[PATCH] drm/atomic-helper: relax unregistered connector check

[Lyude Paul]

This seems like a very good solution to the problem :)

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Thu, 2023-10-05 at 13:16 +0000, Simon Ser wrote:
> The driver might pull connectors which weren't submitted by
> user-space into the atomic state. For instance,
> intel_dp_mst_atomic_master_trans_check() pulls in connectors
> sharing the same DP-MST stream. However, if the connector is
> unregistered, this later fails with:
> 
>     [  559.425658] i915 0000:00:02.0: [drm:drm_atomic_helper_check_modeset] [CONNECTOR:378:DP-7] is not registered
> 
> Skip the unregistered connector check to allow user-space to turn
> off connectors one-by-one.
> 
> See this wlroots issue:
> https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3407
> 
> Previous discussion:
> https://lore.kernel.org/intel-gfx/Y6GX7z17WmDSKwta@ideak-desk.fi.intel.com/
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 71d399397107..c9b8343eaa20 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -290,7 +290,8 @@ static int
>  update_connector_routing(struct drm_atomic_state *state,
>  			 struct drm_connector *connector,
>  			 struct drm_connector_state *old_connector_state,
> -			 struct drm_connector_state *new_connector_state)
> +			 struct drm_connector_state *new_connector_state,
> +			 bool added_by_user)
>  {
>  	const struct drm_connector_helper_funcs *funcs;
>  	struct drm_encoder *new_encoder;
> @@ -339,9 +340,13 @@ update_connector_routing(struct drm_atomic_state *state,
>  	 * there's a chance the connector may have been destroyed during the
>  	 * process, but it's better to ignore that then cause
>  	 * drm_atomic_helper_resume() to fail.
> +	 *
> +	 * Last, we want to ignore connector registration when the connector
> +	 * was not pulled in the atomic state by user-space (ie, was pulled
> +	 * in by the driver, e.g. when updating a DP-MST stream).
>  	 */
>  	if (!state->duplicated && drm_connector_is_unregistered(connector) &&
> -	    crtc_state->active) {
> +	    added_by_user && crtc_state->active) {
>  		drm_dbg_atomic(connector->dev,
>  			       "[CONNECTOR:%d:%s] is not registered\n",
>  			       connector->base.id, connector->name);
> @@ -620,7 +625,10 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
>  	struct drm_connector *connector;
>  	struct drm_connector_state *old_connector_state, *new_connector_state;
>  	int i, ret;
> -	unsigned int connectors_mask = 0;
> +	unsigned int connectors_mask = 0, user_connectors_mask = 0;
> +
> +	for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i)
> +		user_connectors_mask |= BIT(i);
>  
>  	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
>  		bool has_connectors =
> @@ -685,7 +693,8 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
>  		 */
>  		ret = update_connector_routing(state, connector,
>  					       old_connector_state,
> -					       new_connector_state);
> +					       new_connector_state,
> +						   BIT(i) & user_connectors_mask);
>  		if (ret)
>  			return ret;
>  		if (old_connector_state->crtc) {

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat