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One-KVM/kvmd/edid.py

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Python
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# ========================================================================== #
# #
# KVMD - The main PiKVM daemon. #
# #
# Copyright (C) 2018-2024 Maxim Devaev <mdevaev@gmail.com> #
# #
# 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 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 General Public License for more details. #
# #
# You should have received a copy of the GNU General Public License #
# along with this program. If not, see <https://www.gnu.org/licenses/>. #
# #
# ========================================================================== #
import os
import re
import dataclasses
import contextlib
from typing import IO
from typing import Generator
# =====
class EdidNoBlockError(Exception):
pass
@contextlib.contextmanager
def _smart_open(path: str, mode: str) -> Generator[IO, None, None]:
fd = (0 if "r" in mode else 1)
with (os.fdopen(fd, mode, closefd=False) if path == "-" else open(path, mode)) as file:
yield file
if "w" in mode:
file.flush()
@dataclasses.dataclass(frozen=True)
class _CeaBlock:
tag: int
data: bytes
def __post_init__(self) -> None:
assert 0 < self.tag <= 0b111
assert 0 < len(self.data) <= 0b11111
@property
def size(self) -> int:
return len(self.data) + 1
def pack(self) -> bytes:
header = (self.tag << 5) | len(self.data)
return header.to_bytes() + self.data
@classmethod
def first_from_raw(cls, raw: (bytes | list[int])) -> "_CeaBlock":
assert 0 < raw[0] <= 0xFF
tag = (raw[0] & 0b11100000) >> 5
data_size = (raw[0] & 0b00011111)
data = bytes(raw[1:data_size + 1])
return _CeaBlock(tag, data)
_LONG = 256
_SHORT = 128
_CEA = 128
_CEA_AUDIO = 1
_CEA_SPEAKERS = 4
class Edid:
# https://en.wikipedia.org/wiki/Extended_Display_Identification_Data
def __init__(self, data: bytes) -> None:
assert len(data) in [_SHORT, _LONG], f"Invalid EDID length: {len(data)}, should be {_SHORT} or {_LONG} bytes"
self.__long = (len(data) == _LONG)
if self.__long:
assert data[126] == 1, "Zero extensions number"
assert (data[_CEA + 0], data[_CEA + 1]) == (0x02, 0x03), "Can't find CEA extension"
self.__data = list(data)
@classmethod
def is_header_valid(cls, data: bytes) -> bool:
return data.startswith(b"\x00\xFF\xFF\xFF\xFF\xFF\xFF\x00")
@classmethod
def from_file(cls, path: str) -> "Edid":
with _smart_open(path, "rb") as file:
data = file.read()
if not cls.is_header_valid(data):
text = re.sub(r"\s", "", data.decode())
data = bytes([
int(text[index:index + 2], 16)
for index in range(0, len(text), 2)
])
return Edid(data)
def write_hex(self, path: str) -> None:
self.__update_checksums()
text = "\n".join(
"".join(
f"{item:0{2}X}"
for item in self.__data[index:index + 16]
)
for index in range(0, len(self.__data), 16)
) + "\n"
with _smart_open(path, "w") as file:
file.write(text)
def write_bin(self, path: str) -> None:
self.__update_checksums()
with _smart_open(path, "wb") as file:
file.write(bytes(self.__data))
def __update_checksums(self) -> None:
self.__data[127] = 256 - (sum(self.__data[:127]) % 256)
if self.__long:
self.__data[255] = 256 - (sum(self.__data[128:255]) % 256)
# =====
def get_mfc_id(self) -> str:
raw = self.__data[8] << 8 | self.__data[9]
return bytes([
((raw >> 10) & 0b11111) + 0x40,
((raw >> 5) & 0b11111) + 0x40,
(raw & 0b11111) + 0x40,
]).decode("ascii")
def set_mfc_id(self, mfc_id: str) -> None:
assert len(mfc_id) == 3, "Mfc ID must be 3 characters long"
data = mfc_id.upper().encode("ascii")
for ch in data:
assert 0x41 <= ch <= 0x5A, "Mfc ID must contain only A-Z characters"
