From f9854d272c816ca2ad2fec085e17c6591721bff9 Mon Sep 17 00:00:00 2001
From: Gil Dekel <gildekel@google.com>
Date: Thu, 14 Nov 2024 14:14:25 -0500
Subject: SF: Hash and cache descriptor block serial number

More EDID fields are required as a part of migrating to EDID-based
display IDs. This CL parses the device's serial number from the serial
number descriptor bloc, (depicted by the FF marker), hashes it using a
stable hash, and serves it as a part of the Edid struct.

Later, amongst others, this value will be used to fabricate a unique
display ID that is based on the display's EDID.

See:
1. EDID spec: https://glenwing.github.io/docs/VESA-EEDID-A2.pdf
2. https://en.wikipedia.org/wiki/Extended_Display_Identification_Data#Structure,_version_1.4

Flag: com.android.graphics.surfaceflinger.flags.stable_edid_ids
Bug: 378923759
Test: DisplayIdentification_test
Change-Id: If9c9358b0d0850337496740d15419fd0ed330a02
---
 libs/ui/DisplayIdentification.cpp | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

(limited to 'libs/ui/DisplayIdentification.cpp')

diff --git a/libs/ui/DisplayIdentification.cpp b/libs/ui/DisplayIdentification.cpp
index 5cdaa71627..8d6f74b605 100644
--- a/libs/ui/DisplayIdentification.cpp
+++ b/libs/ui/DisplayIdentification.cpp
@@ -249,7 +249,8 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
     view = view.subspan(kDescriptorOffset);
 
     std::string_view displayName;
-    std::string_view serialNumber;
+    std::string_view descriptorBlockSerialNumber;
+    std::optional<uint64_t> hashedDescriptorBlockSNOpt = std::nullopt;
     std::string_view asciiText;
     ui::Size preferredDTDPixelSize;
     ui::Size preferredDTDPhysicalSize;
@@ -274,7 +275,10 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
                     asciiText = parseEdidText(descriptor);
                     break;
                 case 0xff:
-                    serialNumber = parseEdidText(descriptor);
+                    descriptorBlockSerialNumber = parseEdidText(descriptor);
+                    hashedDescriptorBlockSNOpt = descriptorBlockSerialNumber.empty()
+                            ? std::nullopt
+                            : ftl::stable_hash(descriptorBlockSerialNumber);
                     break;
             }
         } else if (isDetailedTimingDescriptor(view)) {
@@ -315,7 +319,7 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
 
     if (modelString.empty()) {
         ALOGW("Invalid EDID: falling back to serial number due to missing display name.");
-        modelString = serialNumber;
+        modelString = descriptorBlockSerialNumber;
     }
     if (modelString.empty()) {
         ALOGW("Invalid EDID: falling back to ASCII text due to missing serial number.");
@@ -369,6 +373,7 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
             .manufacturerId = manufacturerId,
             .productId = productId,
             .hashedBlockZeroSerialNumberOpt = hashedBlockZeroSNOpt,
+            .hashedDescriptorBlockSerialNumberOpt = hashedDescriptorBlockSNOpt,
             .pnpId = *pnpId,
             .modelHash = modelHash,
             .displayName = displayName,
-- 
cgit v1.2.3-59-g8ed1b