ozone: Allocate scanout buffer according to KMS modifiers

ui/ozone/platform/drm/gpu/drm_thread.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/platform/drm/gpu/drm_thread.h"
 
 #include <gbm.h>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 106 matching lines @@
       break;
     case gfx::BufferUsage::SCANOUT:
       flags = GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING;
       break;
     case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE:
     case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT:
       flags = GBM_BO_USE_LINEAR;
       break;
   }
 
-  *buffer = GbmBuffer::CreateBuffer(
-      gbm, ui::GetFourCCFormatFromBufferFormat(format), size, flags);
+  DCHECK(screen_manager_);

[dnicoara, 2016/12/19 19:44:46]

nit: No need to DCHECK, the following access will just crash if screen_manager_
is nullptr. Also, the only reason this would be nullptr is if Init() wasn't run.

[hoegsberg1, 2016/12/22 23:05:20]

Acknowledged.

+  DrmWindow* window = screen_manager_->GetWindow(widget);
+  std::vector<uint64_t> modifiers;
+
+  uint32_t fourcc_format = ui::GetFourCCFormatFromBufferFormat(format);
+
+  if (window && window->GetController())

[Daniele Castagna, 2016/12/20 18:03:28]

It'd be nice to understand why this happens, or at least leave a comment
mentioning we need to investigate further.
I don't think it's related to the logout button race we observed, since that one
was about adding ui elements.

[hoegsberg1, 2016/12/22 23:05:20]

I added a todo there.

+    modifiers = window->GetController()->GetFormatModifiers(fourcc_format);
+
+  if (modifiers.size() > 0 && !(flags & GBM_BO_USE_LINEAR)) {
+    *buffer = GbmBuffer::CreateBufferWithModifiers(gbm, fourcc_format, size,
+                                                   flags, modifiers);
+  } else {
+    *buffer = GbmBuffer::CreateBuffer(gbm, fourcc_format, size, flags);
+  }
 }
 
 void DrmThread::CreateBufferFromFds(
     gfx::AcceleratedWidget widget,
     const gfx::Size& size,
     gfx::BufferFormat format,
     std::vector<base::ScopedFD>&& fds,
     const std::vector<gfx::NativePixmapPlane>& planes,
     scoped_refptr<GbmBuffer>* buffer) {
   scoped_refptr<GbmDevice> gbm =
@@ skipping 134 matching lines @@
                                        correction_matrix);
 }
 
 // DrmThread requires a BindingSet instead of a simple Binding because it will
 // be used from multiple threads in multiple processes.
 void DrmThread::AddBinding(ozone::mojom::DeviceCursorRequest request) {
   bindings_.AddBinding(this, std::move(request));
 }
 
 }  // namespace ui