gem_file_idle_work_handler);
 
-	idr_init(&file_priv->context_idr);
+	ret = i915_gem_context_open(dev, file);
+	if (ret)
+		kfree(file_priv);
 
-	return 0;
+	return ret;
 }
 
 static bool mutex_is_locked_by(struct mutex *mutex, struct task_struct *task)

drivers/gpu/drm/i915/i915_gem_context.c

@@ -341,10 +341,25 @@ i915_gem_context_get_hang_stats(struct drm_device *dev,
 	return &ctx->hang_stats;
 }
 
+int i915_gem_context_open(struct drm_device *dev, struct drm_file *file)
+{
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+
+	if (!HAS_HW_CONTEXTS(dev))
+		return 0;
+
+	idr_init(&file_priv->context_idr);
+
+	return 0;
+}
+
 void i915_gem_context_close(struct drm_device *dev, struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 
+	if (!HAS_HW_CONTEXTS(dev))
+		return;
+
 	mutex_lock(&dev->struct_mutex);
 	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
 	idr_destroy(&file_priv->context_idr);