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/HwcDisplayConfigs.cpp

diff --git a/hwc2_device/HwcDisplayConfigs.cpp b/hwc2_device/HwcDisplayConfigs.cpp
index e3d17a2..16f1ed0 100644
--- a/hwc2_device/HwcDisplayConfigs.cpp
+++ b/hwc2_device/HwcDisplayConfigs.cpp
@@ -23,10 +23,38 @@
 #include "drm/DrmConnector.h"
 #include "utils/log.h"
 
+constexpr uint32_t kHeadlessModeDisplayWidthMm = 163;
+constexpr uint32_t kHeadlessModeDisplayHeightMm = 122;
+constexpr uint32_t kHeadlessModeDisplayWidthPx = 1024;
+constexpr uint32_t kHeadlessModeDisplayHeightPx = 768;
+constexpr uint32_t kHeadlessModeDisplayVRefresh = 60;
+
 namespace android {
 
 // NOLINTNEXTLINE (readability-function-cognitive-complexity): Fixme
 HWC2::Error HwcDisplayConfigs::Update(DrmConnector &connector) {
+  /* In case UpdateModes will fail we will still have one mode for headless
+   * mode*/
+  hwc_configs.clear();
+
+  last_config_id++;
+  preferred_config_id = active_config_id = last_config_id;
+  auto headless_drm_mode_info = (drmModeModeInfo){
+      .hdisplay = kHeadlessModeDisplayWidthPx,
+      .vdisplay = kHeadlessModeDisplayHeightPx,
+      .vrefresh = kHeadlessModeDisplayVRefresh,
+      .name = "HEADLESS-MODE",
+  };
+  hwc_configs[active_config_id] = (HwcDisplayConfig){
+      .id = active_config_id,
+      .group_id = 1,
+      .mode = DrmMode(&headless_drm_mode_info),
+  };
+
+  mm_width = kHeadlessModeDisplayWidthMm;
+  mm_height = kHeadlessModeDisplayHeightMm;
+
+  /* Read real configs */
   int ret = connector.UpdateModes();
   if (ret != 0) {
     ALOGE("Failed to update display modes %d", ret);
@@ -39,6 +67,9 @@
   }
 
   hwc_configs.clear();
+  mm_width = connector.mm_width();
+  mm_height = connector.mm_height();
+
   preferred_config_id = 0;
   int preferred_config_group_id = 0;
 
@@ -159,6 +190,8 @@
     }
   }
 
+  /* Set active mode to be valid mode */
+  active_config_id = preferred_config_id;
   return HWC2::Error::None;
 }