drm/mode_object: add drm_object_immutable_property_get_value()

We have a helper to get property values for non-atomic drivers and
another one default property values for atomic drivers. In some cases we
need the ability to get value of immutable property, no matter what kind
of driver it is. Implement new property-related helper,
drm_object_immutable_property_get_value(), which lets the caller to get
the value of the immutable property.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260106-drm-fix-lut-checks-v3-1-f7f979eb73c8@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Author: lumag

drivers/gpu/drm/drm_mode_object.c

@@ -385,6 +385,31 @@ int drm_object_property_get_default_value(struct drm_mode_object *obj,
 }
 EXPORT_SYMBOL(drm_object_property_get_default_value);
 
+/**
+ * drm_object_immutable_property_get_value - retrieve the value of a property
+ * @obj: drm mode object to get property value from
+ * @property: property to retrieve
+ * @val: storage for the property value
+ *
+ * This function retrieves the software state of the given immutable property
+ * for the given mode object.
+ *
+ * This function can be called by both atomic and non-atomic drivers.
+ *
+ * Returns:
+ * Zero on success, error code on failure.
+ */
+int drm_object_immutable_property_get_value(struct drm_mode_object *obj,
+					    struct drm_property *property,
+					    uint64_t *val)
+{
+	if (drm_WARN_ON(property->dev, !(property->flags & DRM_MODE_PROP_IMMUTABLE)))
+		return -EINVAL;
+
+	return __drm_object_property_get_prop_value(obj, property, val);
+}
+EXPORT_SYMBOL(drm_object_immutable_property_get_value);
+
 /* helper for getconnector and getproperties ioctls */
 int drm_mode_object_get_properties(struct drm_mode_object *obj, bool atomic,
 				   bool plane_color_pipeline,

include/drm/drm_mode_object.h

@@ -133,6 +133,9 @@ int drm_object_property_get_value(struct drm_mode_object *obj,
 int drm_object_property_get_default_value(struct drm_mode_object *obj,
 					  struct drm_property *property,
 					  uint64_t *val);
+int drm_object_immutable_property_get_value(struct drm_mode_object *obj,
+					    struct drm_property *property,
+					    uint64_t *val);
 
 void drm_object_attach_property(struct drm_mode_object *obj,
 				struct drm_property *property,