commit e9ef7c430a223bfebe0d5206f72b1b20af0a0d23
author Dominik Laskowski <domlaskowski@google.com> Mon Mar 12 19:34:30 2018 -0700
committer Dominik Laskowski <domlaskowski@google.com> Mon Apr 30 10:44:35 2018 -0700
tree ab849f69e7f22d259c21007bc842618d5803d924
parent 555c303adccae00d428cd6b6187680b36f0ef262

SF: Generate stable display IDs using EDID

The display IDs generated by HWC are opaque handles. In order for SF and
eventually DisplayManagerService to keep track of more than two displays
and recognize previously seen displays, displays should be given stable
and persistent IDs.

If the HWC supports IComposerClient.getDisplayIdentificationData, SF
parses the EDID structure to generate stable display IDs, which will
be used in a follow-up CL to replace HWC_DISPLAY_{PRIMARY,EXTERNAL}.

Bug: 74619554
Test: dumpsys SurfaceFlinger --display-identification
Test: libsurfaceflinger_unittest
Change-Id: I1a710e2efcf1581fabe48ab96a0eb4e7a5163c0c

services/surfaceflinger/DisplayHardware/HWComposer.cpp

diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index f111f2b..8e54392 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -96,6 +96,22 @@
     mHwcDevice->registerCallback(callback, sequenceId);
 }
 
+bool HWComposer::getDisplayIdentificationData(hwc2_display_t displayId, uint8_t* outPort,
+                                              DisplayIdentificationData* outData) const {
+    HWC2::Display* display = mHwcDevice->getDisplayById(displayId);
+    if (!display) {
+        ALOGE("getDisplayIdentificationData: Attempted to access invalid display %" PRIu64,
+              displayId);
+        return false;
+    }
+    const auto error = display->getIdentificationData(outPort, outData);
+    if (error != HWC2::Error::None) {
+        ALOGE("getDisplayIdentificationData failed for display %" PRIu64, displayId);
+        return false;
+    }
+    return true;
+}
+
 bool HWComposer::hasCapability(HWC2::Capability capability) const
 {
     return mHwcDevice->getCapabilities().count(capability) > 0;
@@ -131,23 +147,35 @@
     }
 }
 
-void HWComposer::onHotplug(hwc2_display_t displayId, int32_t displayType,
-                           HWC2::Connection connection) {
+std::optional<DisplayId> HWComposer::onHotplug(hwc2_display_t displayId, int32_t displayType,
+                                               HWC2::Connection connection) {
     if (displayType >= HWC_NUM_PHYSICAL_DISPLAY_TYPES) {
         ALOGE("Invalid display type of %d", displayType);
-        return;
+        return {};
     }
 
     ALOGV("hotplug: %" PRIu64 ", %s %s", displayId,
             displayType == DisplayDevice::DISPLAY_PRIMARY ? "primary" : "external",
             to_string(connection).c_str());
     mHwcDevice->onHotplug(displayId, connection);
+
+    std::optional<DisplayId> stableId;
+
+    uint8_t port;
+    DisplayIdentificationData data;
+    if (getDisplayIdentificationData(displayId, &port, &data)) {
+        stableId = generateDisplayId(port, data);
+        ALOGE_IF(!stableId, "Failed to generate stable ID for display %" PRIu64, displayId);
+    }
+
     // Disconnect is handled through HWComposer::disconnectDisplay via
     // SurfaceFlinger's onHotplugReceived callback handling
     if (connection == HWC2::Connection::Connected) {
         mDisplayData[displayType].hwcDisplay = mHwcDevice->getDisplayById(displayId);
         mHwcDisplaySlots[displayId] = displayType;
     }
+
+    return stableId;
 }
 
 bool HWComposer::onVsync(hwc2_display_t displayId, int64_t timestamp,