[PATCH v2 13/14] drm: Validate encoder->possible_clones

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Many drivers are populating encoder->possible_clones wrong. Let's
persuade them to get it right by adding some loud WARNs.

We'll cross check the bits between any two encoders. So either
both encoders can clone with the other, or neither can.

We'll also complain about effectively empty possible_clones, and
possible_clones containing bits for encoders that don't exist.

TODO: Or should we just silently filter out any bits for non-existing
encoders?

v2: encoder->possible_clones now includes the encoder itelf

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_encoder.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
index e87e6fecc1fb..3ece97a9d029 100644
--- a/drivers/gpu/drm/drm_encoder.c
+++ b/drivers/gpu/drm/drm_encoder.c
@@ -78,6 +78,34 @@ static void fixup_possible_clones(struct drm_device *dev)
 		encoder->possible_clones |= drm_encoder_mask(encoder);
 }
 
+static void validate_possible_clones(struct drm_encoder *encoder)
+{
+	struct drm_device *dev = encoder->dev;
+	struct drm_encoder *other;
+	u32 encoder_mask = 0;
+
+	drm_for_each_encoder(other, dev) {
+		encoder_mask |= drm_encoder_mask(other);
+
+		WARN(!(encoder->possible_clones & drm_encoder_mask(other)) !=
+		     !(other->possible_clones & drm_encoder_mask(encoder)),
+		     "possible_clones mismatch: "
+		     "[ENCODER:%d:%s] mask=0x%x possible_clones=0x%x vs. "
+		     "[ENCODER:%d:%s] mask=0x%x possible_clones=0x%x\n",
+		     encoder->base.id, encoder->name,
+		     drm_encoder_mask(encoder), encoder->possible_clones,
+		     other->base.id, other->name,
+		     drm_encoder_mask(other), other->possible_clones);
+	}
+
+	WARN((encoder->possible_clones & drm_encoder_mask(encoder)) == 0 ||
+	     (encoder->possible_clones & ~encoder_mask) != 0,
+	     "Bogus possible_clones: "
+	     "[ENCODER:%d:%s] possible_clones=0x%x (full encoder mask=0x%x)\n",
+	     encoder->base.id, encoder->name,
+	     encoder->possible_clones, encoder_mask);
+}
+
 int drm_encoder_register_all(struct drm_device *dev)
 {
 	struct drm_encoder *encoder;
@@ -86,6 +114,8 @@ int drm_encoder_register_all(struct drm_device *dev)
 	fixup_possible_clones(dev);
 
 	drm_for_each_encoder(encoder, dev) {
+		validate_possible_clones(encoder);
+
 		if (encoder->funcs->late_register)
 			ret = encoder->funcs->late_register(encoder);
 		if (ret)
-- 
2.21.0