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Add readonly parameter to InputDevice and writable parameter to list_devices/is_device #251

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Add readonly parameter to InputDevice and writable parameter to list_devices/is_device #251

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9 changes: 8 additions & 1 deletion src/evdev/device.py
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Original file line number Diff line number Diff line change
Expand Up @@ -109,19 +109,26 @@ class InputDevice(EventIO, Generic[_AnyStr]):

__slots__ = ("path", "fd", "info", "name", "phys", "uniq", "_rawcapabilities", "version", "ff_effects_count")

def __init__(self, dev: Union[_AnyStr, "os.PathLike[_AnyStr]"]):
def __init__(self, dev: Union[_AnyStr, "os.PathLike[_AnyStr]"], readonly: bool = False):
"""
Arguments
---------
dev : str|bytes|PathLike
Path to input device
readonly : bool
If True, the device is opened in read-only mode (``O_RDONLY``)
without attempting ``O_RDWR`` first. This avoids triggering
firmware side-effects (such as LED state re-assertion) on
certain hardware. Default is False.
"""

#: Path to input device.
self.path: _AnyStr = dev if not hasattr(dev, "__fspath__") else dev.__fspath__()

# Certain operations are possible only when the device is opened in read-write mode.
try:
if readonly:
raise OSError
fd = os.open(dev, os.O_RDWR | os.O_NONBLOCK)
except OSError:
fd = os.open(dev, os.O_RDONLY | os.O_NONBLOCK)
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31 changes: 25 additions & 6 deletions src/evdev/util.py
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Expand Up @@ -9,15 +9,33 @@
from .events import InputEvent, event_factory, KeyEvent, RelEvent, AbsEvent, SynEvent


def list_devices(input_device_dir: Union[str, bytes, os.PathLike] = "/dev/input") -> List[str]:
"""List readable character devices in ``input_device_dir``."""
def list_devices(input_device_dir: Union[str, bytes, os.PathLike] = "/dev/input", writable: bool = True) -> List[str]:
"""List readable (and optionally writable) character devices in ``input_device_dir``.

Arguments
---------
input_device_dir : str|bytes|PathLike
Path to the input device directory. Default is ``/dev/input``.
writable : bool
If True (default), only list devices that are both readable and
writable. If False, list all readable devices.
"""

fns = glob.glob("{}/event*".format(input_device_dir))
return list(filter(is_device, fns))
return list(filter(lambda fn: is_device(fn, writable=writable), fns))


def is_device(fn: Union[str, bytes, os.PathLike], writable: bool = True) -> bool:
"""Check if ``fn`` is a readable (and optionally writable) character device.

def is_device(fn: Union[str, bytes, os.PathLike]) -> bool:
"""Check if ``fn`` is a readable and writable character device."""
Arguments
---------
fn : str|bytes|PathLike
Path to the device file.
writable : bool
If True (default), also check for write access. If False, only
check for read access.
"""

if not os.path.exists(fn):
return False
Expand All @@ -26,7 +44,8 @@ def is_device(fn: Union[str, bytes, os.PathLike]) -> bool:
if not stat.S_ISCHR(m):
return False

if not os.access(fn, os.R_OK | os.W_OK):
access = os.R_OK | os.W_OK if writable else os.R_OK
if not os.access(fn, access):
return False

return True
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