drm: allow property validation for refcnted props

We can already have object properties, which technically can be fb's.
Switch the property validation logic over to a get/put style interface
so it can take a ref to refcnt'd objects, and then drop that ref after
the driver has a chance to take it's own ref.

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 5213da4..5ee4b88 100644 (file)
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -4193,12 +4193,22 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
 
-static bool drm_property_change_is_valid(struct drm_property *property,
-                                        uint64_t value)
+/* Some properties could refer to dynamic refcnt'd objects, or things that
+ * need special locking to handle lifetime issues (ie. to ensure the prop
+ * value doesn't become invalid part way through the property update due to
+ * race).  The value returned by reference via 'obj' should be passed back
+ * to drm_property_change_valid_put() after the property is set (and the
+ * object to which the property is attached has a chance to take it's own
+ * reference).
+ */
+static bool drm_property_change_valid_get(struct drm_property *property,
+                                        uint64_t value, struct drm_mode_object **ref)
 {
        if (property->flags & DRM_MODE_PROP_IMMUTABLE)
                return false;
 
+       *ref = NULL;
+
        if (drm_property_type_is(property, DRM_MODE_PROP_RANGE)) {
                if (value < property->values[0] || value > property->values[1])
                        return false;
@@ -4219,19 +4229,23 @@ static bool drm_property_change_is_valid(struct drm_property *property,
                /* Only the driver knows */
                return true;
        } else if (drm_property_type_is(property, DRM_MODE_PROP_OBJECT)) {
-               struct drm_mode_object *obj;
                /* a zero value for an object property translates to null: */
                if (value == 0)
                        return true;
-               /*
-                * NOTE: use _object_find() directly to bypass restriction on
-                * looking up refcnt'd objects (ie. fb's).  For a refcnt'd
-                * object this could race against object finalization, so it
-                * simply tells us that the object *was* valid.  Which is good
-                * enough.
-                */
-               obj = _object_find(property->dev, value, property->values[0]);
-               return obj != NULL;
+
+               /* handle refcnt'd objects specially: */
+               if (property->values[0] == DRM_MODE_OBJECT_FB) {
+                       struct drm_framebuffer *fb;
+                       fb = drm_framebuffer_lookup(property->dev, value);
+                       if (fb) {
+                               *ref = &fb->base;
+                               return true;
+                       } else {
+                               return false;
+                       }
+               } else {
+                       return _object_find(property->dev, value, property->values[0]) != NULL;
+               }
        } else {
                int i;
                for (i = 0; i < property->num_values; i++)
@@ -4241,6 +4255,18 @@ static bool drm_property_change_is_valid(struct drm_property *property,
        }
 }
 
+static void drm_property_change_valid_put(struct drm_property *property,
+               struct drm_mode_object *ref)
+{
+       if (!ref)
+               return;
+
+       if (drm_property_type_is(property, DRM_MODE_PROP_OBJECT)) {
+               if (property->values[0] == DRM_MODE_OBJECT_FB)
+                       drm_framebuffer_unreference(obj_to_fb(ref));
+       }
+}
+
 /**
  * drm_mode_connector_property_set_ioctl - set the current value of a connector property
  * @dev: DRM device
@@ -4429,8 +4455,8 @@ int drm_mode_obj_set_property_ioctl(struct drm_device *dev, void *data,
        struct drm_mode_object *arg_obj;
        struct drm_mode_object *prop_obj;
        struct drm_property *property;
-       int ret = -EINVAL;
-       int i;
+       int i, ret = -EINVAL;
+       struct drm_mode_object *ref;
 
        if (!drm_core_check_feature(dev, DRIVER_MODESET))
                return -EINVAL;
@@ -4460,7 +4486,7 @@ int drm_mode_obj_set_property_ioctl(struct drm_device *dev, void *data,
        }
        property = obj_to_property(prop_obj);
 
-       if (!drm_property_change_is_valid(property, arg->value))
+       if (!drm_property_change_valid_get(property, arg->value, &ref))
                goto out;
 
        switch (arg_obj->type) {
@@ -4477,6 +4503,8 @@ int drm_mode_obj_set_property_ioctl(struct drm_device *dev, void *data,
                break;
        }
 
+       drm_property_change_valid_put(property, ref);
+
 out:
        drm_modeset_unlock_all(dev);
        return ret;