Re: [libusb] Correct use of libusb with composite device

[RisingEdgeIndustries <su...@ri...>]

So I'm taking the same approach I take when I had these interfaces running
as stand alone devices.  My process is below.


Call get_device_list()
Loop through device list to find VID/PID
Once found open_device() with my VID/PID
[at this point I get string descriptors and max_packet_size() which works
fin]
I then execute claim_interface() for my device

I can claim interface 0, but when I try interface 1 I get the following
error:
ERROR: failed to claim interface, ret val = -12
ERROR: code - b'Operation not supported or unimplemented on this platform'

I know from the descriptors during enumeration my second interface is my
bulk interface with bInterfaceNumber "1".

I see both interfaces with correct VID/PID in device manager with correct
drivers and no icons indicating a problem.  Is there something obvious I'm
missing in this process?  This process works fine for non-composite HID
only or bulk only.


*Descriptor data:*


----- Device Descriptor -----
12 bLength
01 bDesc Type
00 02 bcdUSB (LSB, MSB)
00 bDeviceClass
00 bDeviceSubClass
00 bDeviceProtocol
40 bMaxPacketSize0 - Maximum packet size for Endpoint zero (only 8, 16, 32,
or 64 are valid).
BF 1C idVendor (LSB, MSB)
07 00 idProduct (LSB, MSB)
00 01 bcdDevice (BCD) (LSB, MSB)
01 iManufacturer (string index)
02 iProduct (string index)
03 iSerialNumber (string index)
01 bNumConfigurations (string index)

----- Configuration Descriptor -----
09 bLength
02 bDesc Type
40 00 wTotalLen  (LSB, MSB)
02 bNumInterfaces
01 bConfigurationValue
00 iConfiguration
80 bmAttributes
7D bmAttributes

----- Interface Descriptor -----
09 bLength
04 bDesc Type
00 bInterfaceNumber
00 bAlternateSetting
02 bNumEndpoints
03 bInterfaceClass
00 bInterfaceClass
00 bInterfaceProtocol
00 iInterface

----- HID Class Descriptor -----
09 bLength
21 bDesc Type
00 02 bcdHID (Hid Spec Release Number) (LSB, MSB)
00 bCountryCode (Country code (0x00 for not supported))
01 bNumDescriptors (Number of class descriptors)
22 bDescriptorType (Report descriptor type)
20 00 bDescriptorLength (Report descriptor type) (LSB, MSB)

----- Endpoint Descriptor -----
07 bLength
05 bDesc Type
81 bEndpointAddress
03 bmAttributes
40 00 wMaxPacketSize (LSB, MSB)
01 bInterval

----- Endpoint Descriptor -----
07 bLength
05 bDesc Type
01 bEndpointAddress
03 bmAttributes
40 00 wMaxPacketSize (LSB, MSB)
01 bInterval

----- Interface Descriptor -----
09 bLength
04 bDesc Type
01 bInterfaceNumber
00 bAlternateSetting
02 bNumEndpoints
FF bInterfaceClass
00 bInterfaceClass
00 bInterfaceProtocol
00 iInterface

----- Endpoint Descriptor -----
07 bLength
05 bDesc Type
82 bEndpointAddress
02 bmAttributes
40 00 wMaxPacketSize (LSB, MSB)
00 bInterval

----- Endpoint Descriptor -----
07 bLength
05 bDesc Type
02 bEndpointAddress
02 bmAttributes
40 00 wMaxPacketSize (LSB, MSB)
00 bInterval




On Wed, Jul 12, 2023 at 8:35 PM Xiaofan Chen <xia...@gm...> wrote:

> There is no limitation for your use case. Open the device normally and
> claim the
> correct interface (interface 1 in your case).
>
>  libusb_detach_kernel_driver() is not supported under Windows so it is
> not relevant.
>
> The limitations are mainly with things like IAD and CDC-ACM, not your use
> case.
> 1) https://github.com/libusb/libusb/pull/965 (PR merged, it will be in
> future 1.0.27 release)
> 2) https://github.com/libusb/libusb/issues/1238
>
> Best regards,
> Xiaofan
>
>
> On Thu, Jul 13, 2023 at 9:16 AM RisingEdgeIndustries
> <su...@ri...> wrote:
> >
> > Hello,
> >
> > I've been reading quite a bit of posts online about libusb and composite
> devices and the challenge due to windows assigning usbccgp.sys which acts
> as a "parent" driver with the individual interfaces appearing as separate
> devices.  I have a basic example to better understand libusb1.0 consisting
> of the following:
> >
> > USB Composite device -- default windows usbccgp.sys driver
> >     Interface 0 - HID interface with Windows HID driver auto loaded
> >     Interface 1 - custom bulk interface with WINUSB driver
> >
> > I've managed to get my descriptors straightened out to auto load the
> drivers I need and I assumed I could just use libusb's claim_interface()
> call to choose between my HID or bulk interface.  I now see that (I think)
> this is not the intended use because the parent driver seems to cause
> problems.  So I'm wondering if someone could clarify the correct approach
> to connect and transfer data for a composite device on Windows 10 in this
> situation with two interfaces.
> >
> > 1. What is the intended implementation in a situation like this?
> > 2. Since both the HID and bulk interfaces show up as devices (in
> windows) with the same VID/PID how should one connect to a specific one?
> Is claim_interface() the correct approach?
> > 3. I read that some people use libusb_detach_kernel_driver() but that is
> only for linux from what I see in the documentation - is that correct
> currently?  Just ask because I saw quite a few posts about this.
> >
> > I have both interfaces working as standalone projects so I think I'm
> pretty close, but the composite case isn't as straightforward as I thought.
> >
> > Thank you for the support and libusb!
> >
> > _______________________________________________
> > libusb-devel mailing list
> > lib...@li...
> > https://lists.sourceforge.net/lists/listinfo/libusb-devel
>