Fixes #64 - First implementation for libusb1-based hotplug #160

roberthartung · 2016-10-24T08:25:01Z

No description provided.

walac · 2016-11-07T21:24:16Z

@roberthartung sorry, I didn't forget your PR, crazy weeks...

ijager · 2017-01-23T12:34:40Z

Do you have any idea when you are going to look at this? I would love to use hotplugging.

walac · 2017-01-23T12:40:41Z

@ijager I lost my test hardware, I am working on a solution for that, that's why I stalled more serious patches for the project.

roberthartung · 2017-02-14T03:32:46Z

@ijager You can add my repo as an upstream in the meantime and cherry pick the commit!

roberthartung · 2017-08-11T07:43:08Z

I just uploaded a bugfix for user_data in the hotplug handle

hetsch · 2017-09-19T15:21:56Z

Oh yes, please consider merging this pull request!

braineo · 2018-02-15T08:27:20Z

cool this works. Maybe maintainers can consider merging this PR or discuss what issues are remaining to fix?

roberthartung · 2018-04-27T07:34:57Z

@walac Any news?

walac · 2018-04-30T11:23:58Z

Any news?

I am not the maintainer of PyUSB anymore, 303 @SimplicityGuy

roberthartung · 2018-07-19T06:03:01Z

Fixed another bug where userdata was pointing to the wrong object, if a dict was passed directly to the register function.

slide · 2019-01-18T20:25:12Z

Is there an example on how to use this in practice?

rautesamtr · 2019-10-07T15:10:05Z

The following example seems to work but also causes an exception

import usb.hotplug

def on_plug(dev, event, user_data):
    print(dev, event, user_data)

handle = usb.hotplug.register_callback(0x01 | 0x02, 0, -1, -1, -1, on_plug, None)

for event in usb.hotplug.loop():
    print(event)

Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 257, in 'converting callback result'
TypeError: an integer is required (got type NoneType)
Exception ignored in: <bound method _HotplugHandle.callback of <usb.backend.libusb1._HotplugHandle object at 0x7f676c5ab0d0>>

mcuee · 2019-11-25T02:29:25Z

Please help to rebase. Thanks.

jonasmalacofilho · 2019-11-29T14:48:05Z

Conflict was trivial. Solved it through the web UI, sorry for the resulting ugly merge commit.

Still needs to be tested, and possibly a fix for the issue mentioned by @raetiacorvus.

roberthartung · 2019-11-29T16:16:56Z

I will try to rebase and test tomorrow! I will force push to get rid of the merge commit as well.

om26er · 2019-12-23T21:22:25Z

Can one of the maintainers kindly take a look at the pull request and provide feedback. This is quite a useful feature that other libraries like https://github.com/python-escpos/python-escpos use to actively monitor connected usb printers.

om26er · 2019-12-23T21:33:02Z

usb/backend/libusb1.py

@@ -575,6 +582,16 @@ def libusb_fill_iso_transfer(_libusb_transfer_p, dev_handle, endpoint, buffer, l
    #int libusb_handle_events(libusb_context *ctx);
    lib.libusb_handle_events.argtypes = [c_void_p]

+    try:
+        lib.libusb_hotplug_register_callback.argtypes = [c_void_p, c_int, c_int, c_int, c_int, c_int, _libusb_hotplug_callback_fn, py_object, POINTER(_libusb_hotplug_callback_handle)]
+    except AttributeError:


Not really doing a review, just putting a comment: A mention about why exception handling was needed would be helpful

I have no idea. :-D

Looking at the code: I am not sure, the code existing code above mine also catched the exception - sometimes. Too bad I didn't document this. But I guess I just did the same way as the existing code.
Might have something to do with POINTER c_void_p? not sure.

In the other places it is used to deal with older versions libusb 1.0 that lack certain APIs.¹

All hotplug APIs are marked with

Since version 1.0.16, LIBUSB_API_VERSION >= 0x01000102

so the try-catch blocks are appropriate here.

