Add gamepad data fetcher for Linux

content/browser/gamepad/platform_data_fetcher_linux.cc

+// Copyright (c) 2011 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 "content/browser/gamepad/platform_data_fetcher_linux.h"
+
+#include <dlfcn.h>
+#include <fcntl.h>
+#include <libudev.h>
+#include <linux/joystick.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "base/debug/trace_event.h"
+#include "base/eintr_wrapper.h"
+#include "base/message_loop.h"
+#include "base/stringprintf.h"
+#include "base/string_util.h"
+#include "base/utf_string_conversions.h"
+#include "content/common/gamepad_hardware_buffer.h"
+
+namespace content {
+
+using WebKit::WebGamepad;
+using WebKit::WebGamepads;
+
+GamepadPlatformDataFetcherLinux::GamepadPlatformDataFetcherLinux() {
+  for (size_t i = 0; i < arraysize(device_fds_); ++i)
+    device_fds_[i] = -1;
+
+  udev_ = udev_new();
+
+  monitor_ = udev_monitor_new_from_netlink(udev_, "udev");
+  udev_monitor_filter_add_match_subsystem_devtype(monitor_, "input", NULL);
+  udev_monitor_enable_receiving(monitor_);
+  monitor_fd_ = udev_monitor_get_fd(monitor_);
+  MessageLoopForIO::current()->WatchFileDescriptor(monitor_fd_, true,
+      MessageLoopForIO::WATCH_READ, &monitor_watcher_, this);
+
+  EnumerateDevices();
+}
+
+void GamepadPlatformDataFetcherLinux::GetGamepadData(WebGamepads* pads, bool) {
+  TRACE_EVENT0("GAMEPAD", "GetGamepadData");
+
+  data_.length = WebGamepads::itemsLengthCap;
+
+  // Update our internal state.
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (device_fds_[i] >= 0) {
+      ReadDeviceData(i);
+    }
+  }
+
+  // Copy to the current state to the output buffer, using the mapping
+  // function, if there is one available.
+  pads->length = data_.length;
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (mappers_[i])
+      mappers_[i](data_.items[i], &pads->items[i]);
+    else
+      pads->items[i] = data_.items[i];
+  }
+}
+
+void GamepadPlatformDataFetcherLinux::OnFileCanReadWithoutBlocking(int fd) {
+  // Events occur when devices attached to the system are added, removed, or
+  // change state. udev_monitor_receive_device() will return a device object
+  // representing the device which changed and what type of change occured.
+  DCHECK(monitor_fd_ == fd);
+  udev_device* dev = udev_monitor_receive_device(monitor_);
+  RefreshDevice(dev);
+  udev_device_unref(dev);
+}
+
+void GamepadPlatformDataFetcherLinux::OnFileCanWriteWithoutBlocking(int fd) {
+}
+
+GamepadPlatformDataFetcherLinux::~GamepadPlatformDataFetcherLinux() {
+  monitor_watcher_.StopWatchingFileDescriptor();
+  udev_unref(udev_);
+}

[Ryan Sleevi, 2011/12/19 22:51:58]

BUG? Did you mean to close() device_fds_ ?

[scottmg, 2011/12/19 23:23:53]

Done.

+
+bool GamepadPlatformDataFetcherLinux::IsGamepad(
+    udev_device* dev,
+    size_t& index,
+    std::string& path) {
+  if (!udev_device_get_property_value(dev, "ID_INPUT_JOYSTICK"))
+    return false;
+
+  const char* node_path = udev_device_get_devnode(dev);
+  if (!node_path)
+    return false;
+
+  static const char kJoystickRoot[] = "/dev/input/js";
+  bool is_gamepad =
+      strncmp(kJoystickRoot, node_path, sizeof(kJoystickRoot) - 1) == 0;
+  if (is_gamepad) {
+    index = strtoul(&node_path[sizeof(kJoystickRoot) - 1], NULL, 10);

[Ryan Sleevi, 2011/12/19 22:51:58]

See base/string_number_conversions.h

It can return a bool for any invalid inputs.

[scottmg, 2011/12/19 23:23:53]

Done.

