linux-kernel - [PATCH v10 03/10] drm/hdcp: Update property value on content type and user changes

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Message-ID: <20230419154321.1993419-4-markyacoub@google.com>
Date:   Wed, 19 Apr 2023 11:43:13 -0400
From:   Mark Yacoub <markyacoub@...omium.org>
To:     David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Cc:     seanpaul@...omium.org, suraj.kandpal@...el.com,
        dianders@...omium.org, dmitry.baryshkov@...aro.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org,
        Jani Nikula <jani.nikula@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Mark Yacoub <markyacoub@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v10 03/10] drm/hdcp: Update property value on content type and user changes

From: Sean Paul <seanpaul@...omium.org>

Update the connector's property value in 2 cases which were
previously missed:

1- Content type changes. The value should revert back to DESIRED from
   ENABLED in case the driver must re-authenticate the link due to the
   new content type.

2- Userspace sets value to DESIRED while ENABLED. In this case, the
   value should be reset immediately to ENABLED since the link is
   actively being encrypted.

To accommodate these changes, I've split up the conditionals to make
things a bit more clear (as much as one can with this mess of state).

Acked-by: Jani Nikula <jani.nikula@...el.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
Signed-off-by: Sean Paul <seanpaul@...omium.org>
Signed-off-by: Mark Yacoub <markyacoub@...omium.org>

---
Changes in v2:
-None
Changes in v3:
-Fixed indentation issue identified by 0-day
Changes in v4:
-None
Changes in v5:
-None
Changes in v6:
-Rebased: modifications in drm_hdcp_helper.c instead of drm_hdcp.c
Changes in v7:
-Rebased as function name has changed.

 drivers/gpu/drm/display/drm_hdcp_helper.c | 29 +++++++++++++++--------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdcp_helper.c b/drivers/gpu/drm/display/drm_hdcp_helper.c
index 34baf2b97cd87..3ee1a6ae26c53 100644
--- a/drivers/gpu/drm/display/drm_hdcp_helper.c
+++ b/drivers/gpu/drm/display/drm_hdcp_helper.c
@@ -480,21 +480,30 @@ bool drm_hdcp_has_changed(struct drm_connector *connector,
 		return true;
 
 	/*
-	 * Nothing to do if content type is unchanged and one of:
-	 *  - state didn't change
-	 *  - HDCP was activated since the last commit
-	 *  - attempting to set to desired while already enabled
+	 * Content type changes require an HDCP disable/enable cycle.
 	 */
-	if (old_hdcp == new_hdcp ||
-	    (old_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
+	if (new_conn_state->hdcp_content_type !=
+	    old_conn_state->hdcp_content_type) {
+		new_conn_state->content_protection =
+			DRM_MODE_CONTENT_PROTECTION_DESIRED;
+		return true;
+	}
+
+	/*
+	 * Ignore meaningless state changes:
+ 	 *  - HDCP was activated since the last commit
+	 *  - Attempting to set to desired while already enabled
+ 	 */
+	if ((old_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
 	     new_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
 	    (old_hdcp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
 	     new_hdcp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
-		if (old_conn_state->hdcp_content_type ==
-		    new_conn_state->hdcp_content_type)
-			return false;
+		new_conn_state->content_protection =
+			DRM_MODE_CONTENT_PROTECTION_ENABLED;
+		return false;
 	}
 
-	return true;
+	/* Finally, if state changes, we need action */
+	return old_hdcp != new_hdcp;
 }
 EXPORT_SYMBOL(drm_hdcp_has_changed);
-- 
2.40.0.634.g4ca3ef3211-goog