On Thu, Oct 04, 2018 at 08:29:50PM -0400, Lyude Paul wrote:
> With the exception of modesets which would switch the DPMS state of a
> connector from on to off, we want to make sure that we disallow all
> modesets which would result in enabling a new monitor or a new mode
> configuration on a monitor if the connector for the display in question
> is no longer registered. This allows us to stop userspace from trying to
> enable new displays on connectors for an MST topology that were just
> removed from the system, without preventing userspace from disabling
> DPMS on those connectors.
>
> Signed-off-by: Lyude Paul <ly...@redhat.com>
> Cc: sta...@vger.kernel.org
Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch>
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 21 ++++++++++++++++++++-
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> b/drivers/gpu/drm/drm_atomic_helper.c
> index 80be74df7ba6..ce2decfc6826 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -307,6 +307,26 @@ update_connector_routing(struct drm_atomic_state *state,
> return 0;
> }
>
> + crtc_state = drm_atomic_get_new_crtc_state(state,
> + new_connector_state->crtc);
> + /*
> + * For compatibility with legacy users, we want to make sure that
> + * we allow DPMS On->Off modesets on unregistered connectors. Modesets
> + * which would result in anything else must be considered invalid, to
> + * avoid turning on new displays on dead connectors.
> + *
> + * Since the connector can be unregistered at any point during an
> + * atomic check or commit, this is racy. But that's OK: all we care
> + * about is ensuring that userspace can't do anything but shut off the
> + * display on a connector that was destroyed after it's been notified,
> + * not before.
> + */
> + if (!READ_ONCE(connector->registered) && crtc_state->active) {
> + DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] is not registered\n",
> + connector->base.id, connector->name);
> + return -EINVAL;
> + }
> +
> funcs = connector->helper_private;
>
> if (funcs->atomic_best_encoder)
> @@ -351,7 +371,6 @@ update_connector_routing(struct drm_atomic_state *state,
>
> set_best_encoder(state, new_connector_state, new_encoder);
>
> - crtc_state = drm_atomic_get_new_crtc_state(state,
> new_connector_state->crtc);
> crtc_state->connectors_changed = true;
>
> DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on
> [CRTC:%d:%s]\n",
> --
> 2.17.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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