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 "base/debug/trace_event.h"
+#include "base/string_util.h"
+#include "base/utf_string_conversions.h"
+#include "content/common/gamepad_hardware_buffer.h"
+
+#include <dlfcn.h>

[Ryan Sleevi, 2011/12/17 04:31:14]

style nit: C headers before Chromium headers

[scottmg, 2011/12/19 19:41:45]

Done.

+#include <fcntl.h>
+#include <libudev.h>
+#include <linux/joystick.h>
+#include <sys/stat.h>
+#include <sys/types.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_);
+
+  EnumerateDevices();
+}
+
+
+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 = strncmp(kJoystickRoot, node_path, sizeof(kJoystickRoot) - 1) == 0;

[Ryan Sleevi, 2011/12/17 04:31:14]

nit: is -> is_gamepad ?

[scottmg, 2011/12/19 19:41:45]

Done.

+  if (is) {
+    index = node_path[sizeof(kJoystickRoot) - 1] - '0';

[Ryan Sleevi, 2011/12/17 04:31:14]

BUG? It seems possible for there to be a /dev/input/js10, /dev/input/js11 or
more (at least, judging from quickly Google searching)

What impact, if any, will that have on this code? 10 == 1 seems like it could
cause trouble?

[scottmg, 2011/12/19 19:41:45]

Done.

+    if (index < 0 || index >= WebGamepads::itemsLengthCap)
+      return false;
+    path = std::string(node_path);
+  }
+  return is;
+}
+
+// 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 = open(node_path.c_str(), O_RDONLY | O_NONBLOCK);

[Ryan Sleevi, 2011/12/17 04:31:14]

Normally these calls are wrapped in the HANDLE_EINTR macro (at least, liberally
throughout base)

Does that need to be something you do here as well?

[scottmg, 2011/12/19 19:41:45]

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.

[Ryan Sleevi, 2011/12/17 04:31:14]

BUG? Because they're UTF-8 strings, what risk is there, if any, if the strings
are overlong and thus split on an invalid sequence?

Also, is idLengthCap the length of characters or bytes (my guess, characters?)
Would seem to matter here as well.

Perhaps you should use base::StringPrintF to take in the whole string as UTF-8,
then run through UTF8toUTF16 to convert to WebUChar/UTF-16, and then split as
appropriate.

[scottmg, 2011/12/19 19:41:45]

Done. There's no Truncate for utf16 in base so I (conservatively) truncated the
utf-8 version.

+    char tmp[WebGamepad::idLengthCap];
+    if (mapper) {
+      base::snprintf(tmp,
+                     sizeof(tmp),
+                     "%s %s (STANDARD GAMEPAD)",
+                     manufacturer,
+                     product);
+    } else {
+      base::snprintf(tmp,
+                     sizeof(tmp),
+                     "%s %s (Vendor: %s Product: %s)",
+                     manufacturer,
+                     product,
+                     vendor_id,
+                     product_id);
+    }
+    string16 tmp16 = UTF8ToUTF16(tmp);
+    memset(pad.id, 0, sizeof(pad.id));
+    tmp16.copy(pad.id, sizeof(pad.id) - 1);
+
+    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);
+}
+
+GamepadPlatformDataFetcherLinux::~GamepadPlatformDataFetcherLinux() {

[Ryan Sleevi, 2011/12/17 04:31:14]

style nit: There was a big clean-up effort to have all of the .cc files match
the declaration order as in the header files (yay clang!). 

It would be nice as a style nit to be able to correct that here and elsewhere in
this CL.

[scottmg, 2011/12/19 19:41:45]

Done.

+  udev_unref(udev_);
+}
+
+void GamepadPlatformDataFetcherLinux::CheckForAddRemoveEvents() {
+  // Poll for udev events. 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.
+  //
+  // The select() system call is used to ensure that the call to
+  // udev_monitor_receive_device() will not block.
+  fd_set fds;
+  struct timeval tv;
+  FD_ZERO(&fds);
+  FD_SET(monitor_fd_, &fds);
+  tv.tv_sec = 0;
+  tv.tv_usec = 0;
+
+  // Check if our file descriptor has received data.
+  if (select(monitor_fd_ + 1, &fds, NULL, NULL, &tv) > 0

[Ryan Sleevi, 2011/12/17 04:31:14]

HANDLE_EINTR(select( ?

Is there a reason not to use base::MessagePumpLibEvent::FileDescriptorWatcher?
Certainly seems more Chromium-y (at least, excluding CrOS-specific code)

[scottmg, 2011/12/19 19:41:45]

Done.

+      && FD_ISSET(monitor_fd_, &fds)) {
+    // Make the call to receive the device.
+    // select() ensured that this will not block.
+    udev_device* dev = udev_monitor_receive_device(monitor_);
+    RefreshDevice(dev);
+    udev_device_unref(dev);
+  }
+}
+
+void GamepadPlatformDataFetcherLinux::ReadDeviceData(size_t index) {
+  int& fd = device_fds_[index];
+  WebGamepad& pad = data_.items[index];
+  DCHECK(fd >= 0);
+
+  js_event event;
+  while (read(fd, &event, sizeof(struct js_event)) > 0) {

[Ryan Sleevi, 2011/12/17 04:31:14]

HANDLE_EINTR(read( ?

[scottmg, 2011/12/19 19:41:45]

Done.

+    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;
+  }
+}
+
+void GamepadPlatformDataFetcherLinux::GetGamepadData(WebGamepads* pads, bool) {
+  TRACE_EVENT0("GAMEPAD", "GetGamepadData");
+
+  data_.length = WebGamepads::itemsLengthCap;
+
+  CheckForAddRemoveEvents();
+
+  // 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];
+  }
+}
+
+}  // namespace content