drm/dp/mst: Enhance DP MST debugfs output

Add some additional information (input vs. output port, sink associated
with VC, peer device type, max number of VCs supported) and ensure that
any embedded '\0' characters in a branch device's devid string are not
written to debugfs.

v2: Rebase + change drm_edid_get_monitor_name() call to reflect new
    signature.

v3: Minor changes suggested by Jani + rebase.

v4: Rebase

cc: dri-devel@lists.freedesktop.org
cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJim Bride <jim.bride@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1460654317-31288-2-git-send-email-jim.bride@linux.intel.com

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -2729,7 +2729,7 @@ static void drm_dp_mst_dump_mstb(struct seq_file *m,
 
 	seq_printf(m, "%smst: %p, %d\n", prefix, mstb, mstb->num_ports);
 	list_for_each_entry(port, &mstb->ports, next) {
-		seq_printf(m, "%sport: %d: ddps: %d ldps: %d, sdp: %d/%d, %p, conn: %p\n", prefix, port->port_num, port->ddps, port->ldps, port->num_sdp_streams, port->num_sdp_stream_sinks, port, port->connector);
+		seq_printf(m, "%sport: %d: input: %d: pdt: %d, ddps: %d ldps: %d, sdp: %d/%d, %p, conn: %p\n", prefix, port->port_num, port->input, port->pdt, port->ddps, port->ldps, port->num_sdp_streams, port->num_sdp_stream_sinks, port, port->connector);
 		if (port->mstb)
 			drm_dp_mst_dump_mstb(m, port->mstb);
 	}
@@ -2750,6 +2750,16 @@ static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
 	return false;
 }
 
+static void fetch_monitor_name(struct drm_dp_mst_topology_mgr *mgr,
+			       struct drm_dp_mst_port *port, char *name,
+			       int namelen)
+{
+	struct edid *mst_edid;
+
+	mst_edid = drm_dp_mst_get_edid(port->connector, mgr, port);
+	drm_edid_get_monitor_name(mst_edid, name, namelen);
+}
+
 /**
  * drm_dp_mst_dump_topology(): dump topology to seq file.
  * @m: seq_file to dump output to
@@ -2762,6 +2772,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 {
 	int i;
 	struct drm_dp_mst_port *port;
+
 	mutex_lock(&mgr->lock);
 	if (mgr->mst_primary)
 		drm_dp_mst_dump_mstb(m, mgr->mst_primary);
@@ -2770,14 +2781,21 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 	mutex_unlock(&mgr->lock);
 
 	mutex_lock(&mgr->payload_lock);
-	seq_printf(m, "vcpi: %lx %lx\n", mgr->payload_mask, mgr->vcpi_mask);
+	seq_printf(m, "vcpi: %lx %lx %d\n", mgr->payload_mask, mgr->vcpi_mask,
+		mgr->max_payloads);
 
 	for (i = 0; i < mgr->max_payloads; i++) {
 		if (mgr->proposed_vcpis[i]) {
+			char name[14];
+
 			port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
-			seq_printf(m, "vcpi %d: %d %d %d\n", i, port->port_num, port->vcpi.vcpi, port->vcpi.num_slots);
+			fetch_monitor_name(mgr, port, name, sizeof(name));
+			seq_printf(m, "vcpi %d: %d %d %d sink name: %s\n", i,
+				   port->port_num, port->vcpi.vcpi,
+				   port->vcpi.num_slots,
+				   (*name != 0) ? name :  "Unknown");
 		} else
-			seq_printf(m, "vcpi %d:unsed\n", i);
+			seq_printf(m, "vcpi %d:unused\n", i);
 	}
 	for (i = 0; i < mgr->max_payloads; i++) {
 		seq_printf(m, "payload %d: %d, %d, %d\n",
@@ -2817,8 +2835,9 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 		for (i = 0; i < 0x3; i++)
 			seq_printf(m, "%02x", buf[i]);
 		seq_printf(m, " devid: ");
-		for (i = 0x3; i < 0x8; i++)
+		for (i = 0x3; i < 0x8 && buf[i]; i++)
 			seq_printf(m, "%c", buf[i]);
+
 		seq_printf(m, " revision: hw: %x.%x sw: %x.%x", buf[0x9] >> 4, buf[0x9] & 0xf, buf[0xa], buf[0xb]);
 		seq_printf(m, "\n");
 		bret = dump_dp_payload_table(mgr, buf);