Solaar/lib/logitech_receiver/settings.py

782 lines
32 KiB
Python

# -*- python-mode -*-
# -*- coding: UTF-8 -*-
## Copyright (C) 2012-2013 Daniel Pavel
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License along
## with this program; if not, write to the Free Software Foundation, Inc.,
## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
from __future__ import absolute_import, division, print_function, unicode_literals
import math
from copy import copy as _copy
from logging import DEBUG as _DEBUG
from logging import getLogger
from .common import NamedInt as _NamedInt
from .common import NamedInts as _NamedInts
from .common import bytes2int as _bytes2int
from .common import int2bytes as _int2bytes
_log = getLogger(__name__)
del getLogger
#
#
#
KIND = _NamedInts(toggle=0x01, choice=0x02, range=0x04, map_choice=0x0A, multiple_toggle=0x10)
class Setting(object):
"""A setting descriptor.
Needs to be instantiated for each specific device."""
__slots__ = (
'name', 'label', 'description', 'kind', 'device_kind', 'feature', 'persist', '_rw', '_validator', '_callback',
'_device', '_value'
)
def __init__(self, name, rw, validator=None, callback=None, kind=None, device_kind=None, feature=None, persist=True):
assert name
self.name = name[0]
self.label = name[1]
self.description = name[2]
self.device_kind = device_kind
self.feature = getattr(rw, 'feature', None)
self.persist = persist
self._rw = rw
assert (validator and not callback) or (not validator and callback)
self._validator = validator
self._callback = callback
assert kind is None or validator is None or kind & validator.kind != 0
self.kind = kind or getattr(validator, 'kind', None)
def __call__(self, device):
assert not hasattr(self, '_value')
# combined keyboards and touchpads (e.g., K400) break this assertion so don't use it
# assert self.device_kind is None or device.kind in self.device_kind
p = device.protocol
if p == 1.0:
# HID++ 1.0 devices do not support features
assert self._rw.kind == RegisterRW.kind
elif p >= 2.0:
# HID++ 2.0 devices do not support registers
assert self._rw.kind == FeatureRW.kind
o = _copy(self)
if o._callback:
o._validator = o._callback(device)
if o._validator is None:
return None
assert o.kind is None or o.kind & o._validator.kind != 0
o.kind = o.kind or o._validator.kind
o._value = None
o._device = device
return o
@property
def choices(self):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
return self._validator.choices if self._validator and self._validator.kind & KIND.choice else None
@property
def range(self):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
if self._validator.kind == KIND.range:
return (self._validator.min_value, self._validator.max_value)
def read(self, cached=True):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings read %r from %s', self.name, self._value, self._device)
if self.persist and self._value is None and self._device.persister:
# We haven't read a value from the device yet,
# maybe we have something in the configuration.
self._value = self._device.persister.get(self.name)
if cached and self._value is not None:
if self.persist and self._device.persister and self.name not in self._device.persister:
# If this is a new device (or a new setting for an old device),
# make sure to save its current value for the next time.
self._device.persister[self.name] = self._value
return self._value
if self._device.online:
reply = self._rw.read(self._device)
if reply:
self._value = self._validator.validate_read(reply)
if self.persist and self._device.persister and self.name not in self._device.persister:
# Don't update the persister if it already has a value,
# otherwise the first read might overwrite the value we wanted.
self._device.persister[self.name] = self._value
return self._value
def write(self, value):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert value is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings write %r to %s', self.name, value, self._device)
if self._device.online:
# Remember the value we're trying to set, even if the write fails.
# This way even if the device is offline or some other error occurs,
# the last value we've tried to write is remembered in the configuration.
self._value = value
if self.persist and self._device.persister:
self._device.persister[self.name] = value
current_value = None
if self._validator.needs_current_value:
# the validator needs the current value, possibly to merge flag values
current_value = self._rw.read(self._device)
data_bytes = self._validator.prepare_write(value, current_value)
if data_bytes is not None:
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings prepare write(%s) => %r', self.name, value, data_bytes)
reply = self._rw.write(self._device, data_bytes)
if not reply:
# tell whomever is calling that the write failed
return None
return value
def apply(self):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: apply %s (%s)', self.name, self._value, self._device)
value = self.read(self.persist) # Don't use persisted value if setting doesn't persist
if self.persist and value is not None: # If setting doesn't persist no need to write value just read
self.write(value)
def __str__(self):
if hasattr(self, '_value'):
assert hasattr(self, '_device')
return '<Setting([%s:%s] %s:%s=%s)>' % (
self._rw.kind, self._validator.kind if self._validator else None, self._device.codename, self.name, self._value
)
return '<Setting([%s:%s] %s)>' % (self._rw.kind, self._validator.kind if self._validator else None, self.name)
__unicode__ = __repr__ = __str__
class Settings(Setting):
"""A setting descriptor for multiple choices, being a map from keys to values.
