ozone: evdev: Add gamepad support

ui/events/ozone/evdev/gamepad_event_converter_evdev.cc

+// Copyright 2017 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 "ui/events/ozone/evdev/gamepad_event_converter_evdev.h"
+
+#include <errno.h>
+#include <linux/input.h>
+#include <stddef.h>
+
+#include "base/trace_event/trace_event.h"
+#include "ui/events/event_utils.h"
+#include "ui/events/ozone/evdev/device_event_dispatcher_evdev.h"
+#include "ui/events/ozone/evdev/scoped_input_device.h"
+#include "ui/events/ozone/gamepad/gamepad_event.h"
+#include "ui/events/ozone/gamepad/gamepad_provider_ozone.h"
+#include "ui/events/ozone/gamepad/webgamepad_constants.h"
+
+namespace ui {
+
+GamepadEventConverterEvdev::GamepadEventConverterEvdev(
+    ScopedInputDevice fd,
+    base::FilePath path,
+    int id,
+    const EventDeviceInfo& devinfo,
+    DeviceEventDispatcherEvdev* dispatcher)
+    : EventConverterEvdev(fd.get(),
+                          path,
+                          id,
+                          devinfo.device_type(),
+                          devinfo.name(),
+                          devinfo.vendor_id(),
+                          devinfo.product_id()),
+      will_send_frame_(false),
+      input_device_fd_(std::move(fd)),
+      dispatcher_(dispatcher) {
+  // In order to map gamepad, we have to save the abs_info from device_info
+  // and get the gamepad_mapping.
+  for (int code = 0; code < ABS_CNT; ++code) {
+    abs_info_[code] = devinfo.GetAbsInfoByCode(code);
+    if (devinfo.HasAbsEvent(code)) {
+      // If fuzz was reported as zero, it will be set to flat * 0.25f. It is the
+      // same thing done in Android InputReader.cpp. See:
+      // frameworks/native/services/inputflinger/InputReader.cpp line 6988 for
+      // more details.
+      if (abs_info_[code].fuzz == 0) {
+        abs_info_[code].fuzz = abs_info_[code].flat * 0.25f;
+      }
+    }
+  }
+  mapper_ = GetGamepadMapper(devinfo.vendor_id(), devinfo.product_id());
+}
+
+GamepadEventConverterEvdev::~GamepadEventConverterEvdev() {
+  DCHECK(!enabled_);
+}
+
+bool GamepadEventConverterEvdev::HasGamepad() const {
+  return true;
+}
+
+void GamepadEventConverterEvdev::OnFileCanReadWithoutBlocking(int fd) {
+  TRACE_EVENT1("evdev",
+               "GamepadEventConverterEvdev::OnFileCanReadWithoutBlocking", "fd",
+               fd);
+  while (true) {
+    input_event input;
+    ssize_t read_size = read(fd, &input, sizeof(input));
+    if (read_size != sizeof(input)) {
+      if (errno == EINTR || errno == EAGAIN)
+        return;
+      if (errno != ENODEV)
+        PLOG(ERROR) << "error reading device " << path_.value();
+      Stop();
+      return;
+    }
+
+    if (!enabled_)
+      return;
+
+    ProcessEvent(input);
+  }
+}
+void GamepadEventConverterEvdev::OnDisabled() {
+  ResetGamepad();
+}
+
+void GamepadEventConverterEvdev::ProcessEvent(const input_event& evdev_ev) {
+  // We may have missed Gamepad releases. Reset everything.
+  // If the event is sync, we send a frame.
+  if (evdev_ev.type == EV_SYN) {
+    if (evdev_ev.code == SYN_DROPPED) {
+      LOG(WARNING) << "kernel dropped input events";
+      ResyncGamepad();
+    } else if (evdev_ev.code == SYN_REPORT) {
+      OnSync(TimeTicksFromInputEvent(evdev_ev));
+    }
+    return;
+  }
+
+  GamepadEventType mapped_type;
+  uint16_t mapped_code;
+
+  bool found_map =
+      mapper_(evdev_ev.type, evdev_ev.code, &mapped_type, &mapped_code);
+
+  // If we cannot find a map for this event, it will be discarded.
+  if (!found_map) {
+    return;
+  }
+
+  // If it's btn -> btn mapping, we can send the event and return now.
+  if (mapped_type == GamepadEventType::BUTTON && evdev_ev.type == EV_KEY) {
+    OnButtonChange(mapped_code, evdev_ev.value,
+                   TimeTicksFromInputEvent(evdev_ev));
+    return;
+  }
+
+  double mapped_abs_value;
+
+  double mapped_abs_min = kWebGamepadJoystickMin;
+  double mapped_abs_max = kWebGamepadJoystickMax;
+  // If the mapped event is a trigger, we set the min and max to trigger
+  // min/max.
+  if (mapped_code == WG_BUTTON_LT || mapped_code == WG_BUTTON_RT) {
+    mapped_abs_min = kWebGamepadTriggerMin;
+    mapped_abs_max = kWebGamepadTriggerMax;
+  }
+
+  // Code is out of ABS_MAX. This should not happen, but we don't want a gamepad
+  // reporting wrong values break the code.
+  if (evdev_ev.code < 0 || evdev_ev.code > ABS_MAX) {
+    return;
+  }
+
+  struct input_absinfo& abs_info = abs_info_[evdev_ev.code];
+  // To remove noise, the value must change at least by fuzz.
+  if (evdev_ev.value > abs_info.value - abs_info.fuzz &&