¹ Though in some of these existing places it might not be necessary after all (e.g. libusb_get_port_number).

jonasmalacofilho · 2019-12-26T23:38:32Z

@om26er

It's on my queue, but there a few bugs ahead of it still.

I'm also hoping that @roberthartung can take a first look at the possible issue pointed out by @raetiacorvus, since right now he knows a lot more about USB hotplug than me.

…userdata was pointing to a wrong object

roberthartung · 2019-12-27T08:56:38Z

Force-pushed with latest rebase.

roberthartung · 2019-12-27T09:30:49Z

@jonasmalacofilho @raetiacorvus You code is just missing a line of code, it should be:

import usb.hotplug

def on_plug(dev, event, user_data):
    print(dev, event, user_data)
    return 0

handle = usb.hotplug.register_callback(0x01 | 0x02, 0, -1, -1, -1, on_plug, None)

for event in usb.hotplug.loop():
    print(event)

The callback function requires a return value ( see Documentation ):

bool whether this callback is finished processing events. returning 1 will cause this callback to be deregistered

jonasmalacofilho · 2020-02-16T09:28:04Z

Quick update: I started to look over this pull request, but there are some things I still don't quite understand (so no review yet).

I'm also thinking about whether the public API should be that tied to libusb1. Sure, libusb1 is the only backend that matters (in the foreseeable future); it's also hard to build a general API based on a single real world implementation. But maybe we could avoid depending/exposing/directly manipulating libusb1 constants, and also be a bit closer to find when it comes to specifying vendor/product/class filters. Again, not sure about this...

RyanHope · 2020-05-25T03:06:37Z

This need to become a higher priority.

roberthartung · 2020-05-25T06:37:19Z

Quick update: I started to look over this pull request, but there are some things I still don't quite understand (so no review yet).

I'm also thinking about whether the public API should be that tied to libusb1. Sure, libusb1 is the only backend that matters (in the foreseeable future); it's also hard to build a general API based on a single real world implementation. But maybe we could avoid depending/exposing/directly manipulating libusb1 constants, and also be a bit closer to find when it comes to specifying vendor/product/class filters. Again, not sure about this...

Hm yeah it makes sense I guess. I will try to implement some abstracted API or at least provide generalized constants!

giusebar · 2020-12-17T19:18:41Z

Has this been abandoned? would be a really useful feature

jonasmalacofilho

I think my previous comment still applies.

I'm also thinking about whether the public API should be that tied to libusb1. Sure, libusb1 is the only backend that matters (in the foreseeable future); it's also hard to build a general API based on a single real world implementation. But maybe we could avoid depending/exposing/directly manipulating libusb1 constants, and also be a bit closer to find when it comes to specifying vendor/product/class filters.

While this appears to be a functional implementation, we have the problem that the advertised goal of PyUSB still is "an API rich, backend neutral Python USB module easy to use." This is a bit weird in a time where, essentially, only libusb1 is maintained, but it may still be useful if new backends become available.

I honestly don't know how I feel about dropping the "backend neutral" requirement, nor do I think I should get to decide about that alone. For the time being, I think it's better to keep as much neutrality as possible, which in this case would mean at least exploring an API that leaks a lot less of the underlying libusb1 backend.

williamkapke · 2022-01-05T18:33:47Z

I extracted the changes from this PR in to a monkey patch. Seems to work great - but happy to hear about any troubles I may find doing this. Hope to see this PR get resolved someday! Thanks.

