[PATCH v4 06/11] drm: Read DP branch device id

[Mika Kahola]

Read DisplayPort branch device id string.

Signed-off-by: Mika Kahola <mika.kahola at intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 12 ++++++++++++
 include/drm/drm_dp_helper.h     |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index bac0ccc..c25bed9 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -538,6 +538,18 @@ int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 }
 EXPORT_SYMBOL(drm_dp_downstream_max_bpc);
 
+/**
+ * drm_dp_downstream_id() - identify branch device
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns branch device id on success or NULL on failure
+ */
+int drm_dp_downstream_id(struct drm_dp_aux *aux, char id[6])
+{
+	return drm_dp_dpcd_read(aux, DP_BRANCH_ID, id, 6);
+}
+EXPORT_SYMBOL(drm_dp_downstream_id);
+
 /*
  * I2C-over-AUX implementation
  */
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index d4abc38..37293a8 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -445,6 +445,7 @@
 #define DP_SOURCE_OUI			    0x300
 #define DP_SINK_OUI			    0x400
 #define DP_BRANCH_OUI			    0x500
+#define DP_BRANCH_ID                        0x503
 
 #define DP_SET_POWER                        0x600
 # define DP_SET_POWER_D0                    0x1
@@ -814,6 +815,7 @@ int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
                                 const u8 port_cap[4]);
 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
                               const u8 port_cap[4]);
+int drm_dp_downstream_id(struct drm_dp_aux *aux, char id[6]);
 
 int drm_dp_aux_register(struct drm_dp_aux *aux);
 void drm_dp_aux_unregister(struct drm_dp_aux *aux);
-- 
1.9.1