Needs to be instantiated for each specific device."""
def read(self, cached=True):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings read %r from %s', self.name, self._value, self._device)
if self.persist and self._value is None and getattr(self._device, 'persister', None):
# We haven't read a value from the device yet,
# maybe we have something in the configuration.
self._value = self._device.persister.get(self.name)
if cached and self._value is not None:
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
# If this is a new device (or a new setting for an old device),
# make sure to save its current value for the next time.
self._device.persister[self.name] = self._value
return self._value
if self._device.online:
reply_map = {}
for key in self._validator.choices:
reply = self._rw.read(self._device, key)
if reply:
# keys are ints, because that is what the device uses,
# encoded into strings because JSON requires strings as keys
reply_map[str(int(key))] = self._validator.validate_read(reply, key)
self._value = reply_map
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
# Don't update the persister if it already has a value,
# otherwise the first read might overwrite the value we wanted.
self._device.persister[self.name] = self._value
return self._value
def read_key(self, key, cached=True):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert key is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings read %r key %r from %s', self.name, self._value, key, self._device)
if self._value is None and getattr(self._device, 'persister', None):
self._value = self._device.persister.get(self.name)
if cached and self._value is not None:
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
self._device.persister[self.name] = self._value
return self._value[str(int(key))]
if self._device.online:
reply = self._rw.read(self._device, key)
if reply:
self._value[str(int(key))] = self._validator.validate_read(reply, key)
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
self._device.persister[self.name] = self._value
return self._value[str(int(key))]
def write(self, map):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert map is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings write %r to %s', self.name, map, self._device)
if self._device.online:
# Remember the value we're trying to set, even if the write fails.
# This way even if the device is offline or some other error occurs,
# the last value we've tried to write is remembered in the configuration.
self._value = map
if self.persist and self._device.persister:
self._device.persister[self.name] = map
for key, value in map.items():
data_bytes = self._validator.prepare_write(int(key), value)
if data_bytes is not None:
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings prepare map write(%s,%s) => %r', self.name, key, value, data_bytes)
reply = self._rw.write(self._device, int(key), data_bytes)
if not reply:
return None
return map
def write_key_value(self, key, value):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert key is not None
assert value is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings write key %r value %r to %s', self.name, key, value, self._device)
if self._device.online:
# Remember the value we're trying to set, even if the write fails.
# This way even if the device is offline or some other error occurs,
# the last value we've tried to write is remembered in the configuration.
try:
data_bytes = self._validator.prepare_write(int(key), value)
self._value[str(key)] = value
if self.persist and self._device.persister:
self._device.persister[self.name] = self._value
except ValueError:
data_bytes = value = None
if data_bytes is not None:
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings prepare key value write(%s,%s) => %r', self.name, key, value, data_bytes)
reply = self._rw.write(self._device, int(key), data_bytes)
if not reply:
# tell whomever is calling that the write failed
return None
return value
class BitFieldSetting(Setting):
"""A setting descriptor for a set of choices represented by one bit each, being a map from options to booleans.
Needs to be instantiated for each specific device."""
def read(self, cached=True):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings read %r from %s', self.name, self._value, self._device)
if self._value is None and getattr(self._device, 'persister', None):
# We haven't read a value from the device yet,
# maybe we have something in the configuration.
self._value = self._device.persister.get(self.name)
if cached and self._value is not None:
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
# If this is a new device (or a new setting for an old device),
# make sure to save its current value for the next time.
self._device.persister[self.name] = self._value
return self._value
if self._device.online:
reply_map = {}
reply = self._rw.read(self._device)
if reply:
# keys are ints, because that is what the device uses,
# encoded into strings because JSON requires strings as keys
reply_map = self._validator.validate_read(reply)
self._value = reply_map
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
# Don't update the persister if it already has a value,
# otherwise the first read might overwrite the value we wanted.
self._device.persister[self.name] = self._value
return self._value
def read_key(self, key, cached=True):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert key is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings read %r key %r from %s', self.name, self._value, key, self._device)
if self._value is None and getattr(self._device, 'persister', None):
self._value = self._device.persister.get(self.name)
if cached and self._value is not None:
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
self._device.persister[self.name] = self._value
return self._value[str(int(key))]
if self._device.online:
reply = self._rw.read(self._device, key)
if reply:
self._value = self._validator.validate_read(reply)
if self.persist and getattr(self._device, 'persister', None) and self.name not in self._device.persister:
self._device.persister[self.name] = self._value
return self._value[str(int(key))]
def write(self, map):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert map is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings write %r to %s', self.name, map, self._device)
if self._device.online:
