From 8d0a0c43c1416e8540b0adf527be2ec5c69cccff Mon Sep 17 00:00:00 2001
From: Lucas Berthou <berlu@google.com>
Date: Tue, 27 Aug 2024 14:32:31 +0000
Subject: SF: parsing Detailed Timing Descriptor in the framework

The first DTD in an edid is the preferred timing which allows to get
a more precise and more often correct physical size for a display. This
can be used to estimate or correct the dpi in case the edid reports the
wrong size and hwc is not providing the right value.

See edid spec: https://glenwing.github.io/docs/VESA-EEDID-A2.pdf

Flag: com.android.graphics.surfaceflinger.flags.correct_dpi_with_display_size
Bug: 361413340
Test: DisplayIdentification_test
Test: HWComposerTest
Test: manual - see bug and doc

Change-Id: I0bb85dcf8039f923f1ac892c4a1d6bda771dbf4f
---
 libs/ui/DisplayIdentification.cpp | 69 ++++++++++++++++++++++++++++++++-------
 1 file changed, 58 insertions(+), 11 deletions(-)

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

diff --git a/libs/ui/DisplayIdentification.cpp b/libs/ui/DisplayIdentification.cpp
index e5af7406ed..8b13d78840 100644
--- a/libs/ui/DisplayIdentification.cpp
+++ b/libs/ui/DisplayIdentification.cpp
@@ -26,6 +26,7 @@
 #include <ftl/hash.h>
 #include <log/log.h>
 #include <ui/DisplayIdentification.h>
+#include <ui/Size.h>
 
 namespace android {
 namespace {
@@ -46,6 +47,10 @@ std::optional<uint8_t> getEdidDescriptorType(const byte_view& view) {
     return view[3];
 }
 
+bool isDetailedTimingDescriptor(const byte_view& view) {
+    return view[0] != 0 && view[1] != 0;
+}
+
 std::string_view parseEdidText(const byte_view& view) {
     std::string_view text(reinterpret_cast<const char*>(view.data()), view.size());
     text = text.substr(0, text.find('\n'));
@@ -219,6 +224,8 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
     std::string_view displayName;
     std::string_view serialNumber;
     std::string_view asciiText;
+    ui::Size preferredDTDPixelSize;
+    ui::Size preferredDTDPhysicalSize;
 
     constexpr size_t kDescriptorCount = 4;
     constexpr size_t kDescriptorLength = 18;
@@ -243,6 +250,35 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
                     serialNumber = parseEdidText(descriptor);
                     break;
             }
+        } else if (isDetailedTimingDescriptor(view)) {
+            static constexpr size_t kHorizontalPhysicalLsbOffset = 12;
+            static constexpr size_t kHorizontalPhysicalMsbOffset = 14;
+            static constexpr size_t kVerticalPhysicalLsbOffset = 13;
+            static constexpr size_t kVerticalPhysicalMsbOffset = 14;
+            const uint32_t hSize =
+                    static_cast<uint32_t>(view[kHorizontalPhysicalLsbOffset] |
+                                          ((view[kHorizontalPhysicalMsbOffset] >> 4) << 8));
+            const uint32_t vSize =
+                    static_cast<uint32_t>(view[kVerticalPhysicalLsbOffset] |
+                                          ((view[kVerticalPhysicalMsbOffset] & 0b1111) << 8));
+
+            static constexpr size_t kHorizontalPixelLsbOffset = 2;
+            static constexpr size_t kHorizontalPixelMsbOffset = 4;
+            static constexpr size_t kVerticalPixelLsbOffset = 5;
+            static constexpr size_t kVerticalPixelMsbOffset = 7;
+
+            const uint8_t hLsb = view[kHorizontalPixelLsbOffset];
+            const uint8_t hMsb = view[kHorizontalPixelMsbOffset];
+            const int32_t hPixel = hLsb + ((hMsb & 0xF0) << 4);
+
+            const uint8_t vLsb = view[kVerticalPixelLsbOffset];
+            const uint8_t vMsb = view[kVerticalPixelMsbOffset];
+            const int32_t vPixel = vLsb + ((vMsb & 0xF0) << 4);
+
+            preferredDTDPixelSize.setWidth(hPixel);
+            preferredDTDPixelSize.setHeight(vPixel);
+            preferredDTDPhysicalSize.setWidth(hSize);
+            preferredDTDPhysicalSize.setHeight(vSize);
         }
 
         view = view.subspan(kDescriptorLength);
@@ -297,14 +333,22 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
         }
     }
 
-    return Edid{.manufacturerId = manufacturerId,
-                .productId = productId,
-                .pnpId = *pnpId,
-                .modelHash = modelHash,
-                .displayName = displayName,
-                .manufactureOrModelYear = manufactureOrModelYear,
-                .manufactureWeek = manufactureWeek,
-                .cea861Block = cea861Block};
+    DetailedTimingDescriptor preferredDetailedTimingDescriptor{
+            .pixelSizeCount = preferredDTDPixelSize,
+            .physicalSizeInMm = preferredDTDPhysicalSize,
+    };
+
+    return Edid{
+            .manufacturerId = manufacturerId,
+            .productId = productId,
+            .pnpId = *pnpId,
+            .modelHash = modelHash,
+            .displayName = displayName,
+            .manufactureOrModelYear = manufactureOrModelYear,
+            .manufactureWeek = manufactureWeek,
+            .cea861Block = cea861Block,
+            .preferredDetailedTimingDescriptor = preferredDetailedTimingDescriptor,
+    };
 }
 
 std::optional<PnpId> getPnpId(uint16_t manufacturerId) {
@@ -336,9 +380,12 @@ std::optional<DisplayIdentificationInfo> parseDisplayIdentificationData(
     }
 
     const auto displayId = PhysicalDisplayId::fromEdid(port, edid->manufacturerId, edid->modelHash);
-    return DisplayIdentificationInfo{.id = displayId,
-                                     .name = std::string(edid->displayName),
-                                     .deviceProductInfo = buildDeviceProductInfo(*edid)};
+    return DisplayIdentificationInfo{
+            .id = displayId,
+            .name = std::string(edid->displayName),
+            .deviceProductInfo = buildDeviceProductInfo(*edid),
+            .preferredDetailedTimingDescriptor = edid->preferredDetailedTimingDescriptor,
+    };
 }
 
 PhysicalDisplayId getVirtualDisplayId(uint32_t id) {
-- 
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