Patch

import usb
from usb.core import Device
from usb.backend.libusb1 import (
    CFUNCTYPE, POINTER, c_int, c_void_p, _libusb_device_handle, c_uint, py_object,
    _objfinalizer, byref, _Device
)

# # # # # #  PATCH pyusb for hotplug # # # # # #
# Extracted from: https://github.com/pyusb/pyusb/pull/160
backend = usb.backend.libusb1.get_backend()

_libusb_hotplug_callback_handle = c_int
_libusb_hotplug_callback_fn = CFUNCTYPE(c_int, c_void_p, _libusb_device_handle, c_uint, py_object)
backend.lib.libusb_hotplug_register_callback.argtypes = [
    c_void_p, c_int, c_int, c_int, c_int, c_int,
    _libusb_hotplug_callback_fn, py_object,
    POINTER(_libusb_hotplug_callback_handle)
]
backend.lib.libusb_hotplug_deregister_callback.argtypes = [
    c_void_p, _libusb_hotplug_callback_handle
]


class _HotplugHandle(_objfinalizer.AutoFinalizedObject):
    def __init__(self, backend, events, flags, vendor_id, product_id, dev_class, user_callback, user_data):
        self.user_callback = user_callback
        self.__callback = _libusb_hotplug_callback_fn(self.callback)
        self.__backend = backend
        # If an object is passed directly and never stored anywhere,
        # the pointer will remain and user data might be wrong!
        # therefore we have to keep a refernce here
        self.__user_data = py_object(user_data)
        handle = _libusb_hotplug_callback_handle()
        backend.lib.libusb_hotplug_register_callback(backend.ctx, events, flags, vendor_id, product_id, dev_class,
                                                     self.__callback, self.__user_data, byref(handle))

    def callback(self, ctx, dev, evnt, user_data):
        dev = Device(_Device(dev), self.__backend)
        return self.user_callback(dev, evnt, user_data)


def register_callback(callback, *,
                      user_data=None,
                      events=0x01 | 0x02,  # arrive and exit
                      flags=0,  # do not emumerate on register
                      vendor_id=-1,  # match any
                      product_id=-1,  # match any
                      dev_class=-1  # match any
                      ):
    return _HotplugHandle(backend, events, flags, vendor_id, product_id, dev_class, callback, user_data)


def deregister_callback(handle):
    backend.lib.libusb_hotplug_deregister_callback(backend.ctx, handle.handle)


def loop():
    while True:
        yield backend.lib.libusb_handle_events(backend.ctx)

Use

def on_plug(dev, event, user_data):
    print(dev, event, user_data)
    return 0

handle = register_callback(on_plug)

for event in loop():
    print(event)

NastuzziSamy · 2022-08-01T19:54:27Z

Thank you a lot @williamkapke, works like a sharm !

ChangmingTian · 2023-07-16T13:07:43Z

I extracted the changes from this PR in to a monkey patch. Seems to work great - but happy to hear about any troubles I may find doing this. Hope to see this PR get resolved someday! Thanks.

Patch

import usb
from usb.core import Device
from usb.backend.libusb1 import (
    CFUNCTYPE, POINTER, c_int, c_void_p, _libusb_device_handle, c_uint, py_object,
    _objfinalizer, byref, _Device
)

# # # # # #  PATCH pyusb for hotplug # # # # # #
# Extracted from: https://github.com/pyusb/pyusb/pull/160
backend = usb.backend.libusb1.get_backend()

_libusb_hotplug_callback_handle = c_int
_libusb_hotplug_callback_fn = CFUNCTYPE(c_int, c_void_p, _libusb_device_handle, c_uint, py_object)
backend.lib.libusb_hotplug_register_callback.argtypes = [
    c_void_p, c_int, c_int, c_int, c_int, c_int,
    _libusb_hotplug_callback_fn, py_object,
    POINTER(_libusb_hotplug_callback_handle)
]
backend.lib.libusb_hotplug_deregister_callback.argtypes = [
    c_void_p, _libusb_hotplug_callback_handle
]


class _HotplugHandle(_objfinalizer.AutoFinalizedObject):
    def __init__(self, backend, events, flags, vendor_id, product_id, dev_class, user_callback, user_data):
        self.user_callback = user_callback
        self.__callback = _libusb_hotplug_callback_fn(self.callback)
        self.__backend = backend
        # If an object is passed directly and never stored anywhere,
        # the pointer will remain and user data might be wrong!
        # therefore we have to keep a refernce here
        self.__user_data = py_object(user_data)
        handle = _libusb_hotplug_callback_handle()
        backend.lib.libusb_hotplug_register_callback(backend.ctx, events, flags, vendor_id, product_id, dev_class,
                                                     self.__callback, self.__user_data, byref(handle))

