drm/dp/mst: dump branch OUI in debugfs

From: Dave Airlie <[email protected]>

It appears some MST docks are worse than other, but the only way to know is to see the sw revisions in here, so dump the branch OUI so we can look at the sw revision.

Signed-off-by Dave Airlie <[email protected]>

---
 drivers/gpu/drm/drm_dp_mst_topology.c | 5 +++++
 1 file changed, 5 insertions(+)

drivers/gpu/drm/drm_dp_mst_topology.c +0 -0

index 8a3bfcd..e17a639 100644

Quoted 16 lines · Dave Airlie

From: Dave Airlie <[email protected]>

It appears some MST docks are worse than other, but the only way to know is to see the sw revisions in here, so dump the branch OUI so we can look at the sw revision.

Signed-off-by Dave Airlie <[email protected]>

---
 drivers/gpu/drm/drm_dp_mst_topology.c | 5 +++++
 1 file changed, 5 insertions(+)

drivers/gpu/drm/drm_dp_mst_topology.c +0 -0

index 8a3bfcd..e17a639 100644

drivers/gpu/drm/drm_dp_mst_topology.c void drm_dp_mst_dump_topology(struct seq_file *m, · line 2660

Quoted 4 lines

drivers/gpu/drm/drm_dp_mst_topology.c +1 -0

@@ -2657,6 +2657,11 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
                      seq_printf(m, "%02x ", buf[i]);
              seq_printf(m, "\n");
 
+             ret = drm_dp_dpcd_read(mgr->aux, DP_BRANCH_OUI, buf, DP_RECEIVER_CAP_SIZE);

According to the specification, the OUI is 24-bit, whereas the receiver capability field is 15 bytes (well, at least that is the value defined for DP_RECEIVER_CAP_SIZE)...

drivers/gpu/drm/drm_dp_mst_topology.c void drm_dp_mst_dump_topology(struct seq_file *m, · line 2664

Quoted 4 lines

drivers/gpu/drm/drm_dp_mst_topology.c +4 -0

+             seq_printf(m, "branch oui: ");
+             for (i = 0; i < DP_RECEIVER_CAP_SIZE; i++)
+                     seq_printf(m, "%02x ", buf[i]);
+             seq_printf(m, "\n");

So this will really dump out more than just the OUI. Perhaps it'd be worth splitting that up further? 0x503 to 0x508 is an identification string and displaying it as string would presumably be more useful than the hexdump equivalent. Similarly 0x509 is a hardware revision and 0x50a/0x50b the firmware major/minor version, which might be more readable in an idiomatic format (X.Y).