# Remember the value we're trying to set, even if the write fails.
# This way even if the device is offline or some other error occurs,
# the last value we've tried to write is remembered in the configuration.
self._value = map
if self.persist and self._device.persister:
self._device.persister[self.name] = map
data_bytes = self._validator.prepare_write(self._value)
if data_bytes is not None:
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings prepare map write(%s) => %r', self.name, self._value, data_bytes)
reply = self._rw.write(self._device, data_bytes)
if not reply:
return None
return map
def write_key_value(self, key, value):
assert hasattr(self, '_value')
assert hasattr(self, '_device')
assert key is not None
assert value is not None
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings write key %r value %r to %s', self.name, key, value, self._device)
if self._device.online:
# Remember the value we're trying to set, even if the write fails.
# This way even if the device is offline or some other error occurs,
# the last value we've tried to write is remembered in the configuration.
value = bool(value)
self._value[str(key)] = value
if self.persist and self._device.persister:
self._device.persister[self.name] = self._value
data_bytes = self._validator.prepare_write(self._value)
if data_bytes is not None:
if _log.isEnabledFor(_DEBUG):
_log.debug('%s: settings prepare key value write(%s,%s) => %r', self.name, key, str(value), data_bytes)
reply = self._rw.write(self._device, data_bytes)
if not reply:
# tell whomever is calling that the write failed
return None
return value
#
# read/write low-level operators
#
class RegisterRW(object):
__slots__ = ('register', )
kind = _NamedInt(0x01, 'register')
def __init__(self, register):
assert isinstance(register, int)
self.register = register
def read(self, device):
return device.read_register(self.register)
def write(self, device, data_bytes):
return device.write_register(self.register, data_bytes)
class FeatureRW(object):
__slots__ = ('feature', 'read_fnid', 'write_fnid', 'no_reply')
kind = _NamedInt(0x02, 'feature')
default_read_fnid = 0x00
default_write_fnid = 0x10
def __init__(self, feature, read_fnid=default_read_fnid, write_fnid=default_write_fnid, no_reply=False):
assert isinstance(feature, _NamedInt)
self.feature = feature
self.read_fnid = read_fnid
self.write_fnid = write_fnid
self.no_reply = no_reply
def read(self, device):
assert self.feature is not None
return device.feature_request(self.feature, self.read_fnid)
def write(self, device, data_bytes):
assert self.feature is not None
reply = device.feature_request(self.feature, self.write_fnid, data_bytes, no_reply=self.no_reply)
return reply if not self.no_reply else True
class FeatureRWMap(FeatureRW):
kind = _NamedInt(0x02, 'feature')
default_read_fnid = 0x00
default_write_fnid = 0x10
default_key_byte_count = 1
def __init__(
self,
feature,
read_fnid=default_read_fnid,
write_fnid=default_write_fnid,
key_byte_count=default_key_byte_count,
no_reply=False
):
assert isinstance(feature, _NamedInt)
self.feature = feature
self.read_fnid = read_fnid
self.write_fnid = write_fnid
self.key_byte_count = key_byte_count
self.no_reply = no_reply
def read(self, device, key):
assert self.feature is not None
key_bytes = _int2bytes(key, self.key_byte_count)
return device.feature_request(self.feature, self.read_fnid, key_bytes)
def write(self, device, key, data_bytes):
assert self.feature is not None
key_bytes = _int2bytes(key, self.key_byte_count)
reply = device.feature_request(self.feature, self.write_fnid, key_bytes, data_bytes, no_reply=self.no_reply)
return reply if not self.no_reply else True
#
# value validators
# handle the conversion from read bytes, to setting value, and back
#
class BooleanValidator(object):
__slots__ = ('true_value', 'false_value', 'mask', 'needs_current_value')
kind = KIND.toggle
default_true = 0x01
default_false = 0x00
# mask specifies all the affected bits in the value
default_mask = 0xFF
