[PATCH 3/3] drm/atomic: Refuse to steal encoders from connectors not part of the state.

[Daniel Vetter]

On Thu, Feb 18, 2016 at 09:54:43AM +0100, Maarten Lankhorst wrote:
> Because encoder <-> connector mapping is fixed when not moving to
> another crtc we can just reject connectors trying to steal an encoder
> from a connector not part of the state. This won't break MST on i915
> because in that case connectors will be part of the state if you switch
> them between crtc's. If they're not they stay on the same crtc, and
> encoder stealing would have failed anyway.

We must do this for backwards compat. setCrtc on a connector that needs an
encoder already used on some other crtc is supposed to disable that
encoder (and the entire pipe if it's all unused) if we need it.
-Daniel

> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 43 +++++++++++++++++--------------------
>  1 file changed, 20 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index fa708559542c..b2028d592483 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -92,14 +92,21 @@ check_pending_encoder_assignment(struct drm_atomic_state *state,
>  				 int conn_idx)
>  {
>  	struct drm_connector *connector;
> -	struct drm_connector_state *conn_state;
> -	int i;
>  
> -	for_each_connector_in_state(state, connector, conn_state, i) {
> -		if (i >= conn_idx)
> -			break;
> +	drm_for_each_connector(connector, state->dev) {
> +		struct drm_connector_state *conn_state =
> +			drm_atomic_get_existing_connector_state(state,
> +								connector);
>  
> -		if (conn_state->best_encoder == new_encoder)
> +		if (!conn_state) {
> +			if (connector->state->best_encoder == new_encoder)
> +				return false;
> +
> +			continue;
> +		}
> +
> +		if (drm_connector_index(connector) < conn_idx &&
> +		    conn_state->best_encoder == new_encoder)
>  			return false;
>  	}
>  
> @@ -149,29 +156,19 @@ set_best_encoder(struct drm_atomic_state *state,
>  
>  static int
>  steal_encoder(struct drm_atomic_state *state,
> -	      struct drm_encoder *encoder)
> +	      struct drm_encoder *encoder,
> +	      int conn_idx)
>  {
> -	struct drm_mode_config *config = &state->dev->mode_config;
>  	struct drm_crtc_state *crtc_state;
>  	struct drm_connector *connector;
>  	struct drm_connector_state *connector_state;
> +	int i;
>  
> -	/*
> -	 * We can only steal an encoder coming from a connector, which means we
> -	 * must already hold the connection_mutex.
> -	 */
> -	WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
> -
> -	list_for_each_entry(connector, &config->connector_list, head) {
> +	for_each_connector_in_state(state, connector, connector_state, i) {
>  		struct drm_crtc *encoder_crtc;
>  
> -		if (connector->state->best_encoder != encoder)
> -			continue;
> -
> -		connector_state = drm_atomic_get_connector_state(state,
> -								 connector);
> -		if (IS_ERR(connector_state))
> -			return PTR_ERR(connector_state);
> +		if (i >= conn_idx)
> +			break;
>  
>  		if (connector_state->best_encoder != encoder ||
>  		    WARN_ON(!connector_state->crtc))
> @@ -279,7 +276,7 @@ update_connector_routing(struct drm_atomic_state *state,
>  		return -EINVAL;
>  	}
>  
> -	ret = steal_encoder(state, new_encoder);
> +	ret = steal_encoder(state, new_encoder, conn_idx);
>  	if (ret) {
>  		DRM_DEBUG_ATOMIC("Encoder stealing failed for [CONNECTOR:%d:%s]\n",
>  				 connector->base.id,
> -- 
> 2.1.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch