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If you follow the code @line 160: // First look for primary amongst internal connectors

  // First look for primary amongst internal connectors
  for (auto &conn : connectors_) {
    if (conn->internal() && !found_primary) {
      conn->set_display(0);
      found_primary = true;
    } else {
      conn->set_display(display_num);
      ++display_num;
    }
  }

  // Then look for primary amongst external connectors
  for (auto &conn : connectors_) {
    if (conn->external() && !found_primary) {
      conn->set_display(0);
      found_primary = true;
    }
  }

if any internal connector is present display 0 is set and considered as primary. With discrete GPUs, having multiple connectors, that is not correct.

Hack [1] even if a ugly hack and does not consider multiple displays, avoids the current defect in assigning display 0 and found_primary, because by changing the current logic the Android GUI can boot with nouveau,

with the current implementation Android cannot boot on any discrete GPU.

This ticket purpose is to have a placeholder to correct the defect in some way.

Mauro Rossi

[1] https://github.com/maurossi/drm_hwcomposer/commit/a3fc27612d98bba1a3f3d959d557af2d49ad5889