def __init__(self, true_value=default_true, false_value=default_false, mask=default_mask):
if isinstance(true_value, int):
assert isinstance(false_value, int)
if mask is None:
mask = self.default_mask
else:
assert isinstance(mask, int)
assert true_value & false_value == 0
assert true_value & mask == true_value
assert false_value & mask == false_value
self.needs_current_value = (mask != self.default_mask)
elif isinstance(true_value, bytes):
if false_value is None or false_value == self.default_false:
false_value = b'\x00' * len(true_value)
else:
assert isinstance(false_value, bytes)
if mask is None or mask == self.default_mask:
mask = b'\xFF' * len(true_value)
else:
assert isinstance(mask, bytes)
assert len(mask) == len(true_value) == len(false_value)
tv = _bytes2int(true_value)
fv = _bytes2int(false_value)
mv = _bytes2int(mask)
assert tv != fv # true and false might be something other than bit values
assert tv & mv == tv
assert fv & mv == fv
self.needs_current_value = any(m != b'\xFF' for m in mask)
else:
raise Exception("invalid mask '%r', type %s" % (mask, type(mask)))
self.true_value = true_value
self.false_value = false_value
self.mask = mask
def validate_read(self, reply_bytes):
if isinstance(self.mask, int):
reply_value = ord(reply_bytes[:1]) & self.mask
if _log.isEnabledFor(_DEBUG):
_log.debug('BooleanValidator: validate read %r => %02X', reply_bytes, reply_value)
if reply_value == self.true_value:
return True
if reply_value == self.false_value:
return False
_log.warn(
'BooleanValidator: reply %02X mismatched %02X/%02X/%02X', reply_value, self.true_value, self.false_value,
self.mask
)
return False
count = len(self.mask)
mask = _bytes2int(self.mask)
reply_value = _bytes2int(reply_bytes[:count]) & mask
true_value = _bytes2int(self.true_value)
if reply_value == true_value:
return True
false_value = _bytes2int(self.false_value)
if reply_value == false_value:
return False
_log.warn('BooleanValidator: reply %r mismatched %r/%r/%r', reply_bytes, self.true_value, self.false_value, self.mask)
return False
def prepare_write(self, new_value, current_value=None):
if new_value is None:
new_value = False
else:
assert isinstance(new_value, bool)
to_write = self.true_value if new_value else self.false_value
if isinstance(self.mask, int):
if current_value is not None and self.needs_current_value:
to_write |= ord(current_value[:1]) & (0xFF ^ self.mask)
if current_value is not None and to_write == ord(current_value[:1]):
return None
else:
to_write = bytearray(to_write)
count = len(self.mask)
for i in range(0, count):
b = ord(to_write[i:i + 1])
m = ord(self.mask[i:i + 1])
assert b & m == b
# b &= m
if current_value is not None and self.needs_current_value:
b |= ord(current_value[i:i + 1]) & (0xFF ^ m)
to_write[i] = b
to_write = bytes(to_write)
if current_value is not None and to_write == current_value[:len(to_write)]:
return None
if _log.isEnabledFor(_DEBUG):
_log.debug('BooleanValidator: prepare_write(%s, %s) => %r', new_value, current_value, to_write)
return to_write
class BitFieldValidator(object):
__slots__ = ('byte_count', 'options')
kind = KIND.multiple_toggle
def __init__(self, options, byte_count=None):
assert (isinstance(options, list))
self.options = options
self.byte_count = (max(x.bit_length() for x in options) + 7) // 8
if byte_count:
assert (isinstance(byte_count, int) and byte_count >= self.byte_count)
self.byte_count = byte_count
def validate_read(self, reply_bytes):
r = _bytes2int(reply_bytes[:self.byte_count])
value = {str(int(k)): False for k in self.options}
m = 1
for _ in range(8 * self.byte_count):
if m in self.options:
value[str(int(m))] = bool(r & m)
m <<= 1
return value
def prepare_write(self, new_value):
assert (isinstance(new_value, dict))
w = 0
for k, v in new_value.items():
if v:
w |= int(k)
return _int2bytes(w, self.byte_count)
class ChoicesValidator(object):
kind = KIND.choice
"""Translates between NamedInts and a byte sequence.
:param choices: a list of NamedInts
:param byte_count: the size of the derived byte sequence. If None, it
will be calculated from the choices."""
