[RFC 09/20] drm/i915/dp: Extract drm_dp_has_mst()

[Lyude Paul]

Just a tiny drive-by cleanup, we can consolidate i915's code for
checking for MST support into a helper to be shared across drivers.

Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 18 ++----------------
 include/drm/drm_dp_mst_helper.h         | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 79c27f91f42c0..1e29d3a012856 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4699,20 +4699,6 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 	return true;
 }
 
-static bool
-intel_dp_sink_can_mst(struct intel_dp *intel_dp)
-{
-	u8 mstm_cap;
-
-	if (intel_dp->dpcd[DP_DPCD_REV] < 0x12)
-		return false;
-
-	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_MSTM_CAP, &mstm_cap) != 1)
-		return false;
-
-	return mstm_cap & DP_MST_CAP;
-}
-
 static bool
 intel_dp_can_mst(struct intel_dp *intel_dp)
 {
@@ -4720,7 +4706,7 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
 
 	return i915->params.enable_dp_mst &&
 		intel_dp->can_mst &&
-		intel_dp_sink_can_mst(intel_dp);
+		drm_dp_has_mst(&intel_dp->aux, intel_dp->dpcd);
 }
 
 static void
@@ -4729,7 +4715,7 @@ intel_dp_configure_mst(struct intel_dp *intel_dp)
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	struct intel_encoder *encoder =
 		&dp_to_dig_port(intel_dp)->base;
-	bool sink_can_mst = intel_dp_sink_can_mst(intel_dp);
+	bool sink_can_mst = drm_dp_has_mst(&intel_dp->aux, intel_dp->dpcd);
 
 	drm_dbg_kms(&i915->drm,
 		    "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s\n",
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 8b9eb4db3381c..2d8983a713e8c 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -911,4 +911,26 @@ __drm_dp_mst_state_iter_get(struct drm_atomic_state *state,
 	for ((__i) = 0; (__i) < (__state)->num_private_objs; (__i)++) \
 		for_each_if(__drm_dp_mst_state_iter_get((__state), &(mgr), NULL, &(new_state), (__i)))
 
+/**
+ * drm_dp_has_mst() - check whether or not a sink supports MST
+ * @aux: The DP AUX channel to use
+ * @dpcd: A cached copy of the DPCD capabilities for this sink
+ *
+ * Returns: %True if the sink supports MST, %false otherwise
+ */
+static inline bool
+drm_dp_has_mst(struct drm_dp_aux *aux,
+	       const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	u8 mstm_cap;
+
+	if (dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
+		return false;
+
+	if (drm_dp_dpcd_readb(aux, DP_MSTM_CAP, &mstm_cap) != 1)
+		return false;
+
+	return !!(mstm_cap & DP_MST_CAP);
+}
+
 #endif
-- 
2.26.2