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

Daniel Vetter
2015-12-03T09:49:14Z

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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