release/5.2.38/mei-hdcp-bind-only-with-i915-on-the-same-PCH.patch

From b8e6352a2edaa45efb4744e7e0a5a7621ef509e9 Mon Sep 17 00:00:00 2001
From: Tomas Winkler <tomas.winkler@intel.com>
Date: Thu, 12 Dec 2019 10:41:03 +0200
Subject: [PATCH] mei: hdcp: bind only with i915 on the same PCH

commit 1e8d19d9b0dfcf11b61bac627203a290577e807a upstream.

The mei device and i915 must reside on the same
PCH in order for HDCP to work. Make the component
matching function enforce this requirement.

                   hdcp
                    |
   i915            mei
    |               |
    +----= PCH =----+

Cc: <stable@vger.kernel.org> v5.0+
Cc: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Alexander Usyskin <alexander.usyskin@intel.com>
Link: https://lore.kernel.org/r/20191212084103.2893-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
index b07000202d4a..778f9c4f3281 100644
--- a/drivers/misc/mei/hdcp/mei_hdcp.c
+++ b/drivers/misc/mei/hdcp/mei_hdcp.c
@@ -761,11 +761,38 @@ static const struct component_master_ops mei_component_master_ops = {
 	.unbind = mei_component_master_unbind,
 };
 
+/**
+ * mei_hdcp_component_match - compare function for matching mei hdcp.
+ *
+ *    The function checks if the driver is i915, the subcomponent is HDCP
+ *    and the grand parent of hdcp and the parent of i915 are the same
+ *    PCH device.
+ *
+ * @dev: master device
+ * @subcomponent: subcomponent to match (I915_COMPONENT_HDCP)
+ * @data: compare data (mei hdcp device)
+ *
+ * Return:
+ * * 1 - if components match
+ * * 0 - otherwise
+ */
 static int mei_hdcp_component_match(struct device *dev, int subcomponent,
 				    void *data)
 {
-	return !strcmp(dev->driver->name, "i915") &&
-	       subcomponent == I915_COMPONENT_HDCP;
+	struct device *base = data;
+
+	if (strcmp(dev->driver->name, "i915") ||
+	    subcomponent != I915_COMPONENT_HDCP)
+		return 0;
+
+	base = base->parent;
+	if (!base)
+		return 0;
+
+	base = base->parent;
+	dev = dev->parent;
+
+	return (base && dev && dev == base);
 }
 
 static int mei_hdcp_probe(struct mei_cl_device *cldev,
@@ -789,7 +816,7 @@ static int mei_hdcp_probe(struct mei_cl_device *cldev,
 
 	master_match = NULL;
 	component_match_add_typed(&cldev->dev, &master_match,
-				  mei_hdcp_component_match, comp_master);
+				  mei_hdcp_component_match, &cldev->dev);
 	if (IS_ERR_OR_NULL(master_match)) {
 		ret = -ENOMEM;
 		goto err_exit;
-- 
2.7.4