    def callback(self, ctx, dev, evnt, user_data):
        dev = Device(_Device(dev), self.__backend)
        return self.user_callback(dev, evnt, user_data)


def register_callback(callback, *,
                      user_data=None,
                      events=0x01 | 0x02,  # arrive and exit
                      flags=0,  # do not emumerate on register
                      vendor_id=-1,  # match any
                      product_id=-1,  # match any
                      dev_class=-1  # match any
                      ):
    return _HotplugHandle(backend, events, flags, vendor_id, product_id, dev_class, callback, user_data)


def deregister_callback(handle):
    backend.lib.libusb_hotplug_deregister_callback(backend.ctx, handle.handle)


def loop():
    while True:
        yield backend.lib.libusb_handle_events(backend.ctx)

Use

def on_plug(dev, event, user_data):
    print(dev, event, user_data)
    return 0

handle = register_callback(on_plug)

for event in loop():
    print(event)

handle = _libusb_hotplug_callback_handle() need change to self.handle = libusb_hotplug_callback_handle()
Must quite on_plug before call dev.ctrl_transfer API,Or get resource busy error

mcuee · 2024-04-07T02:21:23Z

FYI: there is a pending but working PR for libusb Windows hotplug implementation.

windows: hotplug implementation libusb/libusb#1406

walac force-pushed the master branch from eb72cbd to fd25318 Compare January 14, 2017 14:19

roberthartung mentioned this pull request Aug 11, 2017

Implement hotplug events #64

Open

om26er reviewed Dec 23, 2019

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roberthartung added 3 commits December 27, 2019 09:55

First implementation for libusb1 based hotplug

3c46bb9

hotplug: user_data was not handled correctly

16be259

fixes a bug when unplugging and pluggin in a device the second time: …

4ed0cd6

…userdata was pointing to a wrong object

roberthartung force-pushed the hotplug branch from f8380b6 to 4ed0cd6 Compare December 27, 2019 08:56

jonasmalacofilho self-requested a review December 28, 2019 08:21

jonasmalacofilho added this to the PyUSB 1.1.0 milestone Jan 10, 2020

jonasmalacofilho mentioned this pull request Sep 9, 2020

How to realize the function same as hotplugging #323

Closed

mcuee modified the milestones: PyUSB 1.1.0, PyUSB 1.2.0 Sep 16, 2020

mcuee added enhancement libusb1 labels Feb 1, 2021

RoyTrudell approved these changes Mar 24, 2021

View reviewed changes

mcuee modified the milestones: PyUSB 1.2.0, pyusb 1.3.0 Jun 15, 2021

jonasmalacofilho reviewed Jun 15, 2021

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ndim mentioned this pull request Jul 6, 2021

Port to FreeBSD to make socranop more portable in general socratools/socranop#27

Open

mcuee mentioned this pull request Jul 21, 2021

usb.core.USBError: [Errno 19] No such device (it may have been disconnected) #292

Closed

mcuee mentioned this pull request Aug 22, 2021

Confusing error reporting on hardware disconnect eblot/pyftdi#120

Open

jonasmalacofilho modified the milestones: PyUSB 1.3.0, PyUSB 1.4.0 Apr 8, 2022

nkarstens mentioned this pull request Jan 11, 2024

USB support should better handle the cable being disconnected pybricks/pybricksdev#70

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Fixes #64 - First implementation for libusb1-based hotplug #160

Fixes #64 - First implementation for libusb1-based hotplug #160

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Patch

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mcuee commented Apr 7, 2024

Fixes #64 - First implementation for libusb1-based hotplug #160

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Fixes #64 - First implementation for libusb1-based hotplug #160

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