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#!/usr/bin/env python3
#
# libssc: Library to expose Qualcomm Sensor Core sensors
# Copyright (C) 2022-2025 Dylan Van Assche
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published
# by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
#
import sys
from enum import Enum
from typing import Tuple
class ValueType(Enum):
INT = 0
ARRAY = 1
SEQUENCE = 2
class MessageType(Enum):
REQUEST = 0
RESPONSE = 2
INDICATION = 4
UNKNOWN = sys.maxsize
class QMI():
"""QMI messages encoding and decoding functions."""
@staticmethod
def parse_header(message: bytes) -> Tuple[MessageType, int, int, bytes]:
"""
Parse a QMI header to extract:
- Type of message (uint8)
- Transaction ID (uint16)
- Message ID (uint16)
- Message length (uint16)
Parameters
----------
message : bytes
Raw QMI message as bytes (little endian).
Returns
-------
message_type : MessageType
Type of message e.g., REQUEST, RESPONSE, or INDICATION.
transaction_id : int
ID of the transaction for concurrent messages.
message_id : int
ID of the message, specific for the QMI service.
message_length : int
Length of the message in bytes.
"""
# QMI message type
if message[0] == MessageType.REQUEST.value:
message_type = MessageType.REQUEST
elif message[0] == MessageType.RESPONSE.value:
message_type = MessageType.RESPONSE
elif message[0] == MessageType.INDICATION.value:
message_type = MessageType.INDICATION
else:
print(f'Unknown message type: {message[0]}', file=sys.stderr)
message_type = MessageType.UNKNOWN
# QMI transaction ID
transaction_id = int.from_bytes(message[1:3], byteorder='little')
# QMI message ID
message_id = int.from_bytes(message[3:5], byteorder='little')
# QMI message length
message_length = int.from_bytes(message[5:7], byteorder='little')
return message_type, transaction_id, message_id, message_length
@staticmethod
def generate_header(message_type: MessageType, transaction_id: int, message_id: int) -> bytes:
"""
Generate a QMI message with no TLVs and a QMI header.
Parameters
----------
message_type : MessageType
Type of QMI message
transaction_id : int
ID of the transaction.
message_id : int
ID of the message for the specific QMI service.
Returns
-------
message : bytes
Raw QMI message as bytes (little endian).
"""
message = bytes()
message += message_type.value.to_bytes(1, byteorder='little')
message += transaction_id.to_bytes(2, byteorder='little')
message += message_id.to_bytes(2, byteorder='little')
message += (len(message) + 2).to_bytes(2, byteorder='little')
return message
@staticmethod
def parse_tlv(message: bytes, tlv: int, value_type: ValueType) -> Tuple[int, int, bytes]:
"""
Parse QMI TLV in a QMI message to extract:
- Type (uint8)
- Length (uint16)
- Value (bytes)
Parameters
----------
message : bytes
Raw QMI message as bytes (little endian).
Returns
-------
tlvs : dict
Dictionary of TLVs extracted with Type as dictionary's key
and Value as dictionary's value. Length is implied.
"""
message_type, transaction_id, message_id, message_length = QMI.parse_header(message)
# Strip QMI header
tlvs = message[7:]
# Iterate over all TLVs
offset = 0
tlv_id = 0
while offset < len(tlvs):
tlv_type = int.from_bytes(tlvs[0+offset:1+offset], byteorder='little')
tlv_length = int.from_bytes(tlvs[1+offset:3+offset], byteorder='little')
tlv_value = tlvs[3+offset:3+tlv_length+offset]
offset += 1 + 2 + tlv_length
tlv_id += 1
# Strip array length from QMI TLV value
if value_type == ValueType.INT or value_type == ValueType.SEQUENCE:
tlv_value = int.from_bytes(tlv_value, byteorder='little')
elif value_type == ValueType.ARRAY:
tlv_value = tlv_value[2:]
# Look for TLV in message, skip others
if tlv != tlv_type:
continue
return tlv_type, tlv_length, tlv_value
@staticmethod
def generate_tlv(message: bytes, tlv_id: int, tlv_value: bytes, value_type: ValueType) -> bytes:
"""
Generate a QMI TLV and add it to the message.
Parameters
----------
message : bytes
Raw QMI message as bytes (little endian).
tlv_id : int
TLV Type.
tlv_value : bytes
TLV Value.
value_type : ValueType
Type of the TLV Value.
Returns
-------
message : bytes
Raw QMI message as bytes (little endian).
"""
# Add TLV and calculate its length
message += tlv_id.to_bytes(1, byteorder='little')
if value_type == ValueType.ARRAY:
message += (len(tlv_value) + 2).to_bytes(2, byteorder='little')
elif value_type == ValueType.INT or value_type == ValueType.SEQUENCE:
message += len(tlv_value).to_bytes(2, byteorder='little')
else:
print(f'Unknown value type: {value_type}', file=sys.stderr)
if value_type == ValueType.ARRAY:
value_array_length = len(tlv_value)
message += value_array_length.to_bytes(2, byteorder='little')
message += tlv_value
# Update QMI header length
qmi_length = int.from_bytes(message[5:7], byteorder='little')
message = message[:5] + \
(len(message) - 7).to_bytes(2, byteorder='little') + \
message[7:]
return message
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