commit 3204512f58a1
Author: Greg V <greg@unrelenting.technology>
Date:   Sun Dec 6 22:07:00 2020 +0000

    Bug 1680982 - Use evdev instead of the Linux legacy joystick API for gamepads
    
    Using evdev is a prerequisite for adding rumble (haptic feedback) and LED support.
    
    - BTN_GAMEPAD semantic buttons are interpreted directly,
    since all kernel drivers are supposed to use them correctly:
    https://www.kernel.org/doc/html/latest/input/gamepad.html
    - BTN_JOYSTICK legacy style numbered buttons use the model specific remappers
    - we support even strange devices that combine both styles in one device
    - the Linux gamepad module is enabled on FreeBSD and DragonFly, because
    these kernels provide evdev, and libudev-devd provides enough of libudev
    (evdev headers are provided by the devel/evdev-proto package)
    
    Differential Revision: https://phabricator.services.mozilla.com/D98868
---
 dom/gamepad/linux/LinuxGamepad.cpp | 262 ++++++++++++++++++++++++++++++++-----
 dom/gamepad/moz.build              |   2 +-
 2 files changed, 229 insertions(+), 35 deletions(-)

diff --git dom/gamepad/linux/LinuxGamepad.cpp dom/gamepad/linux/LinuxGamepad.cpp
index deee47b9d267..31f0aad7ae4a 100644
--- dom/gamepad/linux/LinuxGamepad.cpp
+++ dom/gamepad/linux/LinuxGamepad.cpp
@@ -5,15 +5,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /*
- * LinuxGamepadService: A Linux backend for the GamepadService.
- * Derived from the kernel documentation at
- * http://www.kernel.org/doc/Documentation/input/joystick-api.txt
+ * LinuxGamepadService: An evdev backend for the GamepadService.
+ *
+ * Ref: https://www.kernel.org/doc/html/latest/input/gamepad.html
  */
 #include <algorithm>
+#include <unordered_map>
 #include <cstddef>
 
 #include <glib.h>
-#include <linux/joystick.h>
+#include <linux/input.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <sys/ioctl.h>
@@ -21,10 +22,14 @@
 #include "nscore.h"
 #include "mozilla/dom/GamepadHandle.h"
 #include "mozilla/dom/GamepadPlatformService.h"
+#include "mozilla/dom/GamepadRemapping.h"
 #include "mozilla/Tainting.h"
 #include "mozilla/UniquePtr.h"
 #include "udev.h"
 
+#define LONG_BITS (sizeof(long) * 8)
+#define NLONGS(x) (((x) + LONG_BITS - 1) / LONG_BITS)
+
 namespace {
 
 using namespace mozilla::dom;
@@ -36,19 +41,29 @@ using mozilla::udev_list_entry;
 using mozilla::udev_monitor;
 using mozilla::UniquePtr;
 
-static const float kMaxAxisValue = 32767.0;
-static const char kJoystickPath[] = "/dev/input/js";
+static const char kEvdevPath[] = "/dev/input/event";
+
+static inline bool TestBit(const unsigned long* arr, int bit) {
+  return !!(arr[bit / LONG_BITS] & (1LL << (bit % LONG_BITS)));
+}
+
+static inline double ScaleAxis(const input_absinfo& info, int value) {
+  return 2.0 * (value - info.minimum) / (double)(info.maximum - info.minimum) -
+         1.0;
+}
 
 // TODO: should find a USB identifier for each device so we can
 // provide something that persists across connect/disconnect cycles.
-typedef struct {
+struct Gamepad {
   GamepadHandle handle;
-  guint source_id;
-  int numAxes;
-  int numButtons;
-  char idstring[256];
-  char devpath[PATH_MAX];
-} Gamepad;
+  RefPtr<GamepadRemapper> remapper = nullptr;
+  guint source_id = UINT_MAX;
+  char idstring[256] = {0};
+  char devpath[PATH_MAX] = {0};
+  uint8_t key_map[KEY_MAX] = {0};
+  uint8_t abs_map[ABS_MAX] = {0};
+  std::unordered_map<uint16_t, input_absinfo> abs_info;
+};
 
 class LinuxGamepadService {
  public:
@@ -66,7 +81,7 @@ class LinuxGamepadService {
   bool is_gamepad(struct udev_device* dev);
   void ReadUdevChange();
 
