drm_hwcomposer: Remove legacy GetDisplayName

Remove the HWC2 GetDisplayName hook from HwcDisplay and replace it with
a function that simply returns the std::string.

Implement the HWC2 and HWC3 frontends in terms of the new
HwcDisplay::GetDisplayName.

Change-Id: I8230294bb7195b6d011ea450fafb80db8c9c5f50
Signed-off-by: Drew Davenport <ddavenport@google.com>

hwc2_device/HwcDisplay.cpp

@@ -145,6 +145,16 @@ std::string HwcDisplay::Dump() {
   return ss.str();
 }
 
+auto HwcDisplay::GetDisplayName() -> std::string {
+  std::ostringstream stream;
+  if (IsInHeadlessMode()) {
+    stream << "null-display";
+  } else {
+    stream << "display-" << GetPipe().connector->Get()->GetId();
+  }
+  return stream.str();
+}
+
 HwcDisplay::HwcDisplay(hwc2_display_t handle, bool is_virtual, DrmHwc *hwc)
     : hwc_(hwc), handle_(handle), is_virtual_(is_virtual), client_layer_(this) {
   // Create writeback layer for both virtual displays and potential readback
@@ -667,25 +677,6 @@ HWC2::Error HwcDisplay::GetColorModes(uint32_t *num_modes, int32_t *modes) {
   return HWC2::Error::None;
 }
 
-HWC2::Error HwcDisplay::GetDisplayName(uint32_t *size, char *name) {
-  std::ostringstream stream;
-  if (IsInHeadlessMode()) {
-    stream << "null-display";
-  } else {
-    stream << "display-" << GetPipe().connector->Get()->GetId();
-  }
-  auto string = stream.str();
-  auto length = string.length();
-  if (!name) {
-    *size = length;
-    return HWC2::Error::None;
-  }
-
-  *size = std::min<uint32_t>(static_cast<uint32_t>(length - 1), *size);
-  strncpy(name, string.c_str(), *size);
-  return HWC2::Error::None;
-}
-
 HWC2::Error HwcDisplay::GetHdrCapabilities(uint32_t *num_types, int32_t *types,
                                            float *max_luminance,
                                            float *max_average_luminance,

hwc2_device/HwcDisplay.h

@@ -74,6 +74,8 @@ class HwcDisplay {
 
   std::string Dump();
 
+  auto GetDisplayName() -> std::string;
+
   const HwcDisplayConfigs &GetDisplayConfigs() const {
     return configs_;
   }
@@ -152,7 +154,6 @@ class HwcDisplay {
 
   // HWC2 Hooks - these should not be used outside of the hwc2 device.
   HWC2::Error GetColorModes(uint32_t *num_modes, int32_t *modes);
-  HWC2::Error GetDisplayName(uint32_t *size, char *name);
 #if __ANDROID_API__ > 27
   HWC2::Error GetRenderIntents(int32_t mode, uint32_t *outNumIntents,
                                int32_t *outIntents);

hwc2_device/hwc2_device.cpp

@@ -508,6 +508,24 @@ static int32_t GetDisplayConfigs(hwc2_device_t *device, hwc2_display_t display,
   return 0;
 }
 
+static int32_t GetDisplayName(hwc2_device_t *device, hwc2_display_t display,
+                              uint32_t *size, char *name) {
+  ALOGV("GetDisplayName");
+  LOCK_COMPOSER(device);
+  GET_DISPLAY(display);
+
+  std::string name_str = idisplay->GetDisplayName();
+
+  auto length = name_str.length();
+  if (name == nullptr) {
+    *size = length;
+    return 0;
+  }
+
+  *size = std::min<uint32_t>(static_cast<uint32_t>(length - 1), *size);
+  strncpy(name, name_str.c_str(), *size);
+  return 0;
+}
 static int32_t SetOutputBuffer(hwc2_device_t *device, hwc2_display_t display,
                                buffer_handle_t buffer, int32_t release_fence) {
   ALOGV("SetOutputBuffer");
@@ -1147,9 +1165,7 @@ static hwc2_function_pointer_t HookDevGetFunction(struct hwc2_device * /*dev*/,
     case HWC2::FunctionDescriptor::GetDisplayConfigs:
       return (hwc2_function_pointer_t)GetDisplayConfigs;
     case HWC2::FunctionDescriptor::GetDisplayName:
-      return ToHook<HWC2_PFN_GET_DISPLAY_NAME>(
-          DisplayHook<decltype(&HwcDisplay::GetDisplayName),
-                      &HwcDisplay::GetDisplayName, uint32_t *, char *>);
+      return (hwc2_function_pointer_t)GetDisplayName;
     case HWC2::FunctionDescriptor::GetDisplayRequests:
       return (hwc2_function_pointer_t)GetDisplayRequests;
     case HWC2::FunctionDescriptor::GetDisplayType:

hwc3/ComposerClient.cpp

@@ -1014,15 +1014,8 @@ ndk::ScopedAStatus ComposerClient::getDisplayName(int64_t display_id,
     return ToBinderStatus(hwc3::Error::kBadDisplay);
   }
 
-  uint32_t size = 0;
-  auto error = Hwc2toHwc3Error(display->GetDisplayName(&size, nullptr));
-  if (error != hwc3::Error::kNone) {
-    return ToBinderStatus(error);
-  }
-
-  name->resize(size);
-  error = Hwc2toHwc3Error(display->GetDisplayName(&size, name->data()));
-  return ToBinderStatus(error);
+  *name = display->GetDisplayName();
+  return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus ComposerClient::getDisplayVsyncPeriod(