[PATCH] drm/doc: describe PATH format for DP MST

[Simon Ser]

This is already uAPI, xserver parses it. It's useful to document
since user-space might want to lookup the parent connector.

Additionally, people (me included) have misunderstood the PATH
property for being stable across reboots, but since a KMS object
ID is baked in there that's not the case. So PATH shouldn't be
used as-is in config files and such.

Signed-off-by: Simon Ser <contact at emersion.fr>
Cc: Pekka Paalanen <pekka.paalanen at collabora.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/drm_connector.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index c3725086f413..392bec1355a3 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -1198,6 +1198,11 @@ static const u32 dp_colorspaces =
  * 	drm_connector_set_path_property(), in the case of DP MST with the
  * 	path property the MST manager created. Userspace cannot change this
  * 	property.
+ *
+ * 	In the case of DP MST, the property has the format
+ * 	``mst:<parent>-<ports>`` where ``<parent>`` is the KMS object ID of the
+ * 	parent connector and ``<ports>`` is a hyphen-separated list of DP MST
+ * 	port numbers. Note, KMS object IDs are not stable across reboots.
  * TILE:
  * 	Connector tile group property to indicate how a set of DRM connector
  * 	compose together into one logical screen. This is used by both high-res
-- 
2.42.0