Problem with libusb20_dev_get_port_path()

[Uffe Jakobsen]

On 2015-01-20 22:44, Hans Petter Selasky wrote:
> On 01/20/15 20:48, Uffe Jakobsen wrote:
>>
>> On 2015-01-20 12:45, Hans Petter Selasky wrote:
>>>
>>> It appears there is a minor bug in the kernel regarding this field. See
>>> below:
>>>
>>> https://svnweb.freebsd.org/changeset/base/277417
>>>
>>> Should work now.
>>>
>>
>> Thanks for the quick response and fix
>>
>> How far back does the problem reach ?
>>
>>
>
>
> I think the IOCTL never worked except returning no path (0) like you
> observed.
>

Ok, thanks

Another observation around the cross-platform use of 
libusb20_dev_get_port_path() and libusb_get_port_numbers():

On FreeBSD it seems that one needs to perform the respective usb open 
calls for the device before the two calls above succeeds without an 
negative error code.

Whereas the usb open calls does not seem to be needed with the linux 
impl of libusb.

Different behaviour between libusb on FreeBSD and linux creates a 
compatibility problems where linux-maintained programs accessing 
libusb20_dev_get_port_path() and libusb_get_port_numbers() will fail on 
FreeBSD but works on linux. (I've just spent some hours with such 
program) :-)

I've looked through the available documentation without finding anything 
substantial - and hence I do not know which one is "right".

/Uffe