+    if (index < 0 || index >= WebGamepads::itemsLengthCap)
+      return false;
+    path = std::string(node_path);
+  }
+  return is_gamepad;
+}
+
+// Used during enumeration, and monitor notifications.
+void GamepadPlatformDataFetcherLinux::RefreshDevice(udev_device* dev) {
+  size_t index;
+  std::string node_path;
+  if (IsGamepad(dev, index, node_path)) {
+    int& device_fd = device_fds_[index];
+    WebGamepad& pad = data_.items[index];
+    GamepadStandardMappingFunction& mapper = mappers_[index];
+
+    // The device pointed to by dev contains information about the input
+    // device. In order to get the information about the USB device, get the
+    // parent device with the subsystem/devtype pair of "usb"/"usb_device".
+    // This function walks up the tree several levels.
+    dev = udev_device_get_parent_with_subsystem_devtype(
+        dev,
+        "usb",
+        "usb_device");
+    if (!dev) {
+      // Unable to get device information, don't use this device.
+      device_fd = -1;
+      pad.connected = false;
+      return;
+    }
+
+    device_fd = HANDLE_EINTR(open(node_path.c_str(), O_RDONLY | O_NONBLOCK));

[Ryan Sleevi, 2011/12/19 22:51:58]

BUG?

If this node path was already opened by a previous call to RefreshDevice, this
means the descriptor is leaked, correct?

Alternatively, if RefreshDevice is called on an existing open connection, line
126 could also leak, correct?

[scottmg, 2011/12/19 23:23:53]

Done.

+    if (device_fd < 0) {
+      // Unable to open device, don't use.
+      pad.connected = false;
+      return;
+    }
+
+    const char* vendor_id = udev_device_get_sysattr_value(dev, "idVendor");
+    const char* product_id = udev_device_get_sysattr_value(dev, "idProduct");
+    mapper = GetGamepadStandardMappingFunction(vendor_id, product_id);
+
+    const char* manufacturer =
+        udev_device_get_sysattr_value(dev, "manufacturer");
+    const char* product = udev_device_get_sysattr_value(dev, "product");
+
+    // Driver returns utf-8 strings here, so combine in utf-8 and then convert
+    // to WebUChar to build the id string.
+    std::string id;
+    if (mapper) {
+      id = base::StringPrintf("%s %s (STANDARD GAMEPAD)",
+                         manufacturer,
+                         product);
+    } else {
+      id = base::StringPrintf("%s %s (Vendor: %s Product: %s)",
+          manufacturer,
+          product,
+          vendor_id,
+          product_id);
+    }
+    TruncateUTF8ToByteSize(id, WebGamepad::idLengthCap - 1, &id);
+    string16 tmp16 = UTF8ToUTF16(id);
+    memset(pad.id, 0, sizeof(pad.id));
+    tmp16.copy(pad.id, sizeof(pad.id) - 1);

[Ryan Sleevi, 2011/12/19 22:51:58]

BUG:
tmp16.copy is copying characters, but you're providing byte size
(sizeof(pad.id))

You could use the arraysize() macro here to avoid this. Or use
WebGamepad::idLengthCap - 1

[scottmg, 2011/12/19 23:23:53]

Done.

+
+    pad.connected = true;
+  }
+}
+
+void GamepadPlatformDataFetcherLinux::EnumerateDevices() {
+  udev_enumerate* enumerate = udev_enumerate_new(udev_);
+  udev_enumerate_add_match_subsystem(enumerate, "input");
+  udev_enumerate_scan_devices(enumerate);
+
+  udev_list_entry* devices = udev_enumerate_get_list_entry(enumerate);
+  for (udev_list_entry* dev_list_entry = devices;
+       dev_list_entry != NULL;
+       dev_list_entry = udev_list_entry_get_next(dev_list_entry)) {
+    // Get the filename of the /sys entry for the device and create a
+    // udev_device object (dev) representing it
+    const char* path = udev_list_entry_get_name(dev_list_entry);
+    udev_device* dev = udev_device_new_from_syspath(udev_, path);
+    RefreshDevice(dev);
+    udev_device_unref(dev);
+  }
+  // Free the enumerator object
+  udev_enumerate_unref(enumerate);
+}
+
+void GamepadPlatformDataFetcherLinux::ReadDeviceData(size_t index) {
+  int& fd = device_fds_[index];
+  WebGamepad& pad = data_.items[index];
+  DCHECK(fd >= 0);
+
+  js_event event;
+  while (HANDLE_EINTR(read(fd, &event, sizeof(struct js_event)) > 0)) {
+    size_t item = event.number;
+    if (event.type & JS_EVENT_AXIS) {
+      if (item >= WebGamepad::axesLengthCap)
+        continue;
+      pad.axes[item] = event.value / 32767.f;
+      if (item >= pad.axesLength)
+        pad.axesLength = item + 1;
+    } else if (event.type & JS_EVENT_BUTTON) {
+      if (item >= WebGamepad::buttonsLengthCap)
+        continue;
+      pad.buttons[item] = event.value ? 1.0 : 0.0;
+      if (item >= pad.buttonsLength)
+        pad.buttonsLength = item + 1;
+    }
+    pad.timestamp = event.time;
+  }
+}
+
+
+}  // namespace content