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Subject[PATCH 5.4 022/110] mei: hdcp: bind only with i915 on the same PCH
Date
From: Tomas Winkler <tomas.winkler@intel.com>

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>

---
drivers/misc/mei/hdcp/mei_hdcp.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)

--- a/drivers/misc/mei/hdcp/mei_hdcp.c
+++ b/drivers/misc/mei/hdcp/mei_hdcp.c
@@ -758,11 +758,38 @@ static const struct 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,
@@ -786,7 +813,7 @@ static int mei_hdcp_probe(struct mei_cl_

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;

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