ozone: ClientPixmapManager passes VGEM fd from browser to renderer.

ui/ozone/platform/drm/common/client_native_pixmap_factory_gbm.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/common/client_native_pixmap_factory_gbm.h"
 
-#include "base/file_descriptor_posix.h"
 #include "ui/gfx/native_pixmap_handle_ozone.h"
 #include "ui/ozone/public/client_native_pixmap_factory.h"
 
 #if defined(USE_VGEM_MAP)
-#include <fcntl.h>
+#include "base/synchronization/waitable_event.h"
+#include "base/threading/platform_thread.h"
+#include "base/threading/thread_restrictions.h"
 #include "ui/ozone/platform/drm/gpu/client_native_pixmap_vgem.h"
 #endif
 
 namespace ui {
 
 namespace {
 
 class ClientNativePixmapGbm : public ClientNativePixmap {
  public:
   ClientNativePixmapGbm() {}
   ~ClientNativePixmapGbm() override {}
 
   void* Map() override {
     NOTREACHED();
     return nullptr;
   }
   void Unmap() override { NOTREACHED(); }
   void GetStride(int* stride) const override { NOTREACHED(); }
 };
 
+}  // namespace
+
 class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
  public:
-  ClientNativePixmapFactoryGbm() {
-#if defined(USE_VGEM_MAP)
-    // TODO(dshwang): remove ad-hoc file open. crrev.com/1248713002
-    static const char kVgemPath[] = "/dev/dri/renderD129";
-    int vgem_fd = open(kVgemPath, O_RDWR | O_CLOEXEC);
-    vgem_fd_.reset(vgem_fd);
-    DCHECK_GE(vgem_fd_.get(), 0) << "Failed to open: " << kVgemPath;
-#endif
-  }
+  ClientNativePixmapFactoryGbm() : set_vgem_fd_event_(true, false) {}
   ~ClientNativePixmapFactoryGbm() override {}
 
   // ClientNativePixmapFactory:
+  void Initialize(base::ScopedFD device_fd) override {
+#if defined(USE_VGEM_MAP)
+    DCHECK_LT(vgem_fd_.get(), 0);
+    vgem_fd_ = device_fd.Pass();
+#if DCHECK_IS_ON()
+    set_vgem_fd_thread_id_ = base::PlatformThread::CurrentRef();
+#endif
+    set_vgem_fd_event_.Signal();
+#endif
+  }
   std::vector<Configuration> GetSupportedConfigurations() const override {
     const Configuration kConfigurations[] = {
         {gfx::BufferFormat::BGRA_8888, gfx::BufferUsage::SCANOUT},
         {gfx::BufferFormat::BGRX_8888, gfx::BufferUsage::SCANOUT}};
     std::vector<Configuration> configurations(
         kConfigurations, kConfigurations + arraysize(kConfigurations));
 #if defined(USE_VGEM_MAP)
     configurations.push_back(
         {gfx::BufferFormat::BGRA_8888, gfx::BufferUsage::MAP});
 #endif
     return configurations;
   }
   scoped_ptr<ClientNativePixmap> ImportFromHandle(
       const gfx::NativePixmapHandle& handle,
       const gfx::Size& size,
       gfx::BufferUsage usage) override {
     base::ScopedFD scoped_fd(handle.fd.fd);
 
     switch (usage) {
       case gfx::BufferUsage::MAP:
 #if defined(USE_VGEM_MAP)
+        // A valid |vgem_fd_| is required to acquire a VGEM bo. This will wait
+        // for a valid |vgem_fd_| if one has not yet been set.
+        {
+          base::ThreadRestrictions::ScopedAllowWait allow_wait;
+          set_vgem_fd_event_.Wait();
+        }
+#if DCHECK_IS_ON()
+        DCHECK(!(set_vgem_fd_thread_id_ == base::PlatformThread::CurrentRef()));
+#endif
+        DCHECK_GE(vgem_fd_.get(), 0);

[reveman, 2015/08/25 17:06:19]

I think this DCHECK_GE is all we need after discussing this with jam@. As the
InitializeClientNativePixmapFactory message is being handled on the IO thread,
there's no way this could be called without that first being processed. It would
require that we tried to allocate a buffer before a widget is created and that
should not happen today and can be considered unsupported.

I think the need in the IOSurfaceManager case is from a time when this message
was not handled on the IO thread. I'll change the IOSurfaceManager code to use a
DCHECK too instead of a Wait in a separate CL.

[dshwang, 2015/08/26 13:27:44]

That's excellent conclusion which everybody is happy. Thank you for your
investigation. I updated.

         return ClientNativePixmapVgem::ImportFromDmabuf(
             vgem_fd_.get(), scoped_fd.get(), size, handle.stride);
 #endif
         NOTREACHED();
         return nullptr;
       case gfx::BufferUsage::PERSISTENT_MAP:
         NOTREACHED();
         return nullptr;
       case gfx::BufferUsage::SCANOUT:
         return make_scoped_ptr<ClientNativePixmapGbm>(
             new ClientNativePixmapGbm);
     }
     NOTREACHED();
     return nullptr;
   }
 
  private:
 #if defined(USE_VGEM_MAP)
   base::ScopedFD vgem_fd_;
+#if DCHECK_IS_ON()
+  base::PlatformThreadRef set_vgem_fd_thread_id_;
+#endif
+  base::WaitableEvent set_vgem_fd_event_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ClientNativePixmapFactoryGbm);
 };
 
-}  // namespace
-
 ClientNativePixmapFactory* CreateClientNativePixmapFactoryGbm() {
   return new ClientNativePixmapFactoryGbm();
 }
 
 }  // namespace ui