drm/i915/mst: Document the userspace fail with possible_crtcs (29b27657) · Commits · 戴 / test

To avoid accidentally breaking things in the future add a comment explaining why we misconfigure the pipe_mask. Also toss in a TODO for investigating a single encoder approach as opposed to the encoder-per-pipe approach. v2: Drop a bogus TODO comment Signed-off-by:

Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191002162505.30716-6-ville.syrjala@linux.intel.com Reviewed-by:

Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>

drivers/gpu/drm/i915/display/intel_dp_mst.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -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;

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