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/HwcDisplayConfigs.cpp

diff --git a/hwc2_device/HwcDisplayConfigs.cpp b/hwc2_device/HwcDisplayConfigs.cpp
index 9727989..f6bf4a1 100644
--- a/hwc2_device/HwcDisplayConfigs.cpp
+++ b/hwc2_device/HwcDisplayConfigs.cpp
@@ -19,6 +19,7 @@
 #include "HwcDisplayConfigs.h"
 
 #include <cmath>
+#include <cstring>
 
 #include "drm/DrmConnector.h"
 #include "utils/log.h"
@@ -28,23 +29,53 @@
 constexpr uint32_t kHeadlessModeDisplayWidthPx = 1024;
 constexpr uint32_t kHeadlessModeDisplayHeightPx = 768;
 constexpr uint32_t kHeadlessModeDisplayVRefresh = 60;
+constexpr uint32_t kSyncLen = 10;
+constexpr uint32_t kBackPorch = 10;
+constexpr uint32_t kFrontPorch = 10;
+constexpr uint32_t kHzInKHz = 1000;
 
 namespace android {
 
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
 uint32_t HwcDisplayConfigs::last_config_id = 1;
 
-void HwcDisplayConfigs::FillHeadless() {
+void HwcDisplayConfigs::GenFakeMode(uint16_t width, uint16_t height) {
   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,
+      .hdisplay = width,
+      .vdisplay = height,
       .vrefresh = kHeadlessModeDisplayVRefresh,
-      .name = "HEADLESS-MODE",
+      .name = "VIRTUAL-MODE",
   };
+
+  if (width == 0 || height == 0) {
+    strcpy(headless_drm_mode_info.name, "HEADLESS-MODE");
+    headless_drm_mode_info.hdisplay = kHeadlessModeDisplayWidthPx;
+    headless_drm_mode_info.vdisplay = kHeadlessModeDisplayHeightPx;
+  }
+
+  /* We need a valid mode to pass the kernel validation */
+
+  headless_drm_mode_info.hsync_start = headless_drm_mode_info.hdisplay +
+                                       kFrontPorch;
+  headless_drm_mode_info.hsync_end = headless_drm_mode_info.hsync_start +
+                                     kSyncLen;
+  headless_drm_mode_info.htotal = headless_drm_mode_info.hsync_end + kBackPorch;
+
+  headless_drm_mode_info.vsync_start = headless_drm_mode_info.vdisplay +
+                                       kFrontPorch;
+  headless_drm_mode_info.vsync_end = headless_drm_mode_info.vsync_start +
+                                     kSyncLen;
+  headless_drm_mode_info.vtotal = headless_drm_mode_info.vsync_end + kBackPorch;
+
+  headless_drm_mode_info.clock = (headless_drm_mode_info.htotal *
+                                  headless_drm_mode_info.vtotal *
+                                  headless_drm_mode_info.vrefresh) /
+                                 kHzInKHz;
+
   hwc_configs[active_config_id] = (HwcDisplayConfig){
       .id = active_config_id,
       .group_id = 1,
@@ -58,8 +89,9 @@
 // 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*/
-  FillHeadless();
+   * mode
+   */
+  GenFakeMode(0, 0);
   /* Read real configs */
   auto ret = connector.UpdateModes();
   if (ret != 0) {