raw = (
(data[2] - 0x40)
| ((data[1] - 0x40) << 5)
| ((data[0] - 0x40) << 10)
)
self.__data[8] = (raw >> 8) & 0xFF
self.__data[9] = raw & 0xFF
# =====
def get_product_id(self) -> int:
return (self.__data[10] | self.__data[11] << 8)
def set_product_id(self, product_id: int) -> None:
assert 0 <= product_id <= 0xFFFF, f"Product ID should be from 0 to {0xFFFF}"
self.__data[10] = product_id & 0xFF
self.__data[11] = (product_id >> 8) & 0xFF
# =====
def get_serial(self) -> int:
return (
self.__data[12]
| self.__data[13] << 8
| self.__data[14] << 16
| self.__data[15] << 24
)
def set_serial(self, serial: int) -> None:
assert 0 <= serial <= 0xFFFFFFFF, f"Serial should be from 0 to {0xFFFFFFFF}"
self.__data[12] = serial & 0xFF
self.__data[13] = (serial >> 8) & 0xFF
self.__data[14] = (serial >> 16) & 0xFF
self.__data[15] = (serial >> 24) & 0xFF
# =====
def get_monitor_name(self) -> str:
return self.__get_dtd_text(0xFC, "Monitor Name")
def set_monitor_name(self, text: str) -> None:
self.__set_dtd_text(0xFC, "Monitor Name", text)
def get_monitor_serial(self) -> str:
return self.__get_dtd_text(0xFF, "Monitor Serial")
def set_monitor_serial(self, text: str) -> None:
self.__set_dtd_text(0xFF, "Monitor Serial", text)
def __get_dtd_text(self, d_type: int, name: str) -> str:
index = self.__find_dtd_text(d_type, name)
return bytes(self.__data[index:index + 13]).decode("cp437").strip()
def __set_dtd_text(self, d_type: int, name: str, text: str) -> None:
index = self.__find_dtd_text(d_type, name)
encoded = (text[:13] + "\n" + " " * 12)[:13].encode("cp437")
for (offset, ch) in enumerate(encoded):
self.__data[index + offset] = ch
def __find_dtd_text(self, d_type: int, name: str) -> int:
for index in [54, 72, 90, 108]:
if self.__data[index + 3] == d_type:
return index + 5
raise EdidNoBlockError(f"Can't find DTD {name}")
# ===== CEA =====
def get_audio(self) -> bool:
(cbs, _) = self.__parse_cea()
audio = False
speakers = False
for cb in cbs:
if cb.tag == _CEA_AUDIO:
audio = True
elif cb.tag == _CEA_SPEAKERS:
speakers = True
return (audio and speakers and self.__get_basic_audio())
def set_audio(self, enabled: bool) -> None:
(cbs, dtds) = self.__parse_cea()
cbs = [cb for cb in cbs if cb.tag not in [_CEA_AUDIO, _CEA_SPEAKERS]]
if enabled:
cbs.append(_CeaBlock(_CEA_AUDIO, b"\x09\x7f\x07"))
cbs.append(_CeaBlock(_CEA_SPEAKERS, b"\x01\x00\x00"))
self.__replace_cea(cbs, dtds)
self.__set_basic_audio(enabled)
def __get_basic_audio(self) -> bool:
return bool(self.__data[_CEA + 3] & 0b01000000)
def __set_basic_audio(self, enabled: bool) -> None:
if enabled:
self.__data[_CEA + 3] |= 0b01000000
else:
self.__data[_CEA + 3] &= (0xFF - 0b01000000) # ~X
def __parse_cea(self) -> tuple[list[_CeaBlock], bytes]:
if not self.__long:
raise EdidNoBlockError("This EDID does not contain any CEA blocks")
cea = self.__data[_CEA:]
dtd_begin = cea[2]
if dtd_begin == 0:
return ([], b"")
cbs: list[_CeaBlock] = []
if dtd_begin > 4:
raw = cea[4:dtd_begin]
while len(raw) != 0:
cb = _CeaBlock.first_from_raw(raw)
cbs.append(cb)
raw = raw[cb.size:]
dtds = b""
assert dtd_begin >= 4
raw = cea[dtd_begin:]
while len(raw) > (18 + 1) and raw[0] != 0:
dtds += bytes(raw[:18])
raw = raw[18:]
return (cbs, dtds)
def __replace_cea(self, cbs: list[_CeaBlock], dtds: bytes) -> None:
cbs_packed = b""
for cb in cbs:
cbs_packed += cb.pack()
raw = cbs_packed + dtds
assert len(raw) <= (128 - 4 - 1), "Too many CEA blocks or DTDs"
self.__data[_CEA + 2] = (0 if len(raw) == 0 else (len(cbs_packed) + 4))
for index in range(4, 127):
try:
ch = raw[index - 4]
except IndexError:
ch = 0
self.__data[_CEA + index] = ch
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