processing udc state

kvmd/plugins/hid/otg/usb.py

@@ -0,0 +1,76 @@
+# ========================================================================== #
+#                                                                            #
+#    KVMD - The main Pi-KVM daemon.                                          #
+#                                                                            #
+#    Copyright (C) 2018  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
+
+from ....logging import get_logger
+
+from .... import env
+
+
+# =====
+class UsbDeviceController:
+    # Проблема в том, что устройство может отвечать EAGAIN или ESHUTDOWN,
+    # если оно было отключено физически. См:
+    #    - https://github.com/raspberrypi/linux/issues/3870
+    #    - https://github.com/raspberrypi/linux/pull/3151
+    # Так что нам нужно проверять состояние контроллера, чтобы не спамить
+    # в устройство и отслеживать его состояние.
+
+    def __init__(self, udc: str) -> None:
+        self.__udc = udc
+        self.__state_path = ""
+
+    def find(self) -> None:
+        logger = get_logger()
+
+        path = f"{env.SYSFS_PREFIX}/sys/class/udc"
+        try:
+            candidates = sorted(os.listdir(path))
+        except Exception as err:
+            logger.error("Can't list %s: %s: %s", path, type(err).__name__, err)
+            return
+
+        udc = ""
+        if not self.__udc:
+            if len(candidates) == 0:
+                logger.warning("Can't find any UDC: ignored")
+            else:
+                udc = candidates[0]
+        elif self.__udc not in candidates:
+            logger.warning("Can't find selected UDC: %s: ignored", self.__udc)
+        else:
+            udc = self.__udc
+
+        if udc:
+            get_logger().info("Using UDC %s", udc)
+            self.__state_path = os.path.join(path, udc, "state")
+
+    def can_operate(self) -> bool:
+        if self.__state_path:
+            try:
+                with open(self.__state_path, "r") as state_file:
+                    # https://www.maxlinear.com/Files/Documents/an213_033111.pdf
+                    return (state_file.read().strip().lower() == "configured")
+            except Exception:
+                pass
+        return True  # При ошибке лучше прикинуться работающим, мало ли что