[libhid-discuss] hid_force_open failed with return code 12

[Charles Lepple]

Marius Scurtescu wrote:
> On 3/21/07, Charles Lepple <clepple at ghz.cc> wrote:
>> Marius Scurtescu wrote:
>> > On 3/21/07, Charles Lepple <clepple at ghz.cc> wrote:
>> >> On Mar 20, 2007, at 10:34 PM, Marius Scurtescu wrote:
>> >>
>> >> > Hi,
>> >> >
>> >> > I am using libhid under Ubuntu Edgy, tried both i386 and amd64
>> >> > (0.2.15+20060325-2ubuntu1).
>> >> >
>> >> > Trying to access a Radio Shark 2 device. The problem is that libhid
>> >> > cannot detach the kernel driver from the USB device.
>> >> >
>> >> > Using libhid-detach-device, same thing.
>> >> >
>> >> > Any suggestions?
>> >>
>> >> The most common problem is not having write permission to the device
>> >> node in /dev/bus/usb/*/*.
>> >
>> > That must be it. If I am running as root then it detaches fine. Only
>> > root has write access to these devices. How can I change this? Should
>> > I change the group or force write for all?
>> >
>> > Also, the device gets created when you insert the USB connector, can
>> > you control permissions on that?
>>
>> You can do something like what we have in Network UPS Tools for USB
>> UPSes:
>>
>> http://boxster.ghz.cc/projects/nut/browser/trunk/scripts/udev/nut-usbups.rules.in
>>
>> I think the README file one level up has some info on installing the
>> udev
>> rules file. (Note that the autoconf script would take the
>> nut-usbups.rules.in file and replace @RUN_AS_GROUP@ with the actual
>> configured group, writing the output to nut-usbups.rules. Your udev
>> script
>> could do something similar with your userid instead of the group.)
>
> Thanks for the suggestion. I will look into this.

OK. Don't let the apparent complexity of the file scare you - it's only
that big because we are trying to support a large number of USB UPS
models.

-- 
Charles Lepple