From e38e12895022d7148220fc35782b5bd6461f1736 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Wed, 12 Jul 2017 18:52:54 +0300
Subject: [PATCH] drm/dp/mst: Use memchr_inv() instead of memcmp() against a zeroed array
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Git-commit: e38e12895022d7148220fc35782b5bd6461f1736
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

We have memch_inv(), so no need to memcmp() against a zeroed temp array.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170712155254.26455-1-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |   18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1344,15 +1344,17 @@ static void drm_dp_mst_link_probe_work(s
 static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
 				 u8 *guid)
 {
-	static u8 zero_guid[16];
+	u64 salt;
 
-	if (!memcmp(guid, zero_guid, 16)) {
-		u64 salt = get_jiffies_64();
-		memcpy(&guid[0], &salt, sizeof(u64));
-		memcpy(&guid[8], &salt, sizeof(u64));
-		return false;
-	}
-	return true;
+	if (memchr_inv(guid, 0, 16))
+		return true;
+
+	salt = get_jiffies_64();
+
+	memcpy(&guid[0], &salt, sizeof(u64));
+	memcpy(&guid[8], &salt, sizeof(u64));
+
+	return false;
 }
 
 #if 0