drm: report dp downstream port type as a subconnector property

Currently, downstream port type is only reported in debugfs. This
information should be considered important since it reflects the actual
physical connector type. Some userspace (e.g. window compositors)
may want to show this info to a user.

The 'subconnector' property is already utilized for DVI-I and TV-out for
reporting connector subtype.

The initial motivation for this feature came from i2c test [1].
It is supposed to be skipped on VGA connectors, but it cannot
detect VGA over DP and fails instead.

v2:
 - Ville: utilized drm_dp_is_branch()
 - Ville: implement DP 1.0 downstream type info
 - Replaced create_dp_properties with add_dp_subconnector_property
 - Added dp_set_subconnector_property helper

v4:
 - Ville: add DP1.0 best assumption about subconnector
 - Ville: assume DVI is DVI-D
 - Ville: reuse Writeback enum value for Virtual subconnector
 - Renamed #defines: HDMI -> HDMIA, DP -> DisplayPort

v5: rebase

v6:
 - Jani Nikula: renamed a function name
 - Jani Nikula: addressed the issues with documentation

[1]: https://bugs.freedesktop.org/show_bug.cgi?id=104097

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Jeevan B <jeevan.b@intel.com>
Signed-off-by: Oleg Vasilev <oleg.vasilev@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1587732655-17544-1-git-send-email-jeevan.b@intel.com

1 files changed, 8 insertions, 0 deletions

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index e47dc22ebf50..5c2819924862 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -26,6 +26,7 @@
 #include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/types.h>
+#include <drm/drm_connector.h>
 
 /*
  * Unless otherwise noted, all values are from the DP 1.1a spec.  Note that
@@ -1619,6 +1620,13 @@ int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 int drm_dp_downstream_id(struct drm_dp_aux *aux, char id[6]);
 void drm_dp_downstream_debug(struct seq_file *m, const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 			     const u8 port_cap[4], struct drm_dp_aux *aux);
+enum drm_mode_subconnector
+drm_dp_subconnector_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+			 const u8 port_cap[4]);
+void drm_dp_set_subconnector_property(struct drm_connector *connector,
+				      enum drm_connector_status status,
+				      const u8 *dpcd,
+				      const u8 port_cap[4]);
 
 void drm_dp_remote_aux_init(struct drm_dp_aux *aux);
 void drm_dp_aux_init(struct drm_dp_aux *aux);