def __init__(self, choices, byte_count=None, read_skip_byte_count=None, write_prefix_bytes=b''):
assert choices is not None
assert isinstance(choices, _NamedInts)
assert len(choices) > 1
self.choices = choices
self.needs_current_value = False
max_bits = max(x.bit_length() for x in choices)
self._byte_count = (max_bits // 8) + (1 if max_bits % 8 else 0)
if byte_count:
assert self._byte_count <= byte_count
self._byte_count = byte_count
assert self._byte_count < 8
self._read_skip_byte_count = read_skip_byte_count if read_skip_byte_count else 0
self._write_prefix_bytes = write_prefix_bytes if write_prefix_bytes else b''
assert self._byte_count + self._read_skip_byte_count <= 14
assert self._byte_count + len(self._write_prefix_bytes) <= 14
def validate_read(self, reply_bytes):
reply_value = _bytes2int(reply_bytes[self._read_skip_byte_count:self._read_skip_byte_count + self._byte_count])
valid_value = self.choices[reply_value]
assert valid_value is not None, '%s: failed to validate read value %02X' % (self.__class__.__name__, reply_value)
return valid_value
def prepare_write(self, new_value, current_value=None):
if new_value is None:
choice = self.choices[:][0]
else:
if isinstance(new_value, int):
choice = self.choices[new_value]
elif int(new_value) in self.choices:
choice = self.choices[int(new_value)]
elif new_value in self.choices:
choice = self.choices[new_value]
else:
raise ValueError(new_value)
if choice is None:
raise ValueError('invalid choice %r' % new_value)
assert isinstance(choice, _NamedInt)
return self._write_prefix_bytes + choice.bytes(self._byte_count)
class ChoicesMapValidator(ChoicesValidator):
kind = KIND.map_choice
def __init__(
self,
choices_map,
key_byte_count=None,
byte_count=None,
read_skip_byte_count=0,
write_prefix_bytes=b'',
extra_default=None
):
assert choices_map is not None
assert isinstance(choices_map, dict)
max_key_bits = 0
max_value_bits = 0
for key, choices in choices_map.items():
assert isinstance(key, _NamedInt)
assert isinstance(choices, list)
max_key_bits = max(max_key_bits, key.bit_length())
for key_value in choices:
assert isinstance(key_value, _NamedInt)
max_value_bits = max(max_value_bits, key_value.bit_length())
self._key_byte_count = (max_key_bits + 7) // 8
if key_byte_count:
assert self._key_byte_count <= key_byte_count
self._key_byte_count = key_byte_count
self._byte_count = (max_value_bits + 7) // 8
if byte_count:
assert self._byte_count <= byte_count
self._byte_count = byte_count
self.choices = choices_map
self.needs_current_value = False
self.extra_default = extra_default
self._read_skip_byte_count = read_skip_byte_count if read_skip_byte_count else 0
self._write_prefix_bytes = write_prefix_bytes if write_prefix_bytes else b''
assert self._byte_count + self._read_skip_byte_count + self._key_byte_count <= 14
assert self._byte_count + len(self._write_prefix_bytes) + self._key_byte_count <= 14
def validate_read(self, reply_bytes, key):
start = self._key_byte_count + self._read_skip_byte_count
end = start + self._byte_count
reply_value = _bytes2int(reply_bytes[start:end])
# reprogrammable keys starts out as 0, which is not a choice, so don't use assert here
if self.extra_default is not None and self.extra_default == reply_value:
return int(self.choices[key][0])
assert reply_value in self.choices[
key], '%s: failed to validate read value %02X' % (self.__class__.__name__, reply_value)
return reply_value
def prepare_write(self, key, new_value):
choices = self.choices[key]
if new_value not in choices and new_value != self.extra_default:
raise ValueError('invalid choice %r' % new_value)
return self._write_prefix_bytes + new_value.to_bytes(self._byte_count, 'big')
class RangeValidator(object):
__slots__ = ('min_value', 'max_value', 'flag', '_byte_count', 'needs_current_value')
kind = KIND.range
"""Translates between integers and a byte sequence.
:param min_value: minimum accepted value (inclusive)
:param max_value: maximum accepted value (inclusive)
:param byte_count: the size of the derived byte sequence. If None, it
will be calculated from the range."""
def __init__(self, min_value, max_value, byte_count=None):
assert max_value > min_value
self.min_value = min_value
self.max_value = max_value
self.needs_current_value = False
self._byte_count = math.ceil(math.log(max_value + 1, 256))
if byte_count:
assert self._byte_count <= byte_count
self._byte_count = byte_count
assert self._byte_count < 8
def validate_read(self, reply_bytes):
reply_value = _bytes2int(reply_bytes[:self._byte_count])
assert reply_value >= self.min_value, '%s: failed to validate read value %02X' % (self.__class__.__name__, reply_value)
assert reply_value <= self.max_value, '%s: failed to validate read value %02X' % (self.__class__.__name__, reply_value)
return reply_value
def prepare_write(self, new_value, current_value=None):
if new_value < self.min_value or new_value > self.max_value:
raise ValueError('invalid choice %r' % new_value)
return _int2bytes(new_value, self._byte_count)