fix: ignore resetting on unsupported ports

Closes https://github.com/espressif/esptool/issues/762

esptool/reset.py

@@ -3,11 +3,12 @@
 #
 # SPDX-License-Identifier: GPL-2.0-or-later
 
+import errno
 import os
 import struct
 import time
 
-from .util import FatalError
+from .util import FatalError, PrintOnce
 
 # Used for resetting into bootloader on Unix-like systems
 if os.name != "nt":
@@ -26,11 +27,28 @@ DEFAULT_RESET_DELAY = 0.05  # default time to wait before releasing boot pin aft
 
 
 class ResetStrategy(object):
+    print_once = PrintOnce()
+
     def __init__(self, port, reset_delay=DEFAULT_RESET_DELAY):
         self.port = port
         self.reset_delay = reset_delay
 
-    def __call__():
+    def __call__(self):
+        try:
+            self.reset()
+        except OSError as e:
+            # ENOTTY for TIOCMSET; EINVAL for TIOCMGET
+            if e.errno in [errno.ENOTTY, errno.EINVAL]:
+                self.print_once(
+                    "WARNING: Chip was NOT reset. Setting RTS/DTR lines is not "
+                    f"supported for port '{self.port.name}'. Set --before and --after "
+                    "arguments to 'no_reset' and switch to bootloader manually to "
+                    "avoid this warning."
+                )
+            else:
+                raise
+
+    def reset(self):
         pass
 
     def _setDTR(self, state):
@@ -63,7 +81,7 @@ class ClassicReset(ResetStrategy):
     Classic reset sequence, sets DTR and RTS lines sequentially.
     """
 
-    def __call__(self):
+    def reset(self):
         self._setDTR(False)  # IO0=HIGH
         self._setRTS(True)  # EN=LOW, chip in reset
         time.sleep(0.1)
@@ -79,7 +97,7 @@ class UnixTightReset(ResetStrategy):
     which allows setting DTR and RTS lines at the same time.
     """
 
-    def __call__(self):
+    def reset(self):
         self._setDTRandRTS(False, False)
         self._setDTRandRTS(True, True)
         self._setDTRandRTS(False, True)  # IO0=HIGH & EN=LOW, chip in reset
@@ -96,7 +114,7 @@ class USBJTAGSerialReset(ResetStrategy):
     is connecting via its USB-JTAG-Serial peripheral.
     """
 
-    def __call__(self):
+    def reset(self):
         self._setRTS(False)
         self._setDTR(False)  # Idle
         time.sleep(0.1)
@@ -121,7 +139,7 @@ class HardReset(ResetStrategy):
         super().__init__(port)
         self.uses_usb_otg = uses_usb_otg
 
-    def __call__(self):
+    def reset(self):
         self._setRTS(True)  # EN->LOW
         if self.uses_usb_otg:
             # Give the chip some time to come out of reset,
@@ -162,7 +180,7 @@ class CustomReset(ResetStrategy):
         "U": "self._setDTRandRTS({})",
     }
 
-    def __call__(self):
+    def reset(self):
         exec(self.constructed_strategy)
 
     def __init__(self, port, seq_str):

esptool/util.py

@@ -99,6 +99,20 @@ def get_file_size(path_to_file):
     return file_size
 
 
+class PrintOnce:
+    """
+    Class for printing messages just once. Can be useful when running in a loop
+    """
+
+    def __init__(self) -> None:
+        self.already_printed = False
+
+    def __call__(self, text) -> None:
+        if not self.already_printed:
+            print(text)
+            self.already_printed = True
+
+
 class FatalError(RuntimeError):
     """
     Wrapper class for runtime errors that aren't caused by internal bugs, but by

test/test_esptool.py

@@ -1204,6 +1204,30 @@ class TestVirtualPort(TestAutoDetect):
             )
         self.verify_readback(0, 50 * 1024, "images/fifty_kb.bin")
 
+    @pytest.fixture
+    def pty_port(self):
+        import pty
+
+        master_fd, slave_fd = pty.openpty()
+        yield os.ttyname(slave_fd)
+        os.close(master_fd)
+        os.close(slave_fd)
+
+    @pytest.mark.host_test
+    def test_pty_port(self, pty_port):
+        cmd = [sys.executable, "-m", "esptool", "--port", pty_port, "chip_id"]
+        output = subprocess.run(
+            cmd,
+            cwd=TEST_DIR,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+        )
+        # no chip connected so command should fail
+        assert output.returncode != 0
+        output = output.stdout.decode("utf-8")
+        print(output)  # for logging
+        assert "WARNING: Chip was NOT reset." in output
+
 
 @pytest.mark.quick_test
 class TestReadWriteMemory(EsptoolTestCase):