drm: GPU process manages VGEM fd.

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

Index: ui/ozone/platform/drm/gpu/drm_device_manager.cc
diff --git a/ui/ozone/platform/drm/gpu/drm_device_manager.cc b/ui/ozone/platform/drm/gpu/drm_device_manager.cc
index b01664abb706586b1332aee3d22d82fa6f87a5f0..4f1dc0f8849929fd022b39c190fd567dd6223344 100644
--- a/ui/ozone/platform/drm/gpu/drm_device_manager.cc
+++ b/ui/ozone/platform/drm/gpu/drm_device_manager.cc
@@ -38,8 +38,16 @@ DrmDeviceManager::~DrmDeviceManager() {
 }
 
 bool DrmDeviceManager::AddDrmDevice(const base::FilePath& path,
-                                    const base::FileDescriptor& fd) {
+                                    const base::FileDescriptor& fd,
+                                    bool is_vgem) {
   DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (is_vgem) {
+    vgem_device_.reset(fd.fd);
+    vgem_path_ = path;
+    return true;
+  }
+
   base::File file(fd.fd);
   auto it =
       std::find_if(devices_.begin(), devices_.end(), FindByDevicePath(path));
@@ -67,6 +75,12 @@ bool DrmDeviceManager::AddDrmDevice(const base::FilePath& path,
 
 void DrmDeviceManager::RemoveDrmDevice(const base::FilePath& path) {
   DCHECK(thread_checker_.CalledOnValidThread());
+  if (vgem_path_ == path) {

[dnicoara, 2015/05/12 15:41:22]

Should it be possible to remove the VGEM device? If yes, maybe we shouldn't
cache the path of the VGEM device in DrmDisplayHostManager.

[dshwang, 2015/05/12 16:18:57]

What's mean? IMO it's impossible for chromium to drop vgem kernel module. vgem
path is immutable since chromebook booting.

+    vgem_device_.reset();
+    vgem_path_ = base::FilePath();
+    return;
+  }
+
   auto it =
       std::find_if(devices_.begin(), devices_.end(), FindByDevicePath(path));
   if (it == devices_.end()) {
@@ -123,4 +137,9 @@ const DrmDeviceVector& DrmDeviceManager::GetDrmDevices() const {
   return devices_;
 }
 
+int DrmDeviceManager::GetVgemDevice() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return vgem_device_.get();
+}
+
 }  // namespace ui