Monitor udev for hidraw devices instead of hid devices.

Watching for new hid devices is racy because the hidraw device rules are
still running. Fix the race by explicitly waiting for the hidraw device
add event. The properties needed from the hid device can be gotten by
fetching the parent of the hidraw device from the sysfs tree.

BUG=394200

Review URL: https://codereview.chromium.org/396993010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283810 0039d316-1c4b-4281-b951-d872f2087c98

device/hid/hid_service_linux.cc

@@ -27,7 +27,6 @@ namespace device {
 
 namespace {
 
-const char kHIDSubSystem[] = "hid";
 const char kHidrawSubsystem[] = "hidraw";
 const char kHIDID[] = "HID_ID";
 const char kHIDName[] = "HID_NAME";
@@ -53,11 +52,7 @@ scoped_refptr<HidConnection> HidServiceLinux::Connect(
           device_info.device_id);
 
   if (device) {
-    std::string dev_node;
-    if (!FindHidrawDevNode(device.get(), &dev_node)) {
-      LOG(ERROR) << "Cannot open HID device as hidraw device.";
-      return NULL;
-    }
+    std::string dev_node = udev_device_get_devnode(device.get());
     return new HidConnectionLinux(device_info, dev_node);
   }
 
@@ -77,7 +72,7 @@ void HidServiceLinux::OnDeviceAdded(udev_device* device) {
   if (!device_path)
     return;
   const char* subsystem = udev_device_get_subsystem(device);
-  if (!subsystem || strcmp(subsystem, kHIDSubSystem) != 0)
+  if (!subsystem || strcmp(subsystem, kHidrawSubsystem) != 0)
     return;
 
   HidDeviceInfo device_info;
@@ -86,7 +81,12 @@ void HidServiceLinux::OnDeviceAdded(udev_device* device) {
   uint32_t int_property = 0;
   const char* str_property = NULL;
 
-  const char* hid_id = udev_device_get_property_value(device, kHIDID);
+  udev_device *parent = udev_device_get_parent(device);
+  if (!parent) {
+    return;
+  }
+
+  const char* hid_id = udev_device_get_property_value(parent, kHIDID);
   if (!hid_id)
     return;
 
@@ -104,21 +104,16 @@ void HidServiceLinux::OnDeviceAdded(udev_device* device) {
     device_info.product_id = int_property;
   }
 
-  str_property = udev_device_get_property_value(device, kHIDUnique);
+  str_property = udev_device_get_property_value(parent, kHIDUnique);
   if (str_property != NULL)
     device_info.serial_number = str_property;
 
-  str_property = udev_device_get_property_value(device, kHIDName);
+  str_property = udev_device_get_property_value(parent, kHIDName);
   if (str_property != NULL)
     device_info.product_name = str_property;
 
-  std::string dev_node;
-  if (!FindHidrawDevNode(device, &dev_node)) {
-    LOG(ERROR) << "Cannot find device node for HID device.";
-    return;
-  }
-
-  int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
+  const std::string dev_node = udev_device_get_devnode(device);
+  const int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
 
   base::File device_file(base::FilePath(dev_node), flags);
   if (!device_file.IsValid()) {
@@ -162,44 +157,4 @@ void HidServiceLinux::OnDeviceRemoved(udev_device* device) {
     RemoveDevice(device_path);
 }
 
-bool HidServiceLinux::FindHidrawDevNode(udev_device* parent,
-                                        std::string* result) {
-  udev* udev = udev_device_get_udev(parent);
-  if (!udev) {
-    return false;
-  }
-  ScopedUdevEnumeratePtr enumerate(udev_enumerate_new(udev));
-  if (!enumerate) {
-    return false;
-  }
-  if (udev_enumerate_add_match_subsystem(enumerate.get(), kHidrawSubsystem)) {
-    return false;
-  }
-  if (udev_enumerate_scan_devices(enumerate.get())) {
-    return false;
-  }
-  std::string parent_path(udev_device_get_devpath(parent));
-  if (parent_path.length() == 0 || *parent_path.rbegin() != '/')
-    parent_path += '/';
-  udev_list_entry* devices = udev_enumerate_get_list_entry(enumerate.get());
-  for (udev_list_entry* i = devices; i != NULL;
-       i = udev_list_entry_get_next(i)) {
-    ScopedUdevDevicePtr hid_dev(
-        udev_device_new_from_syspath(udev, udev_list_entry_get_name(i)));
-    const char* raw_path = udev_device_get_devnode(hid_dev.get());
-    std::string device_path = udev_device_get_devpath(hid_dev.get());
-    if (raw_path &&
-        !device_path.compare(0, parent_path.length(), parent_path)) {
-      std::string sub_path = device_path.substr(parent_path.length());
-      if (sub_path.substr(0, sizeof(kHidrawSubsystem) - 1) ==
-          kHidrawSubsystem) {
-        *result = raw_path;
-        return true;
-      }
-    }
-  }
-
-  return false;
-}
-
 }  // namespace device

device/hid/hid_service_linux.h

@@ -32,8 +32,6 @@ class HidServiceLinux : public HidService,
  private:
   virtual ~HidServiceLinux();
 
-  static bool FindHidrawDevNode(udev_device* parent, std::string* result);
-
   DISALLOW_COPY_AND_ASSIGN(HidServiceLinux);
 };