HID: Support top-level collection usages in device info.

device/hid/hid_service_linux.cc

Index: device/hid/hid_service_linux.cc
diff --git a/device/hid/hid_service_linux.cc b/device/hid/hid_service_linux.cc
index aeaeb19aeae31a0f8957b46afdf9a10accccde45..86342c9226e64318463b361d80a7b98d11f15072 100644
--- a/device/hid/hid_service_linux.cc
+++ b/device/hid/hid_service_linux.cc
@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <libudev.h>
+#include <linux/hidraw.h>
+#include <sys/ioctl.h>
+
 #include <stdint.h>
 
 #include <string>
-#include <vector>
 
 #include "base/bind.h"
+#include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/platform_file.h"
 #include "base/stl_util.h"
@@ -17,6 +19,7 @@
 #include "base/strings/string_split.h"
 #include "device/hid/hid_connection_linux.h"
 #include "device/hid/hid_device_info.h"
+#include "device/hid/hid_report_descriptor.h"
 #include "device/hid/hid_service_linux.h"
 #include "device/hid/udev_common.h"
 
@@ -25,7 +28,7 @@ namespace device {
 namespace {
 
 const char kHIDSubSystem[] = "hid";
-
+const char kHidrawSubsystem[] = "hidraw";
 const char kHIDID[] = "HID_ID";
 const char kHIDName[] = "HID_NAME";
 const char kHIDUnique[] = "HID_UNIQ";
@@ -48,8 +51,16 @@ scoped_refptr<HidConnection> HidServiceLinux::Connect(
   ScopedUdevDevicePtr device =
       DeviceMonitorLinux::GetInstance()->GetDeviceFromPath(
           device_info.device_id);
-  if (device)
-    return new HidConnectionLinux(device_info, device.Pass());
+
+  if (device) {
+    std::string dev_node;
+    if (!FindHidrawDevNode(device.get(), &dev_node)) {
+      LOG(ERROR) << "Cannot open HID device as hidraw device.";
+      return NULL;
+    }
+    return new HidConnectionLinux(device_info, dev_node);
+  }
+
   return NULL;
 }
 
@@ -101,6 +112,43 @@ void HidServiceLinux::OnDeviceAdded(udev_device* device) {
   if (str_property != NULL)
     device_info.product_name = str_property;
 
+  std::string dev_node;
+  if (!FindHidrawDevNode(device, &dev_node)) {
+    LOG(ERROR) << "Cannot open HID device as hidraw device.";
+    return;
+  }
+
+  int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
+
+  base::File device_file(base::FilePath(dev_node), flags);
+  if (!device_file.IsValid()) {
+    LOG(ERROR) << device_file.error_details();
+    return;
+  }
+
+  int desc_size = 0;
+  int res = ioctl(device_file.GetPlatformFile(), HIDIOCGRDESCSIZE, &desc_size);
+  if (res < 0) {
+    LOG(ERROR) << "HIDIOCGRDESCSIZE failed.";
+    device_file.Close();
+    return;
+  }
+
+  hidraw_report_descriptor rpt_desc;
+  rpt_desc.size = desc_size;
+
+  res = ioctl(device_file.GetPlatformFile(), HIDIOCGRDESC, &rpt_desc);
+  if (res < 0) {
+    LOG(ERROR) << "HIDIOCGRDESC failed.";
+    device_file.Close();
+    return;
+  }
+
+  device_file.Close();
+
+  HidReportDescriptor report_descriptor(rpt_desc.value, rpt_desc.size);
+  report_descriptor.GetTopLevelCollections(&device_info.usages);
+
   AddDevice(device_info);
 }
 
@@ -110,4 +158,44 @@ 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 dev