From e201878b936eefc7ebdab9d30198e2584e5b5617 Mon Sep 17 00:00:00 2001
From: Frederik Gladhorn <frederik.gladhorn@qt.io>
Date: Wed, 1 Aug 2018 22:29:05 +0200
Subject: [PATCH] Fix manufacturer parsing from EDID

The code was quite dubious, in the edid data, the manufacturer is
encoded with a three letter shortcut. In addition it can be set by the
extra data strings, which is not often the case. We would randomly
overwrite the identifier string, so clearly separate the pnpId (3 letter
ID) out and use the fallback table we have.
Also looking up the manufacturer string twice is pointless (contains and
then operator[]).

Change-Id: I18882a78d69b9f3dfc2af31e646ded44f2b70a50
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
---
 src/platformsupport/edid/qedidparser.cpp | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/src/platformsupport/edid/qedidparser.cpp b/src/platformsupport/edid/qedidparser.cpp
index 1cc16b47f8..ccaa50704c 100644
--- a/src/platformsupport/edid/qedidparser.cpp
+++ b/src/platformsupport/edid/qedidparser.cpp
@@ -100,11 +100,11 @@ bool QEdidParser::parse(const QByteArray &blob)
      * 7654321076543210
      * |\---/\---/\---/
      * R  C1   C2   C3 */
-    char id[3];
-    id[0] = 'A' + ((data[EDID_OFFSET_PNP_ID] & 0x7c) / 4) - 1;
-    id[1] = 'A' + ((data[EDID_OFFSET_PNP_ID] & 0x3) * 8) + ((data[EDID_OFFSET_PNP_ID + 1] & 0xe0) / 32) - 1;
-    id[2] = 'A' + (data[EDID_OFFSET_PNP_ID + 1] & 0x1f) - 1;
-    identifier = QString::fromLatin1(id, 3);
+    char pnpId[3];
+    pnpId[0] = 'A' + ((data[EDID_OFFSET_PNP_ID] & 0x7c) / 4) - 1;
+    pnpId[1] = 'A' + ((data[EDID_OFFSET_PNP_ID] & 0x3) * 8) + ((data[EDID_OFFSET_PNP_ID + 1] & 0xe0) / 32) - 1;
+    pnpId[2] = 'A' + (data[EDID_OFFSET_PNP_ID + 1] & 0x1f) - 1;
+    QString pnpIdString = QString::fromLatin1(pnpId, 3);
 
     // Clear manufacturer
     manufacturer = QString();
@@ -136,12 +136,11 @@ bool QEdidParser::parse(const QByteArray &blob)
     }
 
     // Try to use cache first because it is potentially more updated
-    if (m_vendorCache.contains(identifier)) {
-        manufacturer = m_vendorCache[identifier];
-    } else {
+    manufacturer = m_vendorCache.value(pnpIdString);
+    if (manufacturer.isEmpty()) {
         // Find the manufacturer from the vendor lookup table
         for (size_t i = 0; i < ARRAY_LENGTH(q_edidVendorTable); i++) {
-            if (strcmp(q_edidVendorTable[i].id, identifier.toLatin1().constData()) == 0) {
+            if (strncmp(q_edidVendorTable[i].id, pnpId, 3) == 0) {
                 manufacturer = QString::fromUtf8(q_edidVendorTable[i].name);
                 break;
             }
@@ -150,7 +149,7 @@ bool QEdidParser::parse(const QByteArray &blob)
 
     // If we don't know the manufacturer, fallback to PNP ID
     if (manufacturer.isEmpty())
-        manufacturer = identifier;
+        manufacturer = pnpIdString;
 
     // Physical size
     physicalSize = QSizeF(data[EDID_PHYSICAL_WIDTH], data[EDID_OFFSET_PHYSICAL_HEIGHT]) * 10;