steelseries udev rules+script

98-steelseries.rules

ACTION=="add", SUBSYSTEM=="hidraw", ATTRS{idVendor}=="1038" RUN+="/etc/udev/rules.d/steelseries-perms.py '%E{DEVNAME}'"

steelseries-perms.py

#!/usr/bin/env python3

import ctypes
import fcntl
import os
import struct
import sys

# from linux headers hidraw.h, hid.h, and ioctl.h
_IOC_NRBITS = 8
_IOC_TYPEBITS = 8
_IOC_SIZEBITS = 14

_IOC_NRSHIFT = 0
_IOC_TYPESHIFT = _IOC_NRSHIFT + _IOC_NRBITS
_IOC_SIZESHIFT = _IOC_TYPESHIFT + _IOC_TYPEBITS
_IOC_DIRSHIFT = _IOC_SIZESHIFT + _IOC_SIZEBITS

_IOC_READ = 2

def _IOC(dir, type, nr, size):
	return (dir << _IOC_DIRSHIFT) | \
		(ord(type) << _IOC_TYPESHIFT) | \
		(nr << _IOC_NRSHIFT) | \
		(size << _IOC_SIZESHIFT)

def _IOR(type, nr, size):
	return _IOC(_IOC_READ, type, nr, size)

HID_MAX_DESCRIPTOR_SIZE = 4096

class hidraw_report_descriptor(ctypes.Structure):
	_fields_ = [
		('size', ctypes.c_uint),
		('value', ctypes.c_uint8 * HID_MAX_DESCRIPTOR_SIZE),
	]

HIDIOCGRDESCSIZE = _IOR('H', 0x01, ctypes.sizeof(ctypes.c_int))
HIDIOCGRDESC = _IOR('H', 0x02, ctypes.sizeof(hidraw_report_descriptor))

hidraw = sys.argv[1]

with open(hidraw, 'wb') as fd:
	size = ctypes.c_uint()
	fcntl.ioctl(fd, HIDIOCGRDESCSIZE, size, True)
	descriptor = hidraw_report_descriptor()
	descriptor.size = size
	fcntl.ioctl(fd, HIDIOCGRDESC, descriptor, True)

descriptor = bytes(descriptor.value)[0:int.from_bytes(size, byteorder=sys.byteorder)]

# walk through the descriptor until we find the usage page
usagePage = 0
i = 0
while i < len(descriptor):
	b = descriptor[i]
	bTag = (b >> 4) & 0x0F
	bType = (b >> 2) & 0x03
	bSize = b & 0x03

	if bSize != 0:
		bSize = 2 ** (bSize - 1)

	if b == 0b11111110:
		# long types shouldn't be the usage page, skip them
		i += 3 + descriptor[i+1]
		continue

	if bType == 1 and bTag == 0:
		# usage page, grab it
		format = ''
		if bSize == 1:
			format = 'B'
		elif bSize == 2:
			format = 'H'
		elif bSize == 4:
			format = 'I'
		else:
			raise Exception('usage page is length {}???'.format(bSize))
		usagePage = struct.unpack_from(format, descriptor, i + 1)[0]
		break

	i += 1 + bSize

# set read/write permissions for vendor and consumer usage pages
# some devices don't use the vendor page, allow the interfaces they do use
if usagePage == 0x000C or usagePage >= 0xFF00:
	os.chmod(hidraw, 0o666)