Adding a kernel task, as the /dev/input/js0 is created by the kernel driver (usbhid) itself. udev does not create device nodes, it just adds additional properties, runs extra programs on the device nodes, etc.
So cases a/ vs. b/ is interesting -- in both cases you get three HID devices, just that in the wireless USB dongle case the "hid-generic" driver grabs them as it just sees the transceiver, while in the wired USB case it's the "logitech" driver as it sees the devices directly. input_id only actually sees a joystick with the wireless transceiver (see a1), there you see that the js0 device claims to have tons of absolute axes: capabilities/abs decoded bit map: bit 0: FFFFFF01000701FF while in the b/ case capabilities/abs is zero, i. e. no axes. input_id is here: https://github.com/systemd/systemd/blob/master/src/udev/udev-builtin- input_id.c In test_pointers() you see that has_joystick_axes_or_buttons is determined by buttons/axes which are typical for a joystick: /* joysticks don't necessarily have buttons; e. g. * rudders/pedals are joystick-like, but buttonless; they have * other fancy axes */ has_joystick_axes_or_buttons = test_bit(BTN_TRIGGER, bitmask_key) || test_bit(BTN_A, bitmask_key) || test_bit(BTN_1, bitmask_key) || test_bit(ABS_RX, bitmask_abs) || test_bit(ABS_RY, bitmask_abs) || test_bit(ABS_RZ, bitmask_abs) || test_bit(ABS_THROTTLE, bitmask_abs) || test_bit(ABS_RUDDER, bitmask_abs) || test_bit(ABS_WHEEL, bitmask_abs) || test_bit(ABS_GAS, bitmask_abs) || test_bit(ABS_BRAKE, bitmask_abs); This needs to be checked against the decoded capabilities/key (for the buttons) and capabilities/abs (for the absolute axes), the numerical values of the evdev constants are in /usr/include/linux/input.h. The above is just a heuristic of course which has been refined over time, and might need more refinement. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1458631 Title: udev: /dev/input/js0 is created but no joystick attached Status in linux package in Ubuntu: Incomplete Status in systemd package in Ubuntu: Incomplete Bug description: With ubuntu vivid i see a /dev/input/js0. I do not have a joystick or gamepad attached. This invalid input device cause a game in steam "Crypt of the necrodancer" to crash during start. The game works fine when I delete it. This appears to be a ubuntu specific bug as it does not show up on fedora 22. It goes away if I unplug the mouse/keyboard usb dongle I use. If I attach a wired keyboard only it does not show up. I tried adding a wired mouse too, but that causes js0 to appear too. The output of udevadm changes depending on what mouse I have attached. The following output is from using the dongle for my wireless mouse/keyboard (both microsoft products) $sudo udevadm info /dev/input/js0 P: /devices/pci0000:00/0000:00:1a.2/usb5/5-1/5-1:1.2/0003:045E:0745.0003/input/input7/js0 N: input/js0 S: input/by-id/usb-Microsoft_Microsoft®_2.4GHz_Transceiver_v6.0-if02-joystick S: input/by-path/pci-0000:00:1a.2-usb-0:1:1.2-joystick E: DEVLINKS=/dev/input/by-id/usb-Microsoft_Microsoft®_2.4GHz_Transceiver_v6.0-if02-joystick /dev/input/by-path/pci-0000:00:1a.2-usb-0:1:1.2-joystick E: DEVNAME=/dev/input/js0 E: DEVPATH=/devices/pci0000:00/0000:00:1a.2/usb5/5-1/5-1:1.2/0003:045E:0745.0003/input/input7/js0 E: ID_BUS=usb E: ID_FOR_SEAT=input-pci-0000_00_1a_2-usb-0_1_1_2 E: ID_INPUT=1 E: ID_INPUT_JOYSTICK=1 E: ID_INPUT_KEY=1 E: ID_INPUT_KEYBOARD=1 E: ID_MODEL=Microsoft®_2.4GHz_Transceiver_v6.0 E: ID_MODEL_ENC=Microsoft®\x202.4GHz\x20Transceiver\x20v6.0 E: ID_MODEL_ID=0745 E: ID_PATH=pci-0000:00:1a.2-usb-0:1:1.2 E: ID_PATH_TAG=pci-0000_00_1a_2-usb-0_1_1_2 E: ID_REVISION=0251 E: ID_SERIAL=Microsoft_Microsoft®_2.4GHz_Transceiver_v6.0 E: ID_TYPE=hid E: ID_USB_DRIVER=usbhid E: ID_USB_INTERFACES=:030101:030102:030000: E: ID_USB_INTERFACE_NUM=02 E: ID_VENDOR=Microsoft E: ID_VENDOR_ENC=Microsoft E: ID_VENDOR_ID=045e E: MAJOR=13 E: MINOR=0 E: SUBSYSTEM=input E: TAGS=:seat:uaccess: E: USEC_INITIALIZED=117298 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1458631/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
