diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 7370c9dfa8a1ce17770399c2dd633e31107bfa52..715b7109c388de5af0017c809b2f101143a61784 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -615,6 +615,14 @@ intel_dp_create_fake_mst_encoder(struct intel_digital_port *intel_dig_port, enum
 	intel_encoder->power_domain = intel_dig_port->base.power_domain;
 	intel_encoder->port = intel_dig_port->base.port;
 	intel_encoder->cloneable = 0;
+	/*
+	 * This is wrong, but broken userspace uses the intersection
+	 * of possible_crtcs of all the encoders of a given connector
+	 * to figure out which crtcs can drive said connector. What
+	 * should be used instead is the union of possible_crtcs.
+	 * To keep such userspace functioning we must misconfigure
+	 * this to make sure the intersection is not empty :(
+	 */
 	intel_encoder->pipe_mask = ~0;
 
 	intel_encoder->compute_config = intel_dp_mst_compute_config;