drm: Make DrmDisplayHostManager handle VGEM fd by itself.

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 d22752717435b5d761cab96499d904cfab44477c..473970a4f9c6585c579a4928d8bcf69dc6e37576 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 kVgemDevDriCardPath[] = "/dev/dri/";
+const char kVgemSysCardPath[] = "/sys/bus/platform/devices/vgem/drm/";

[vignatti (out of this project), 2015/05/26 18:28:34]

note that this only works on CrOS. In other Linux variants, platform device is
not initialized and there won't be a sysfs exported information about vgem.

(I'm more and more having trouble to hack Ozone GBM in regular Linuxes... I
think it's time to make a  definitive move to CrOS :/)

 
 const char* kDisplayActionString[] = {
     "ADD",
@@ -75,6 +78,23 @@ base::FilePath GetPrimaryDisplayCardPath() {
   return base::FilePath();
 }
 
+base::FilePath GetVgemCardPath() {
+  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 filename.
+    std::string vgem_card_path =
+        kVgemDevDriCardPath +
+        file_iter.GetInfo().GetName().BaseName().MaybeAsASCII();
+    DVLOG(1) << "VGEM card path is " << vgem_card_path;
+    return base::FilePath(vgem_card_path);
+  }
+  DVLOG(1) << "Don't support VGEM";
+  return base::FilePath();
+}
+
 class FindDisplaySnapshotById {
  public:
   FindDisplaySnapshotById(int64_t display_id) : display_id_(display_id) {}
@@ -109,6 +129,11 @@ DrmDisplayHostManager::DrmDisplayHostManager(DrmGpuPlatformSupportHost* proxy,
       return;
     }
     drm_devices_.insert(primary_graphics_card_path_);
+
+    vgem_card_path_ = GetVgemCardPath();
+    vgem_card_device_file_ = base::File(
+        vgem_card_path_,
+        base::File::FLAG_OPEN | base::File::FLAG_READ | base::File::FLAG_WRITE);
   }
 
   device_manager_->AddObserver(this);
@@ -229,6 +254,8 @@ void DrmDisplayHostManager::ProcessEvent() {
             << " for " << event.path.value();
     switch (event.action_type) {
       case DeviceEvent::ADD:
+        if (event.path == vgem_card_path_)
+          continue;
         if (drm_devices_.find(event.path) == drm_devices_.end()) {
           task_pending_ = base::WorkerPool::PostTask(
               FROM_HERE,
@@ -248,6 +275,7 @@ void DrmDisplayHostManager::ProcessEvent() {
       case DeviceEvent::REMOVE:
         DCHECK(event.path != primary_graphics_card_path_)
             << "Removing primary graphics card";
+        DCHECK(event.path != vgem_card_path_) << "Removing VGEM device";
         auto it = drm_devices_.find(event.path);
         if (it != drm_devices_.end()) {
           task_pending_ = base::ThreadTaskRunnerHandle::Get()->PostTask(