-  // handler for data from /dev/input/jsN
+  // handler for data from /dev/input/eventN
   static gboolean OnGamepadData(GIOChannel* source, GIOCondition condition,
                                 gpointer data);
 
@@ -114,8 +129,14 @@ void LinuxGamepadService::AddDevice(struct udev_device* dev) {
   g_io_channel_set_encoding(channel, nullptr, nullptr);
   g_io_channel_set_buffered(channel, FALSE);
   int fd = g_io_channel_unix_get_fd(channel);
+
+  struct input_id id {};
+  if (ioctl(fd, EVIOCGID, &id) == -1) {
+    return;
+  }
+
   char name[128];
-  if (ioctl(fd, JSIOCGNAME(sizeof(name)), &name) == -1) {
+  if (ioctl(fd, EVIOCGNAME(sizeof(name)), &name) == -1) {
     strcpy(name, "unknown");
   }
   const char* vendor_id =
@@ -131,20 +152,86 @@ void LinuxGamepadService::AddDevice(struct udev_device* dev) {
       model_id = mUdev.udev_device_get_sysattr_value(parent, "id/product");
     }
   }
+  if (!vendor_id && id.vendor != 0) {
+    vendor_id = (const char*)alloca(5);
+    snprintf((char*)vendor_id, 5, "%04x", id.vendor);
+  }
+  if (!model_id && id.product != 0) {
+    model_id = (const char*)alloca(5);
+    snprintf((char*)model_id, 5, "%04x", id.product);
+  }
   snprintf(gamepad->idstring, sizeof(gamepad->idstring), "%s-%s-%s",
            vendor_id ? vendor_id : "unknown", model_id ? model_id : "unknown",
            name);
 
   char numAxes = 0, numButtons = 0;
-  ioctl(fd, JSIOCGAXES, &numAxes);
-  gamepad->numAxes = numAxes;
-  ioctl(fd, JSIOCGBUTTONS, &numButtons);
-  gamepad->numButtons = numButtons;
+  unsigned long key_bits[NLONGS(KEY_CNT)] = {0};
+  unsigned long abs_bits[NLONGS(ABS_CNT)] = {0};
+  ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(key_bits)), key_bits);
+  ioctl(fd, EVIOCGBIT(EV_ABS, sizeof(abs_bits)), abs_bits);
+
+  /* Here, we try to support even strange cases where proper semantic
+   * BTN_GAMEPAD button are combined with arbitrary extra buttons. */
+  for (uint16_t i = BTN_JOYSTICK; i < KEY_MAX; i++) {
+    /* Do not map semantic buttons, they are handled directly */
+    if (i == BTN_GAMEPAD) {
+      i = BTN_THUMBR + 1;
+      continue;
+    }
+    if (i == BTN_DPAD_UP) {
+      i = BTN_DPAD_RIGHT + 1;
+      continue;
+    }
+    if (TestBit(key_bits, i)) {
+      gamepad->key_map[i] = numButtons++;
+    }
+  }
+  for (uint16_t i = 0; i < BTN_JOYSTICK; i++) {
+    if (TestBit(key_bits, i)) {
+      gamepad->key_map[i] = numButtons++;
+    }
+  }
+  for (uint16_t i = BTN_GAMEPAD; i <= BTN_THUMBR; i++) {
+    /* But if any semantic event exists, count them all */
+    if (TestBit(key_bits, i)) {
+      numButtons += BUTTON_INDEX_COUNT;
+      break;
+    }
+  }
+  for (uint16_t i = 0; i < ABS_MAX; ++i) {
+    if (TestBit(abs_bits, i)) {
+      gamepad->abs_info.emplace(i, input_absinfo{});
+      if (ioctl(fd, EVIOCGABS(i), &gamepad->abs_info[i]) < 0) {
+        continue;
+      }
+      if (gamepad->abs_info[i].minimum == gamepad->abs_info[i].maximum) {
+        gamepad->abs_info.erase(i);
+        continue;
+      }
+      gamepad->abs_map[i] = numAxes++;
+    }
+  }
+
+  if (numAxes == 0) {
+    NS_WARNING("Gamepad with zero axes detected?");
+  }
+  if (numButtons == 0) {
+    NS_WARNING("Gamepad with zero buttons detected?");
+  }
+
+  bool defaultRemapper = false;
+  RefPtr<GamepadRemapper> remapper =
+      GetGamepadRemapper(id.vendor, id.product, defaultRemapper);
+  MOZ_ASSERT(remapper);
+  remapper->SetAxisCount(numAxes);
+  remapper->SetButtonCount(numButtons);
 
