utils: add ioctl_macros module

Signed-off-by: Eric Callahan <arksine.code@gmail.com>

moonraker/utils/ioctl_macros.py

@@ -0,0 +1,77 @@
+# Methods to create IOCTL requests
+#
+# Copyright (C) 2023 Eric Callahan <arksine.code@gmail.com>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license
+
+from __future__ import annotations
+import ctypes
+from typing import Union, Type, TYPE_CHECKING
+
+"""
+This module contains of Python port of the macros avaialble in
+"/include/uapi/asm-generic/ioctl.h" from the linux kernel.
+"""
+
+if TYPE_CHECKING:
+    IOCParamSize = Union[int, str, Type[ctypes._SimpleCData]]
+
+_IOC_NRBITS = 8
+_IOC_TYPEBITS = 8
+
+# NOTE: The following could be platform specific.
+_IOC_SIZEBITS = 14
+_IOC_DIRBITS = 2
+
+_IOC_NRMASK = (1 << _IOC_NRBITS) - 1
+_IOC_TYPEMASK = (1 << _IOC_TYPEBITS) - 1
+_IOC_SIZEMASK = (1 << _IOC_SIZEBITS) - 1
+_IOC_DIRMASK = (1 << _IOC_DIRBITS) - 1
+
+_IOC_NRSHIFT = 0
+_IOC_TYPESHIFT = _IOC_NRSHIFT + _IOC_NRBITS
+_IOC_SIZESHIFT = _IOC_TYPESHIFT + _IOC_TYPEBITS
+_IOC_DIRSHIFT = _IOC_SIZESHIFT + _IOC_SIZEBITS
+
+# The constants below may also be platform specific
+IOC_NONE = 0
+IOC_WRITE = 1
+IOC_READ = 2
+
+def _check_value(val: int, name: str, maximum: int):
+    if val > maximum:
+        raise ValueError(f"Value '{val}' for '{name}' exceeds max of {maximum}")
+
+def _IOC_TYPECHECK(param_size: IOCParamSize) -> int:
+    if isinstance(param_size, int):
+        return param_size
+    elif isinstance(param_size, bytearray):
+        return len(param_size)
+    elif isinstance(param_size, str):
+        ctcls = getattr(ctypes, param_size)
+        return ctypes.sizeof(ctcls)
+    return ctypes.sizeof(param_size)
+
+def IOC(direction: int, cmd_type: int, cmd_number: int, param_size: int) -> int:
+    _check_value(direction, "direction", _IOC_DIRMASK)
+    _check_value(cmd_type, "cmd_type", _IOC_TYPEMASK)
+    _check_value(cmd_number, "cmd_number", _IOC_NRMASK)
+    _check_value(param_size, "ioc_size", _IOC_SIZEMASK)
+    return (
+        (direction << _IOC_DIRSHIFT) |
+        (param_size << _IOC_SIZESHIFT) |
+        (cmd_type << _IOC_TYPESHIFT) |
+        (cmd_number << _IOC_NRSHIFT)
+    )
+
+def IO(cmd_type: int, cmd_number: int) -> int:
+    return IOC(IOC_NONE, cmd_type, cmd_number, 0)
+
+def IOR(cmd_type: int, cmd_number: int, param_size: IOCParamSize) -> int:
+    return IOC(IOC_READ, cmd_type, cmd_number, _IOC_TYPECHECK(param_size))
+
+def IOW(cmd_type: int, cmd_number: int, param_size: IOCParamSize) -> int:
+    return IOC(IOC_WRITE, cmd_type, cmd_number, _IOC_TYPECHECK(param_size))
+
+def IOWR(cmd_type: int, cmd_number: int, param_size: IOCParamSize) -> int:
+    return IOC(IOC_READ | IOC_WRITE, cmd_type, cmd_number, _IOC_TYPECHECK(param_size))