[PATCH v4 06/15] mei: pxp: support matching with a gfx discrete card

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

From: Tomas Winkler <tomas.winkler@intel.com>

With on-boards graphics card, both i915 and MEI
are in the same device hierarchy with the same parent,
while for discrete gfx card the MEI is its child device.
Adjust the match function for that scenario
by matching MEI parent device with i915.

V2:
 1. More detailed commit message
 2. Check for dev is not null before it is accessed.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Vitaly Lubart <vitaly.lubart@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
---
 drivers/misc/mei/pxp/mei_pxp.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/mei/pxp/mei_pxp.c b/drivers/misc/mei/pxp/mei_pxp.c
index 17c5d201603f..afc047627800 100644
--- a/drivers/misc/mei/pxp/mei_pxp.c
+++ b/drivers/misc/mei/pxp/mei_pxp.c
@@ -159,17 +159,24 @@ static int mei_pxp_component_match(struct device *dev, int subcomponent,
 {
 	struct device *base = data;
 
+	if (!dev)
+		return 0;
+
 	if (!dev->driver || strcmp(dev->driver->name, "i915") ||
 	    subcomponent != I915_COMPONENT_PXP)
 		return 0;
 
 	base = base->parent;
-	if (!base)
+	if (!base) /* mei device */
 		return 0;
 
-	base = base->parent;
-	dev = dev->parent;
+	base = base->parent; /* pci device */
+	/* for dgfx */
+	if (base && dev == base)
+		return 1;
 
+	/* for pch */
+	dev = dev->parent;
 	return (base && dev && dev == base);
 }
 
-- 
2.37.2