[spang, 2017/05/03 22:00:37]

Can't this fuzzing prevent the value from returning zero? That seems bad.

[jkwang, 2017/05/05 00:07:45]

Done.

+      evdev_ev.value < abs_info.value + abs_info.fuzz) {
+    return;
+  }
+
+  // Save the old value for later use.
+  int old_value = abs_info.value;
+  abs_info.value = evdev_ev.value;
+
+  double scale =
+      (mapped_abs_max - mapped_abs_min) / (abs_info.maximum - abs_info.minimum);
+  double offset = (abs_info.maximum + abs_info.minimum) /

[spang, 2017/05/03 22:00:38]

offset and scale can be pre-calculated. If you do that up front I don't think
trigger needs to be special here.

I think at a high level what you should do is replace abs_info_ with a new local
"struct Axis" so that you can add new stuff there such as the scale factor.
Then, pre-calculate the values you need here in Initialize().

[jkwang, 2017/05/05 00:07:45]

Done.

+                  (mapped_abs_max - mapped_abs_min) * scale * mapped_abs_min;
+
+  double scaled_flat = abs_info.flat * scale;
+
+  mapped_abs_value = evdev_ev.value * scale + offset;
+
+  // As the definition of linux input_absinfo.flat, value within the range of
+  // flat should be seen as zero.
+  if (mapped_abs_value < scaled_flat && mapped_abs_value > -scaled_flat) {
+    mapped_abs_value = 0.0;
+  }
+
+  // If the mapped type is abs, we can send it now.
+  if (mapped_type == GamepadEventType::AXIS) {
+    OnAbsChange(mapped_code, mapped_abs_value,
+                TimeTicksFromInputEvent(evdev_ev));
+    return;
+  }
+
+  // We need to map HAT to DPAD depend on the state of the axis.
+  if (mapped_code == kHAT_X) {
+    if (mapped_abs_value < 0.0 ||
+        (mapped_abs_value == 0.0 && old_value < abs_info.flat)) {

[spang, 2017/05/03 22:00:37]

It's hard to follow this because it mixes use of the the raw and transformed
values. If you can, please do the transform first, and do the rest of the
computations with those values, or do them last, and do the rest of the
computations with the raw values.

It's also hard to see that this button logic is safe in the sense that buttons
cannot become stuck, and it looks like a rapid change from positive to negative
or vice versa will get lost until the value changes again. How about something
like:

bool hat_left_press = (mapped_abs_value > threshold);
bool hat_right_press = (mapped_abs_value < -threshold);

if (hat_left_press != last_hat_left_press_) {
  OnButtonChange(WG_BUTTON_DPAD_LEFT, hat_left_press);
  last_hat_left_press_ = hat_left_press;
}

if (hat_right_press != last_hat_right_press_) {
  OnButtonChange(WG_BUTTON_DPAD_RIGHT, hat_right_press);
  last_hat_right_press_ = hat_right_press;
}

Finally, is using flat right here? This seems like it would be too sensitive.
device/gamepad is using 0.5.

