[PATCH 08/14] 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?

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_encoder.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
index ad13c9cf4312..1c289b227bbc 100644
--- a/drivers/gpu/drm/drm_encoder.c
+++ b/drivers/gpu/drm/drm_encoder.c
@@ -76,12 +76,45 @@ static u32 encoder_possible_clones(struct drm_encoder *encoder)
 		return drm_encoder_mask(encoder);
 }
 
+static void validate_possible_clones(struct drm_encoder *encoder)
+{
+	u32 possible_clones = encoder_possible_clones(encoder);
+	struct drm_device *dev = encoder->dev;
+	struct drm_encoder *other;
+	u32 encoder_mask = 0;
+
+	drm_for_each_encoder(other, dev) {
+		u32 other_possible_clones = encoder_possible_clones(other);
+
+		encoder_mask |= drm_encoder_mask(other);
+
+		WARN(!(possible_clones & drm_encoder_mask(other)) !=
+		     !(other_possible_clones & drm_encoder_mask(encoder)),
+		     "possible_clones mismatch: "
+		     "[ENCODER:%d:%s] index=%d, possible_clones=0x%x vs. "
+		     "[ENCODER:%d:%s] index=%d possible_clones=0x%x\n",
+		     encoder->base.id, encoder->name,
+		     drm_encoder_index(encoder), possible_clones,
+		     other->base.id, other->name,
+		     drm_encoder_index(other), other_possible_clones);
+	}
+
+	WARN((possible_clones & drm_encoder_mask(encoder)) == 0 ||
+	     (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,
+	     possible_clones, encoder_mask);
+}
+
 int drm_encoder_register_all(struct drm_device *dev)
 {
 	struct drm_encoder *encoder;
 	int ret = 0;
 
 	drm_for_each_encoder(encoder, dev) {
+		validate_possible_clones(encoder);
+
 		if (encoder->funcs->late_register)
 			ret = encoder->funcs->late_register(encoder);
 		if (ret)
-- 
2.16.4