   gamepad->handle = service->AddGamepad(
-      gamepad->idstring, mozilla::dom::GamepadMappingType::_empty,
-      mozilla::dom::GamepadHand::_empty, gamepad->numButtons, gamepad->numAxes,
-      0, 0, 0);  // TODO: Bug 680289, implement gamepad haptics for Linux.
+      gamepad->idstring, remapper->GetMappingType(), GamepadHand::_empty,
+      remapper->GetButtonCount(), remapper->GetAxisCount(), 0,
+      remapper->GetLightIndicatorCount(), remapper->GetTouchEventCount());
+  gamepad->remapper = remapper.forget();
+  // TODO: Bug 680289, implement gamepad haptics for Linux.
   // TODO: Bug 1523355, implement gamepad lighindicator and touch for Linux.
 
   gamepad->source_id =
@@ -257,7 +344,7 @@ bool LinuxGamepadService::is_gamepad(struct udev_device* dev) {
   if (!devpath) {
     return false;
   }
-  if (strncmp(kJoystickPath, devpath, sizeof(kJoystickPath) - 1) != 0) {
+  if (strncmp(kEvdevPath, devpath, sizeof(kEvdevPath) - 1) != 0) {
     return false;
   }
 
@@ -292,7 +379,7 @@ gboolean LinuxGamepadService::OnGamepadData(GIOChannel* source,
   if (condition & G_IO_ERR || condition & G_IO_HUP) return FALSE;
 
   while (true) {
-    struct js_event event;
+    struct input_event event {};
     gsize count;
     GError* err = nullptr;
     if (g_io_channel_read_chars(source, (gchar*)&event, sizeof(event), &count,
@@ -301,18 +388,125 @@ gboolean LinuxGamepadService::OnGamepadData(GIOChannel* source,
       break;
     }
 