[jkwang, 2017/05/05 00:07:45]

Done.

+      // If current HAT_X is < 0 or it was < 0 before, it's dpad left.
+      mapped_code = WG_BUTTON_DPAD_LEFT;
+    } else {
+      mapped_code = WG_BUTTON_DPAD_RIGHT;
+    }
+  } else if (mapped_code == kHAT_Y) {
+    if (mapped_abs_value < 0 ||
+        (mapped_abs_value == 0.0 && old_value < abs_info.flat)) {
+      mapped_code = WG_BUTTON_DPAD_UP;
+    } else {
+      mapped_code = WG_BUTTON_DPAD_DOWN;
+    }
+  }
+  OnButtonChange(mapped_code, mapped_abs_value,
+                 TimeTicksFromInputEvent(evdev_ev));
+}
+
+void GamepadEventConverterEvdev::ResetGamepad() {
+  base::TimeTicks timestamp = ui::EventTimeForNow();
+  for (int btn_code = 0; btn_code < WG_BUTTON_COUNT; ++btn_code) {
+    OnButtonChange(btn_code, 0, timestamp);
+  }
+
+  for (int abs_code = 0; abs_code < WG_ABS_COUNT; ++abs_code) {
+    OnAbsChange(abs_code, 0, timestamp);
+  }
+  OnSync(timestamp);
+}
+
+void GamepadEventConverterEvdev::ResyncGamepad() {

[spang, 2017/05/03 22:00:37]

Please either sync buttons or release them (or you might get a stuck button).

[jkwang, 2017/05/05 00:07:45]

Done.

+  EventDeviceInfo info;
+  if (!info.Initialize(fd_, path_)) {
+    LOG(ERROR) << "Failed to synchronize state for gamepad device: "
+               << path_.value();
+    Stop();
+    return;
+  }
+  for (int code = 0; code < ABS_CNT; ++code) {
+    abs_info_[code] = info.GetAbsInfoByCode(code);
+    if (info.HasAbsEvent(code) &&
+        abs_info_[code].value != info.GetAbsValue(code)) {
+      input_event event;
+      event.time = base::Time::UnixEpoch().ToTimeVal();

[spang, 2017/05/03 22:00:38]

Unix epoch is for the real time clock. Input uses the monotonic clock. Also, the
fact that timestamps of events from the same device are monotonically increasing
can be important.

Use base::TimeTicks::Now().

Please call it once (not in the loop).

[jkwang, 2017/05/05 00:07:45]

Done.

+      event.type = EV_ABS;
+      event.code = code;
+      event.value = info.GetAbsValue(code);
+      ProcessEvent(event);
+    }
+  }
+  OnSync(ui::EventTimeForNow());
+}
+
+void GamepadEventConverterEvdev::OnButtonChange(
+    unsigned int code,
+    double value,
+    const base::TimeTicks& timestamp) {
+  GamepadEvent event(input_device_.id, GamepadEventType::BUTTON, code, value,
+                     timestamp);
+  dispatcher_->DispatchGamepadEvent(event);
+  will_send_frame_ = true;
+}
+
+void GamepadEventConverterEvdev::OnAbsChange(unsigned int code,
+                                             double value,
+                                             const base::TimeTicks& timestamp) {
+  GamepadEvent event(input_device_.id, GamepadEventType::AXIS, code, value,
+                     timestamp);
+  dispatcher_->DispatchGamepadEvent(event);
+  will_send_frame_ = true;
+}
+
+void GamepadEventConverterEvdev::OnSync(const base::TimeTicks& timestamp) {
+  if (will_send_frame_) {
+    GamepadEvent event(input_device_.id, GamepadEventType::FRAME, 0, 0,
+                       timestamp);
+    dispatcher_->DispatchGamepadEvent(event);
+    will_send_frame_ = false;
+  }
+}
+}  //  namespace ui