About

This patch changes Linux's joydev module in order to make certain PlayStation dance pads, coupled with certain PlayStation/USB adapters, work with StepMania, fixing the infamous axis problem. I know for sure that it works with my dance pad and my adapter (model Pu120T) in the Linux versions listed below. Two dance pads are supported simultaneously.

Download

Download the file that best matches your kernel version, but notice that version 1.1 of the patch applies the fix to whatever device Linux recognizes as a joystick, whereas version 1.2 applies the fix selectively.

Use

1. Apply this patch to a properly configured Linux source tree:

patch -Np1 -i joydev-dancepad.patch

2. Edit drivers/input/joydev.c so that the macros DANCEPAD_VENDOR and DANCEPAD_PRODUCT correspond to your adapter. You can find which values to use with, e.g., lsusb.
3. Compile and install joydev.ko.
4. When using the module, make sure StepMania is reading from /dev/input/js*, and not /dev/input/event*. You could remove the latter in order to make sure it will read from the correct device.

If the steps above sound difficult, you may want to read the answers to this question. Some tools that may come in handy are dmesg and lsof.

Applying this patch to your kernel for geeks / non-kernel developers.

Here is the workings of how to apply this patch to your kernel. Separate instructions are provided for Mageia 5, Arch Linux and Raspbian (Raspberry Pi). If you're using other Linux distribution you may need to adjust them slightly.

Prep

You will need at least: patch, wget, gcc and make installed, along with enough space for ther kernel source that matches your distribution. This does expect you to be comfortable with the command line.

Backup existing module

cd /lib/modules/`uname -r`/kernel/drivers/input/
cp joydev.ko.xz joydev.ko.xz.orig

Mageia 5

Unpack and CD into to the kernel source tree

Get your running kernel version, by running uname -r

Install matching source, in my case 4.4.92-1.mga5

 urpmi kernel-source-4.4.92-1.mga5 patch gcc wget make
 cd /usr/src/kernel-4.4.92-1.mga5
 ls -l drivers/input/joydev.c && echo "Yes, this is the correct place and the source file is present."

Get the patch

 wget https://raw.githubusercontent.com/adiel-mittmann/dancepad/master/joydev-dancepad-1.2-4.13.3.patch

Apply patch

patch -Np1 -i joydev-dancepad-1.2-4.13.3.patch

Output should be like:

 patching file drivers/input/joydev.c
 Hunk #1 succeeded at 38 (offset 1 line).
 Hunk #2 succeeded at 61 (offset 1 line).
 Hunk #3 succeeded at 121 (offset 1 line).
 Hunk #4 succeeded at 1008 (offset -5 lines).

Prepare the source tree to compile modules for your existing running kernel

make mrproper
cp /usr/lib/modules/$(uname -r)/build/.config ./
cp /usr/lib/modules/$(uname -r)/build/Module.symvers ./
make oldconfig
make prepare && make scripts

Build the input modules

make SUBDIRS=drivers/input modules

Check output from the build

ls drivers/input/joydev.ko -l
xz drivers/input/joydev.ko

Install module

unplug the dance pad, if you have it plugged in, then:

rmmod joydev
cp drivers/input/joydev.ko.xz /lib/modules/`uname -r`/kernel/drivers/input/
depmod
modprobe joykey
dmesg
lsmod | grep joydev
rmmod joydev

Arch Linux

All commands listed below are run under your regular non-root user. Sudo is used for commands that need root access.

Make sure kernel headers are installed

Prepare build environment

mkdir joydev
cd joydev

cat > Makefile <<"HERE"
obj-m = joydev.o
KVERSION = $(shell uname -r)

all:
	make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
	make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean
HERE

# get the latest joydev source code.
# if you need a specific version - you can use any tag listed at https://github.com/torvalds/linux/tags
# instead of HEAD
wget -q https://raw.githubusercontent.com/torvalds/linux/HEAD/drivers/input/joydev.c

# get the patch
wget -q https://raw.githubusercontent.com/adiel-mittmann/dancepad/master/joydev-dancepad-1.2-4.13.3.patch

# patch the source
patch -Np3 -i joydev-dancepad-1.2-4.13.3.patch

# edit joydev.c changing DANCEPAD_VENDOR and/or DANCEPAD_PRODUCT if necessary

Build the module

Install the module

First unplug the dance pad.

sudo modprobe -r joydev
sudo cp joydev.ko.xz /lib/modules/`uname -r`/kernel/drivers/input/
sudo depmod
sudo modprobe joydev

Raspbian

Make sure kernel headers are installed

apt install raspberrypi-kernel-headers

Next steps

Follow Arch Linux instructions.

Connect the dance pad

Check the kernel logs by running: dmesg

The output should show something like the example below. The "Dancepad detected: activating workaround" entries are important.

[14293.162094] usb 4-1.1: new low-speed USB device number 3 using ehci-pci
[14293.253453] usb 4-1.1: New USB device found, idVendor=0810, idProduct=0001
[14293.253459] usb 4-1.1: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[14293.253469] usb 4-1.1: Product: Twin USB Joystick
[14293.269226] input: Twin USB Joystick as /devices/pci0000:00/0000:00:1d.0/usb4/4-1/4-1.1/4-1.1:1.0/0003:0810:0001.000B/input/input24
[14293.269305] input: Twin USB Joystick as /devices/pci0000:00/0000:00:1d.0/usb4/4-1/4-1.1/4-1.1:1.0/0003:0810:0001.000B/input/input25
[14293.269369] pantherlord 0003:0810:0001.000B: input,hidraw10: USB HID v1.10 Joystick [Twin USB Joystick] on usb-0000:00:1d.0-1.1/input0
[14293.269376] pantherlord 0003:0810:0001.000B: Force feedback for PantherLord/GreenAsia devices by Anssi Hannula <anssi.hannula@gmail.com>
[14293.276830] Dancepad detected: activating workaround.
[14293.320238] Dancepad detected: activating workaround.

Remove /dev/input/eventXY before running stepmania

You'll need to do this everytime you reconnect the dance pad and/or reboot your computer.

sudo rm $(readlink -f $(evdev-joystick --l))

If you're looking for a permanent solution you could try to add this udev rule into /usr/lib/udev/rules.d/99-remove_event_device_for_patched_joydev_device.rules:

# remove /dev/input/event device corresponding to an axis-issue affected dance pad
# adjust idVendor and idProduct variables based on the output of lsusb command (while dance pad is connected)
KERNEL=="event*", NAME="input/%k", ATTRS{idVendor}=="0810", ATTRS{idProduct}=="0001", ACTION=="add", RUN+="/usr/bin/rm /dev/input/%k"

DKMS configuration

Experimental DKMS setup is located in dkms/. In order to use it copy joydev_dance-1.0 directory into /usr/src (edit VENDOR and PRODUCT in joydev_dance.c if appropriate) and run dkms install joydev_dance/1.0. This should compile and install joydev_dance module which can live next to the official joydev module. Also DKMS framework should take care of recompiling this module everytime you change (e. g. upgrade) your kernel which means you have one less thing to worry about.

Beware that you have to blacklist joydev module so that only the patched one is loaded (otherwise you'll end up with two gamepads detected).

echo "blacklist joydev" > /etc/modprobe.d/joydev.conf 

Thanks

I would like to thank Jozef Riha for his help in testing version 1.2 of the patch.