-    // TODO: store device state?
-    if (event.type & JS_EVENT_INIT) {
-      continue;
-    }
-
     switch (event.type) {
-      case JS_EVENT_BUTTON:
-        service->NewButtonEvent(gamepad->handle, event.number, !!event.value);
+      case EV_KEY:
+        switch (event.code) {
+          /* The gamepad events are meaningful, and according to
+           * https://www.kernel.org/doc/html/latest/input/gamepad.html
+           * "No other devices, that do not look/feel like a gamepad, shall
+           * report these events" */
+          case BTN_SOUTH:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_PRIMARY,
+                                    !!event.value);
+            break;
+          case BTN_EAST:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_SECONDARY,
+                                    !!event.value);
+            break;
+          case BTN_NORTH:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_QUATERNARY,
+                                    !!event.value);
+            break;
+          case BTN_WEST:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_TERTIARY,
+                                    !!event.value);
+            break;
+          case BTN_TL:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_LEFT_SHOULDER,
+                                    !!event.value);
+            break;
+          case BTN_TR:
+            service->NewButtonEvent(gamepad->handle,
+                                    BUTTON_INDEX_RIGHT_SHOULDER, !!event.value);
+            break;
+          case BTN_TL2:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_LEFT_TRIGGER,
+                                    !!event.value);
+            break;
+          case BTN_TR2:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_RIGHT_TRIGGER,
+                                    !!event.value);
+            break;
+          case BTN_SELECT:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_BACK_SELECT,
+                                    !!event.value);
+            break;
+          case BTN_START:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_START,
+                                    !!event.value);
+            break;
+          case BTN_MODE:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_META,
+                                    !!event.value);
+            break;
+          case BTN_THUMBL:
+            service->NewButtonEvent(
+                gamepad->handle, BUTTON_INDEX_LEFT_THUMBSTICK, !!event.value);
+            break;
+          case BTN_THUMBR:
+            service->NewButtonEvent(
+                gamepad->handle, BUTTON_INDEX_RIGHT_THUMBSTICK, !!event.value);
+            break;
+          case BTN_DPAD_UP:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_DPAD_UP,
+                                    !!event.value);
+            break;
+          case BTN_DPAD_DOWN:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_DPAD_DOWN,
+                                    !!event.value);
+            break;
+          case BTN_DPAD_LEFT:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_DPAD_LEFT,
+                                    !!event.value);
+            break;
+          case BTN_DPAD_RIGHT:
+            service->NewButtonEvent(gamepad->handle, BUTTON_INDEX_DPAD_RIGHT,
+                                    !!event.value);
+            break;
+          default:
+            /* For non-gamepad events, this is the "anything goes" numbered
+             * handling that should be handled with remappers. */
+            gamepad->remapper->RemapButtonEvent(
+                gamepad->handle, gamepad->key_map[event.code], !!event.value);
+            break;
+        }
         break;
-      case JS_EVENT_AXIS:
-        service->NewAxisMoveEvent(gamepad->handle, event.number,
-                                  ((float)event.value) / kMaxAxisValue);
+      case EV_ABS:
+        if (!gamepad->abs_info.count(event.code)) continue;
+        switch (event.code) {
+          case ABS_HAT0X:
+            service->NewButtonEvent(
+                gamepad->handle, BUTTON_INDEX_DPAD_LEFT,
+                AxisNegativeAsButton(
+                    ScaleAxis(gamepad->abs_info[event.code], event.value)));
+            service->NewButtonEvent(
+                gamepad->handle, BUTTON_INDEX_DPAD_RIGHT,
+                AxisPositiveAsButton(
+                    ScaleAxis(gamepad->abs_info[event.code], event.value)));
+            break;
+          case ABS_HAT0Y:
+            service->NewButtonEvent(
+                gamepad->handle, BUTTON_INDEX_DPAD_UP,
+                AxisNegativeAsButton(
+                    ScaleAxis(gamepad->abs_info[event.code], event.value)));
+            service->NewButtonEvent(
+                gamepad->handle, BUTTON_INDEX_DPAD_DOWN,
+                AxisPositiveAsButton(
+                    ScaleAxis(gamepad->abs_info[event.code], event.value)));
+            break;
+          case ABS_HAT1X:
+          case ABS_HAT1Y:
+          case ABS_HAT2X:
+          case ABS_HAT2Y:
+          case ABS_HAT3X:
+          case ABS_HAT3Y:
+            break;
+          default:
+            gamepad->remapper->RemapAxisMoveEvent(
+                gamepad->handle, gamepad->abs_map[event.code],
+                ScaleAxis(gamepad->abs_info[event.code], event.value));
+            break;
+        }
         break;
     }
   }
diff --git dom/gamepad/moz.build dom/gamepad/moz.build
index 5f55d5a95e96..544b7f927736 100644
--- dom/gamepad/moz.build
+++ dom/gamepad/moz.build
@@ -59,7 +59,7 @@ elif CONFIG["MOZ_WIDGET_TOOLKIT"] == "windows":
     UNIFIED_SOURCES += ["windows/WindowsGamepad.cpp"]
 elif CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
     UNIFIED_SOURCES += ["android/AndroidGamepad.cpp"]
-elif CONFIG["OS_ARCH"] == "Linux":
+elif CONFIG["OS_ARCH"] in ("Linux", "FreeBSD", "DragonFly"):
     UNIFIED_SOURCES += ["linux/LinuxGamepad.cpp"]
 else:
     UNIFIED_SOURCES += ["fallback/FallbackGamepad.cpp"]