drm: GPU process manages VGEM fd.

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

Index: ui/ozone/platform/drm/host/drm_display_host_manager.cc
diff --git a/ui/ozone/platform/drm/host/drm_display_host_manager.cc b/ui/ozone/platform/drm/host/drm_display_host_manager.cc
index 93d43e2467de430ae2cec6ce1655f6eb33dd403d..874912b7e6347ffe1b0ec13aa1a5168094972b1a 100644
--- a/ui/ozone/platform/drm/host/drm_display_host_manager.cc
+++ b/ui/ozone/platform/drm/host/drm_display_host_manager.cc
@@ -8,6 +8,7 @@
 #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"
@@ -31,6 +32,8 @@ 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/";
+base::LazyInstance<std::string> kVgemCardPath;

[spang, 2015/05/12 17:20:38]

Please don't add state to the global scope. Instead, find an appropriate object
to own this.

[dshwang, 2015/05/12 17:48:02]

I see. I move this to member of this class.

[dshwang, 2015/05/13 13:09:00]

Done.

 
 const char* kDisplayActionString[] = {
     "ADD",
@@ -38,12 +41,42 @@ const char* kDisplayActionString[] = {
     "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() {
+  if (!kVgemCardPath.Get().empty())
+    return kVgemCardPath.Get();
+
+  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);

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

Rather than extracting the interger, why not just append the base name to
"/dev/dri/" to get the final path?

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

good point. I'll update.

[dshwang, 2015/05/13 13:09:00]

Done.

+    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();
+
+    kVgemCardPath.Get() =
+        base::StringPrintf(kDefaultGraphicsCardPattern, device_index);
+    DVLOG(1) << "VGEM card path is " << kVgemCardPath.Get();
+    break;
+  }
+  return kVgemCardPath.Get();
+}
+
 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())));
 }
@@ -112,7 +145,7 @@ DrmDisplayHostManager::DrmDisplayHostManager(DrmGpuPlatformSupportHost* proxy,
     // 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;
     }
@@ -303,9 +336,10 @@ void DrmDisplayHostManager::OnAddGraphicsDevice(
     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();
   }
 
@@ -335,12 +369,14 @@ void DrmDisplayHostManager::OnChannelEstablished(
   // 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()));
     }
   }