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Ignore EPERM when setting low latency #144

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Merged
puddly merged 3 commits into from
Oct 22, 2026
Merged

Ignore EPERM when setting low latency #144

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ee27e07
Ignore `EPERM` when setting low latency
puddly Oct 22, 2026
7986f83
Add a test
puddly Oct 22, 2026
0cfd7a5
Swap back to Linux-only tests
puddly Oct 22, 2026
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2 changes: 2 additions & 0 deletions serialx/platforms/serial_linux.py
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Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,8 @@ def _after_configure_port(self) -> None:
except OSError as exc:
if exc.errno in (errno.ENOTTY, errno.EOPNOTSUPP):
LOGGER.debug("Device does not support setting low latency")
elif exc.errno == errno.EPERM:
LOGGER.debug("User does not have permission to set low latency")
else:
raise

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12 changes: 10 additions & 2 deletions tests/test_serial_linux.py
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Original file line number Diff line number Diff line change
Expand Up @@ -101,15 +101,23 @@ def test_set_non_posix_baudrate_zero_speed_raises() -> None:
assert captured == []


@pytest.mark.parametrize(
"err",
[
OSError(errno.EOPNOTSUPP, "Not supported"),
OSError(errno.ENOTTY, "Inappropriate ioctl for device"),
OSError(errno.EPERM, "Operation not permitted"),
],
)
@patch("serialx.platforms.serial_linux.TIOCGSERIAL", TIOCGSERIAL)
@patch("serialx.platforms.serial_linux.TIOCSSERIAL", TIOCSSERIAL)
def test_tiocgserial_ioctl_not_supported() -> None:
def test_tiocgserial_ioctl_not_supported(err: OSError) -> None:
"""Test that TIOCGSERIAL ioctl not supported is handled gracefully."""
ioctl_orig = fcntl.ioctl

def ioctl(fd: int, request: int, arg: Any = 0, mutate_flag: bool = True) -> Any:
if request in (TIOCGSERIAL, TIOCSSERIAL):
raise OSError(errno.EOPNOTSUPP, "Not supported")
raise err

return ioctl_orig(fd, request, arg, mutate_flag)

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