drm: GPU process manages VGEM fd.

ui/ozone/platform/drm/host/drm_display_host_manager.cc

 // Copyright 2014 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/host/drm_display_host_manager.h"
 
 #include <fcntl.h>
 #include <stdio.h>
 #include <xf86drm.h>
 
+#include "base/files/file_enumerator.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/worker_pool.h"
 #include "ui/display/types/display_snapshot.h"
 #include "ui/events/ozone/device/device_event.h"
 #include "ui/events/ozone/device/device_manager.h"
 #include "ui/ozone/common/display_snapshot_proxy.h"
 #include "ui/ozone/common/display_util.h"
 #include "ui/ozone/common/gpu/ozone_gpu_messages.h"
 #include "ui/ozone/platform/drm/host/drm_device_handle.h"
 #include "ui/ozone/platform/drm/host/drm_gpu_platform_support_host.h"
 #include "ui/ozone/platform/drm/host/drm_native_display_delegate.h"
 
 namespace ui {
 
 namespace {
 
 typedef base::Callback<void(const base::FilePath&, scoped_ptr<DrmDeviceHandle>)>
     OnOpenDeviceReplyCallback;
 
 const char kDefaultGraphicsCardPattern[] = "/dev/dri/card%d";
+const char kVgemSysCardPath[] = "/sys/bus/platform/devices/vgem/drm/";
 
 const char* kDisplayActionString[] = {
     "ADD",
     "REMOVE",
     "CHANGE",
 };
 
+// VGEM fd is a /dev/dri device but we cannot know in advance which one, for
+// that we inspect the /sys/.../vgem/.../cardX, if we find one such card, then
+// VGEM is present in the system and we can reuse the index.
+std::string GetVgemCardPath() {
+  static std::string vgem_card_path;
+  static base::ThreadChecker checker;
+  DCHECK(checker.CalledOnValidThread());
+  if (!vgem_card_path.empty())

[reveman, 2015/05/12 13:47:01]

Is this VgemCardPath really supposed to be a singleton? Please use LazyInstance
instead to avoid a race here and make it clear how this works.

[dshwang, 2015/05/12 14:11:42]

I believe it's singleton. +zachr

However, this code's purpose is just to run below while statement only once. I
see, I'll use LazyInstance.

+    return vgem_card_path;
+
+  base::FileEnumerator file_iter(
+      base::FilePath::FromUTF8Unsafe(kVgemSysCardPath), false,
+      base::FileEnumerator::DIRECTORIES, FILE_PATH_LITERAL("card*"));
+
+  while (!file_iter.Next().empty()) {
+    // Inspect the card%d directories in the directory and extract the index.
+    std::string name(file_iter.GetInfo().GetName().BaseName().MaybeAsASCII());
+    base::TrimString(name, "card", &name);
+    errno = 0;
+    const int device_index = strtol(name.c_str(), nullptr, 10);
+    DLOG_IF(ERROR, errno != 0) << "Error extracting integer from " << name;
+    if (errno != 0)
+      return std::string();
+
+    vgem_card_path =
+        base::StringPrintf(kDefaultGraphicsCardPattern, device_index);
+    DVLOG(1) << "VGEM card path is " << vgem_card_path;
+    break;
+  }
+  return vgem_card_path;
+}
+
 void OpenDeviceOnWorkerThread(
     const base::FilePath& path,
     const scoped_refptr<base::TaskRunner>& reply_runner,
     const OnOpenDeviceReplyCallback& callback) {
+  bool is_vgem = path.MaybeAsASCII() == GetVgemCardPath();
   scoped_ptr<DrmDeviceHandle> handle(new DrmDeviceHandle());
-  handle->Initialize(path);
+  handle->Initialize(path, is_vgem);
   reply_runner->PostTask(
       FROM_HERE, base::Bind(callback, path, base::Passed(handle.Pass())));
 }
 
