[PATCH] drm/connector: Add doc for content_protection tri-state

[Harry Wentland]

It was there all along in the patch description when this change was
introduced but it would be helpful to have the same documented in the
code.

Signed-off-by: Harry Wentland <harry.wentland at amd.com>
Cc: Sean Paul <seanpaul at chromium.org>
Cc: Sean Paul <sean at poorly.run>
Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
---
 drivers/gpu/drm/drm_connector.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index b34c3d38bf15..c53e51ad3b59 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -1519,6 +1519,15 @@ EXPORT_SYMBOL(drm_connector_attach_scaling_mode_property);
  * Content Protection is intentionally vague to allow for different underlying
  * technologies, however it is most implemented by HDCP.
  *
+ * The property is a tri-state with the following values:
+ * - OFF: Self explanatory, no content protection
+ * - DESIRED: Userspace requests that the driver enable protection
+ * - ENABLED: Once the driver has authenticated the link, it sets this value
+ *
+ * The driver is responsible for downgrading ENABLED to DESIRED if the link becomes
+ * unprotected. The driver should also maintain the desiredness of protection
+ * across hotplug/dpms/suspend.
+ *
  * The content protection will be set to &drm_connector_state.content_protection
  *
  * Returns:
-- 
2.21.0