commit f2c060f8be1ed1270728b43a2588d3b9eb00c292
author Roman Stratiienko <r.stratiienko@gmail.com> Mon Sep 18 22:46:08 2023 +0300
committer Roman Stratiienko <r.stratiienko@gmail.com> Sun Oct 01 15:00:59 2023 +0300
tree fa79d38263dbfa983067bc2bded41265ea98ac6a
parent 63762a9d5d131bb20b29d9ab92c2ddbd7dc1889e

drm_hwcomposer: Virtual display acceleration support

Some platforms like RaspberryPI-4 can benefit from Display Blender IP Core's
ability to write back the composition into RAM, offloading the GPU in cases
where the display content needs to be used (screen record, remote display,
etc.).

To enable this feature the following system property must be enabled:

    PRODUCT_VENDOR_PROPERTIES += debug.sf.enable_hwc_vds=1

The feature was requested by the Tesla Android project to improve UI
performance.

Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/4
Change-Id: I643f94551408bf218a0b889f1a031598646242f1
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>

hwc2_device/DrmHwcTwo.cpp

diff --git a/hwc2_device/DrmHwcTwo.cpp b/hwc2_device/DrmHwcTwo.cpp
index 99756eb..b151155 100644
--- a/hwc2_device/DrmHwcTwo.cpp
+++ b/hwc2_device/DrmHwcTwo.cpp
@@ -124,17 +124,47 @@
   return true;
 }
 
-HWC2::Error DrmHwcTwo::CreateVirtualDisplay(uint32_t /*width*/,
-                                            uint32_t /*height*/,
-                                            int32_t * /*format*/,
-                                            hwc2_display_t * /*display*/) {
-  // TODO(nobody): Implement virtual display
-  return HWC2::Error::Unsupported;
+HWC2::Error DrmHwcTwo::CreateVirtualDisplay(
+    uint32_t width, uint32_t height,
+    int32_t *format,  // NOLINT(readability-non-const-parameter)
+    hwc2_display_t *display) {
+  ALOGI("Creating virtual display %dx%d format %d", width, height, *format);
+
+  auto virtual_pipeline = resource_manager_.GetVirtualDisplayPipeline();
+  if (!virtual_pipeline)
+    return HWC2::Error::Unsupported;
+
+  *display = ++last_display_handle_;
+  auto disp = std::make_unique<HwcDisplay>(*display, HWC2::DisplayType::Virtual,
+                                           this);
+
+  disp->SetVirtualDisplayResolution(width, height);
+  disp->SetPipeline(virtual_pipeline);
+  displays_[*display] = std::move(disp);
+  return HWC2::Error::None;
 }
 
-HWC2::Error DrmHwcTwo::DestroyVirtualDisplay(hwc2_display_t /*display*/) {
-  // TODO(nobody): Implement virtual display
-  return HWC2::Error::Unsupported;
+HWC2::Error DrmHwcTwo::DestroyVirtualDisplay(hwc2_display_t display) {
+  ALOGI("Destroying virtual display %" PRIu64, display);
+
+  if (displays_.count(display) == 0) {
+    ALOGE("Trying to destroy non-existent display %" PRIu64, display);
+    return HWC2::Error::BadDisplay;
+  }
+
+  displays_[display]->SetPipeline({});
+
+  /* Wait 0.2s before removing the displays to flush pending HWC2 transactions
+   */
+  auto &mutex = GetResMan().GetMainLock();
+  mutex.unlock();
+  const int kTimeForSFToDisposeDisplayUs = 200000;
+  usleep(kTimeForSFToDisposeDisplayUs);
+  mutex.lock();
+
+  displays_.erase(display);
+
+  return HWC2::Error::None;
 }
 
 void DrmHwcTwo::Dump(uint32_t *outSize, char *outBuffer) {
@@ -156,8 +186,11 @@
 }
 
 uint32_t DrmHwcTwo::GetMaxVirtualDisplayCount() {
-  // TODO(nobody): Implement virtual display
-  return 0;
+  auto writeback_count = resource_manager_.GetWritebackConnectorsCount();
+  writeback_count = std::min(writeback_count, 1U);
+  /* Currently, only 1 virtual display is supported. Other cases need testing */
+  ALOGI("Max virtual display count: %d", writeback_count);
+  return writeback_count;
 }
 
 HWC2::Error DrmHwcTwo::RegisterCallback(int32_t descriptor,