67 lines
1.7 KiB
Python
67 lines
1.7 KiB
Python
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#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""从设备树复算 gpio-in-N 对应的全局 GPIO 号。"""
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from pathlib import Path
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from .config import DEVICETREE_BASE
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def _read_be32(path: Path, offset: int = 0):
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try:
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data = path.read_bytes()
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except OSError:
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return None
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if len(data) < offset + 4:
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return None
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return int.from_bytes(data[offset:offset + 4], "big")
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def derive_gpio(n: int, base_dir: str = DEVICETREE_BASE):
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"""从设备树复算 IN<n> 的全局 GPIO 号。
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返回 (gpio_num, label, pin) 或 None。
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"""
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base = Path(base_dir)
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f = base / f"gpio-in-{n}" / "control-gpios"
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if not f.exists():
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return None
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try:
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data = f.read_bytes()
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except OSError:
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return None
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if len(data) < 8:
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return None
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ph = int.from_bytes(data[0:4], "big")
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pin = int.from_bytes(data[4:8], "big")
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# phandle -> gpio-controller 节点
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ctrl = None
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for c in base.glob("gpio@*/gpio-controller@*"):
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cph = _read_be32(c / "phandle")
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if cph == ph:
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ctrl = c
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break
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if ctrl is None:
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return None
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bank = ctrl.parent.name
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if bank.startswith("gpio@"):
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bank = bank[len("gpio@"):]
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label = f"{bank}.gpio"
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# label -> gpiochip base
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gpio_class = Path("/sys/class/gpio")
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if not gpio_class.exists():
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return None
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for g in gpio_class.glob("gpiochip*"):
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try:
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if (g / "label").read_text().strip() == label:
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chip_base = int((g / "base").read_text().strip())
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return chip_base + pin, label, pin
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except (OSError, ValueError):
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continue
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return None
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