commit f0c507f16b99ff9ac30fb1a95fd1d1c1c9eaf55a
author Roman Stratiienko <roman.o.stratiienko@globallogic.com> Mon Jan 17 18:29:24 2022 +0200
committer Roman Stratiienko <roman.o.stratiienko@globallogic.com> Thu Jan 20 17:21:46 2022 +0200
tree 01819d17b3a3b427f84d648054d1ea50c3ce1d77
parent aa8ec5204dc019acab6b20b1830469c414439ee7

drm_hwcomposer: Add headless mode support

Headless mode required to keep SurfaceFlinger alive when all displays are
disconnected, Without headless mode Android will continuously crash.
Only single internal (primary) display is required to be in HEADLESS mode
to prevent the crash. See [1].

[1]: https://source.android.com/devices/graphics/hotplug#handling-common-scenarios
Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/57
Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>

hwc2_device/HwcDisplay.cpp

diff --git a/hwc2_device/HwcDisplay.cpp b/hwc2_device/HwcDisplay.cpp
index 0ceafed..8936136 100644
--- a/hwc2_device/HwcDisplay.cpp
+++ b/hwc2_device/HwcDisplay.cpp
@@ -98,6 +98,11 @@
 }
 
 void HwcDisplay::ClearDisplay() {
+  if (IsInHeadlessMode()) {
+    ALOGE("%s: Headless mode, should never reach here: ", __func__);
+    return;
+  }
+
   AtomicCommitArgs a_args = {.clear_active_composition = true};
   compositor_.ExecuteAtomicCommit(a_args);
 }
@@ -192,7 +197,7 @@
 
 HWC2::Error HwcDisplay::ChosePreferredConfig() {
   HWC2::Error err = configs_.Update(*connector_);
-  if (err != HWC2::Error::None)
+  if (!IsInHeadlessMode() && err != HWC2::Error::None)
     return HWC2::Error::BadDisplay;
 
   return SetActiveConfig(configs_.preferred_config_id);
@@ -230,6 +235,11 @@
 HWC2::Error HwcDisplay::GetChangedCompositionTypes(uint32_t *num_elements,
                                                    hwc2_layer_t *layers,
                                                    int32_t *types) {
+  if (IsInHeadlessMode()) {
+    *num_elements = 0;
+    return HWC2::Error::None;
+  }
+
   uint32_t num_changes = 0;
   for (std::pair<const hwc2_layer_t, HwcLayer> &l : layers_) {
     if (l.second.IsTypeChanged()) {
@@ -250,6 +260,9 @@
                                                int32_t dataspace) {
   std::pair<uint32_t, uint32_t> min = drm_->min_resolution();
   std::pair<uint32_t, uint32_t> max = drm_->max_resolution();
+  if (IsInHeadlessMode()) {
+    return HWC2::Error::None;
+  }
 
   if (width < min.first || height < min.second)
     return HWC2::Error::Unsupported;
@@ -287,8 +300,8 @@
   auto &hwc_config = configs_.hwc_configs[conf];
 
   static const int32_t kUmPerInch = 25400;
-  uint32_t mm_width = connector_->mm_width();
-  uint32_t mm_height = connector_->mm_height();
+  uint32_t mm_width = configs_.mm_width;
+  uint32_t mm_height = configs_.mm_height;
   auto attribute = static_cast<HWC2::Attribute>(attribute_in);
   switch (attribute) {
     case HWC2::Attribute::Width:
@@ -398,6 +411,11 @@
 HWC2::Error HwcDisplay::GetReleaseFences(uint32_t *num_elements,
                                          hwc2_layer_t *layers,
                                          int32_t *fences) {
+  if (IsInHeadlessMode()) {
+    *num_elements = 0;
+    return HWC2::Error::None;
+  }
+
   uint32_t num_layers = 0;
 
   for (std::pair<const hwc2_layer_t, HwcLayer> &l : layers_) {
@@ -418,6 +436,11 @@
 }
 
 HWC2::Error HwcDisplay::CreateComposition(AtomicCommitArgs &a_args) {
+  if (IsInHeadlessMode()) {
+    ALOGE("%s: Display is in headless mode, should never reach here", __func__);
+    return HWC2::Error::None;
+  }
+
   // order the layers by z-order
   bool use_client_layer = false;
   uint32_t client_z_order = UINT32_MAX;
@@ -497,6 +520,10 @@
  * https://cs.android.com/android/platform/superproject/+/android-11.0.0_r3:hardware/libhardware/include/hardware/hwcomposer2.h;l=1805
  */
 HWC2::Error HwcDisplay::PresentDisplay(int32_t *present_fence) {
+  if (IsInHeadlessMode()) {
+    *present_fence = -1;
+    return HWC2::Error::None;
+  }
   HWC2::Error ret{};
 
   ++total_stats_.total_frames_;
@@ -611,6 +638,10 @@
 }
 
 HWC2::Error HwcDisplay::SetPowerMode(int32_t mode_in) {
+  if (IsInHeadlessMode()) {
+    return HWC2::Error::None;
+  }
+
   auto mode = static_cast<HWC2::PowerMode>(mode_in);
   AtomicCommitArgs a_args{};
 
@@ -652,6 +683,10 @@
 
 HWC2::Error HwcDisplay::ValidateDisplay(uint32_t *num_types,
                                         uint32_t *num_requests) {
+  if (IsInHeadlessMode()) {
+    *num_types = *num_requests = 0;
+    return HWC2::Error::None;
+  }
   return backend_->ValidateDisplay(this, num_types, num_requests);
 }