 void CloseDeviceOnWorkerThread(
     scoped_ptr<DrmDeviceHandle> handle,
     const scoped_refptr<base::TaskRunner>& reply_runner,
     const base::Closure& callback) {
   handle.reset();
   reply_runner->PostTask(FROM_HERE, callback);
@@ skipping 48 matching lines @@
       primary_graphics_card_path_(GetPrimaryDisplayCardPath()),
       has_dummy_display_(false),
       task_pending_(false),
       weak_ptr_factory_(this) {
   {
     // First device needs to be treated specially. We need to open this
     // synchronously since the GPU process will need it to initialize the
     // graphics state.
     base::ThreadRestrictions::ScopedAllowIO allow_io;
     scoped_ptr<DrmDeviceHandle> handle(new DrmDeviceHandle());
-    if (!handle->Initialize(primary_graphics_card_path_)) {
+    if (!handle->Initialize(primary_graphics_card_path_, false)) {
       LOG(FATAL) << "Failed to open primary graphics card";
       return;
     }
     drm_devices_.add(primary_graphics_card_path_, handle.Pass());
   }
 
   device_manager_->AddObserver(this);
   proxy_->RegisterHandler(this);
 
   DisplaySnapshot_Params params;
@@ skipping 170 matching lines @@
         break;
     }
   }
 }
 
 void DrmDisplayHostManager::OnAddGraphicsDevice(
     const base::FilePath& path,
     scoped_ptr<DrmDeviceHandle> handle) {
   if (handle->IsValid()) {
     base::ScopedFD file = handle->Duplicate();
+    bool is_vgem = handle->IsVgem();
     drm_devices_.add(path, handle.Pass());
     proxy_->Send(new OzoneGpuMsg_AddGraphicsDevice(
-        path, base::FileDescriptor(file.Pass())));
+        path, base::FileDescriptor(file.Pass()), is_vgem));
     NotifyDisplayDelegate();
   }
 
   task_pending_ = false;
   ProcessEvent();
 }
 
 void DrmDisplayHostManager::OnUpdateGraphicsDevice() {
   NotifyDisplayDelegate();
   task_pending_ = false;
   ProcessEvent();
 }
 
 void DrmDisplayHostManager::OnRemoveGraphicsDevice(const base::FilePath& path) {
   proxy_->Send(new OzoneGpuMsg_RemoveGraphicsDevice(path));
   NotifyDisplayDelegate();
   task_pending_ = false;
   ProcessEvent();
 }
 
 void DrmDisplayHostManager::OnChannelEstablished(
     int host_id,
     scoped_refptr<base::SingleThreadTaskRunner> send_runner,
     const base::Callback<void(IPC::Message*)>& send_callback) {
   auto it = drm_devices_.find(primary_graphics_card_path_);
   DCHECK(it != drm_devices_.end());
   // Send the primary device first since this is used to initialize graphics
   // state.
   proxy_->Send(new OzoneGpuMsg_AddGraphicsDevice(
-      it->first, base::FileDescriptor(it->second->Duplicate())));
+      it->first, base::FileDescriptor(it->second->Duplicate()),
+      it->second->IsVgem()));
 
   for (auto pair : drm_devices_) {
     if (pair.second->IsValid() && pair.first != primary_graphics_card_path_) {
       proxy_->Send(new OzoneGpuMsg_AddGraphicsDevice(
-          pair.first, base::FileDescriptor(pair.second->Duplicate())));
+          pair.first, base::FileDescriptor(pair.second->Duplicate()),
+          it->second->IsVgem()));
     }
   }
 
   device_manager_->ScanDevices(this);
   NotifyDisplayDelegate();
 }
 
 void DrmDisplayHostManager::OnChannelDestroyed(int host_id) {
   // If the channel got destroyed in the middle of a configuration then just
   // respond with failure.
@@ skipping 77 matching lines @@
     const GetDisplaysCallback& callback) const {
   callback.Run(displays_.get());
 }
 
 void DrmDisplayHostManager::NotifyDisplayDelegate() const {
   if (delegate_)
     delegate_->OnConfigurationChanged();
 }
 
 }  // namespace ui