[PATCH] drm/atomic-helper: Reject attempts at re-stealing encoders

[PATCH] drm/atomic-helper: Reject attempts at re-stealing encoders

[Daniel Vetter]

This can happen when we run out of encoders for a multi-crtc modeset,
or also when userspace is silly and tries to clone multiple connectors
that need the same encoder on the same crtc.

Reported-and-Tested-and-Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index d6d80b30f751..aff616dc6caf 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -86,6 +86,27 @@ drm_atomic_helper_plane_changed(struct drm_atomic_state *state,
 	}
 }
 
+static bool
+check_pending_encoder_assignment(struct drm_atomic_state *state,
+				 struct drm_encoder *new_encoder,
+				 struct drm_connector *new_connector)
+{
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	int i;
+
+	for_each_connector_in_state(state, connector, conn_state, i) {
+		if (conn_state->best_encoder != new_encoder)
+			continue;
+
+		/* encoder already assigned and we're trying to re-steal it! */
+		if (connector->state->best_encoder != conn_state->best_encoder)
+			return false;
+	}
+
+	return true;
+}
+
 static struct drm_crtc *
 get_current_crtc_for_encoder(struct drm_device *dev,
 			     struct drm_encoder *encoder)
@@ -235,6 +256,13 @@ update_connector_routing(struct drm_atomic_state *state, int conn_idx)
 		return 0;
 	}
 
+	if (!check_pending_encoder_assignment(state, new_encoder, connector)) {
+		DRM_DEBUG_ATOMIC("Encoder for [CONNECTOR:%d:%s] already assigned\n",
+				 connector->base.id,
+				 connector->name);
+		return -EINVAL;
+	}
+
 	encoder_crtc = get_current_crtc_for_encoder(state->dev,
 						    new_encoder);
 
-- 
2.5.1

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Re: [PATCH] drm/atomic-helper: Reject attempts at re-stealing encoders

[Daniel Vetter]

On Thu, Dec 03, 2015 at 10:49:14AM +0100, Daniel Vetter wrote:
> This can happen when we run out of encoders for a multi-crtc modeset,
> or also when userspace is silly and tries to clone multiple connectors
> that need the same encoder on the same crtc.
> 
> Reported-and-Tested-and-Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

And also pulled into drm-misc, it prevents fireworks on i915 with
Maarten's latest atomic work.
-Daniel

> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index d6d80b30f751..aff616dc6caf 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -86,6 +86,27 @@ drm_atomic_helper_plane_changed(struct drm_atomic_state *state,
>  	}
>  }
>  
> +static bool
> +check_pending_encoder_assignment(struct drm_atomic_state *state,
> +				 struct drm_encoder *new_encoder,
> +				 struct drm_connector *new_connector)
> +{
> +	struct drm_connector *connector;
> +	struct drm_connector_state *conn_state;
> +	int i;
> +
> +	for_each_connector_in_state(state, connector, conn_state, i) {
> +		if (conn_state->best_encoder != new_encoder)
> +			continue;
> +
> +		/* encoder already assigned and we're trying to re-steal it! */
> +		if (connector->state->best_encoder != conn_state->best_encoder)
> +			return false;
> +	}
> +
> +	return true;
> +}
> +
>  static struct drm_crtc *
>  get_current_crtc_for_encoder(struct drm_device *dev,
>  			     struct drm_encoder *encoder)
> @@ -235,6 +256,13 @@ update_connector_routing(struct drm_atomic_state *state, int conn_idx)
>  		return 0;
>  	}
>  
> +	if (!check_pending_encoder_assignment(state, new_encoder, connector)) {
> +		DRM_DEBUG_ATOMIC("Encoder for [CONNECTOR:%d:%s] already assigned\n",
> +				 connector->base.id,
> +				 connector->name);
> +		return -EINVAL;
> +	}
> +
>  	encoder_crtc = get_current_crtc_for_encoder(state->dev,
>  						    new_encoder);
>  
> -- 
> 2.5.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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