drm: Do not set connector->encoder in drivers
An encoder is associated with a connector by the DRM core as a result of
setting up a configuration. Drivers using the atomic or legacy helpers
should never set up this link, even if it is a static one.
While at it, try to catch this kind of error in the future by adding a
WARN_ON() in drm_mode_connector_attach_encoder(). Note that this doesn't
cover all the cases, since drivers could set this up after attaching.
Drivers that use the atomic helpers will get a warning later on, though,
so hopefully the two combined cover enough to help people avoid this in
the future.
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: Mark yao <mark.yao@rock-chips.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1447694393-24700-1-git-send-email-thierry.reding@gmail.com
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 62fa95f..d40bab2 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -5054,6 +5054,20 @@
{
int i;
+ /*
+ * In the past, drivers have attempted to model the static association
+ * of connector to encoder in simple connector/encoder devices using a
+ * direct assignment of connector->encoder = encoder. This connection
+ * is a logical one and the responsibility of the core, so drivers are
+ * expected not to mess with this.
+ *
+ * Note that the error return should've been enough here, but a large
+ * majority of drivers ignores the return value, so add in a big WARN
+ * to get people's attention.
+ */
+ if (WARN_ON(connector->encoder))
+ return -EINVAL;
+
for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
if (connector->encoder_ids[i] == 0) {
connector->encoder_ids[i] = encoder->base.id;