drm/i915: Add intel_crtc_cursor_set_obj() to set cursor buffer (v2)

Refactor cursor buffer setting such that the code to actually update the
cursor lives in a new function, intel_crtc_cursor_set_obj(), and takes
a GEM object as a parameter.  The existing legacy cursor ioctl handler,
intel_crtc_cursor_set() will now perform the userspace handle lookup and
then call this new function.

This refactoring is in preparation for the universal plane cursor
support where we'll want to update the cursor with an actual GEM buffer
object (obtained via drm_framebuffer) rather than a userspace handle.

v2:  Drop obvious kerneldoc and replace with note about function's
     reference consumption
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Pallavi G<pallavi.g@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -8089,21 +8089,26 @@ static void intel_crtc_update_cursor(struct drm_crtc *crtc,
 	intel_crtc->cursor_base = base;
 }
 
-static int intel_crtc_cursor_set(struct drm_crtc *crtc,
-				 struct drm_file *file,
-				 uint32_t handle,
-				 uint32_t width, uint32_t height)
+/*
+ * intel_crtc_cursor_set_obj - Set cursor to specified GEM object
+ *
+ * Note that the object's reference will be consumed if the update fails.  If
+ * the update succeeds, the reference of the old object (if any) will be
+ * consumed.
+ */
+static int intel_crtc_cursor_set_obj(struct drm_crtc *crtc,
+				     struct drm_i915_gem_object *obj,
+				     uint32_t width, uint32_t height)
 {
 	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-	struct drm_i915_gem_object *obj;
 	unsigned old_width;
 	uint32_t addr;
 	int ret;
 
 	/* if we want to turn off the cursor ignore width and height */
-	if (!handle) {
+	if (!obj) {
 		DRM_DEBUG_KMS("cursor off\n");
 		addr = 0;
 		obj = NULL;
@@ -8119,12 +8124,8 @@ static int intel_crtc_cursor_set(struct drm_crtc *crtc,
 		return -EINVAL;
 	}
 
-	obj = to_intel_bo(drm_gem_object_lookup(dev, file, handle));
-	if (&obj->base == NULL)
-		return -ENOENT;
-
 	if (obj->base.size < width * height * 4) {
-		DRM_DEBUG_KMS("buffer is to small\n");
+		DRM_DEBUG_KMS("buffer is too small\n");
 		ret = -ENOMEM;
 		goto fail;
 	}
@@ -8207,6 +8208,25 @@ static int intel_crtc_cursor_set(struct drm_crtc *crtc,
 	return ret;
 }
 
+static int intel_crtc_cursor_set(struct drm_crtc *crtc,
+				 struct drm_file *file,
+				 uint32_t handle,
+				 uint32_t width, uint32_t height)
+{
+	struct drm_device *dev = crtc->dev;
+	struct drm_i915_gem_object *obj;
+
+	if (handle) {
+		obj = to_intel_bo(drm_gem_object_lookup(dev, file, handle));
+		if (&obj->base == NULL)
+			return -ENOENT;
+	} else {
+		obj = NULL;
+	}
+
+	return intel_crtc_cursor_set_obj(crtc, obj, width, height);
+}
+
 static int intel_crtc_cursor_move(struct drm_crtc *crtc, int x, int y)
 {
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);