libusb-devel

[Libusb-devel] claim interface fails when claimed by usbhid driver

[Brian N. <br...@tw...>]

Still having the same issues, here's a little more detail:

I'm running a recent Linux 2.6 kernel.  I have a HID device, shows up as 
a joystick (which it should).  I need to send a short two-byte control 
message to the device for configuration.

The problem I'm having is the usb_claim_interface call fails because 
it's already claimed by the usbhid driver.  I can disconnect it from the 
driver and the code works fine, but that's not what I want to do, 
because I want to maintain the joystick functionality that I already have.

I've attached my code and the output from it below.  Is this going to be 
possible?  Do I need to investigate other methods of communicating with 
the device, like hiddev or perhaps something on an even lower level?  I 
haven't done a ton of research, but I understand it might be possible to 
write to the device directly thorough the /proc/bus/usb/XXX/YYY file?

This process works fine under Windows, so I'm not sure where to go from 
here under Linux.  Thanks for any suggestions that anyone can offer.

-Brian

Program output (as root):

usb_set_debug: Setting debugging level to 8 (on)
usb_os_find_busses: Found 004
usb_os_find_busses: Found 003
usb_os_find_busses: Found 002
usb_os_find_busses: Found 001
usb_os_find_busses: Skipping non bus directory devices
usb_os_find_devices: Found 001 on 004
usb_os_find_devices: Found 001 on 003
usb_os_find_devices: Found 001 on 002
usb_os_find_devices: Found 002 on 001
skipped 1 class/vendor specific interface descriptors
usb_os_find_devices: Found 001 on 001
Check that you have permissions to write to 001/002 and, if you don't, 
that you set up hotplug (http://linux-hotplug.sourceforge.net/) correctly.
USB error: could not claim interface 0: Device or resource busy
USB error: error sending control message: Device or resource busy
usb_claim_interface error: could not claim interface 0: Device or 
resource busy
msg return: -16 | error sending control message: Device or resource busy

The code:

#include <usb.h>

int main(void)
{
  struct usb_bus *busses;
  struct usb_bus *bus;
  struct usb_device *dev;
  usb_dev_handle *usb_handle;

  int ret;
  unsigned char command[2] = {0xCC, 0x03};

  usb_init();
  usb_set_debug(8);
  usb_find_busses();
  usb_find_devices();

  busses = usb_get_busses();

  for (bus = busses; bus; bus = bus->next)
  {
      for (dev = bus->devices; dev; dev = dev->next)
      {
          if (dev->descriptor.idVendor == 0xFAFA)
          {
              usb_handle = usb_open(dev);
              if(usb_handle)
              {
                  if (usb_set_configuration(usb_handle, 
dev->config->bConfigurationValue))
                  {
                      printf("usb_set_configuration error: %s\n", 
usb_strerror());
                  }

                  usb_set_altinterface(usb_handle, 0);

                  if (usb_claim_interface(usb_handle, 0) < 0)
                  {
                      printf("usb_claim_interface error: %s\n", 
usb_strerror());
                  }

                  ret = usb_control_msg(usb_handle,
                          0x21,    // Set_Report request (page 52 HID Spec)
                          0x09,    // SET_REPORT (Top Remarks page 51)
                          0x200,    // (Bottom Remarks section page 51)
                          0x00,    // Interface 0
                          command,    // Buffer for characters to transmit
                          0x02,    // Size of message
                          10);     // Milliseconds of timeout

                  printf("msg return: %d | %s\n", ret, ret < 0 ? 
usb_strerror() : "<no error>");

                  usb_close(usb_handle);
              }
              else
              {
                  printf("Error opening device.\n");
              }
          }
      }
  }
}

Re: [Libusb-devel] claim interface fails when claimed by usbhid driver

[Charles L. <cl...@gm...>]

On 5/22/05, Brian Nelson <br...@tw...> wrote:
> The problem I'm having is the usb_claim_interface call fails because
> it's already claimed by the usbhid driver.  I can disconnect it from the
> driver and the code works fine, but that's not what I want to do,
> because I want to maintain the joystick functionality that I already have=
.

Unfortunately, while the kernel provides a "detach driver" call, it
does not offer a corresponding "reattach driver" call.

There are a couple of hooks in the kernel HID driver to handle odd
devices, but your situation might require a nontrivial patch.

The other option is to "fly blind" and just issue your command without
claiming the interface. The kernel should queue your control message
such that it will not be mixed up with other control message/response
pairs from the HID driver, but there are no guarantees with that
method.

--=20
- Charles Lepple

Re: [Libusb-devel] claim interface fails when claimed by usbhid driver

[Brian N. <br...@tw...>]

Charles Lepple wrote:

>On 5/22/05, Brian Nelson <br...@tw...> wrote:
>  
>
>>The problem I'm having is the usb_claim_interface call fails because
>>it's already claimed by the usbhid driver.  I can disconnect it from the
>>driver and the code works fine, but that's not what I want to do,
>>because I want to maintain the joystick functionality that I already have.
>>    
>>
>
>Unfortunately, while the kernel provides a "detach driver" call, it
>does not offer a corresponding "reattach driver" call.
>
>There are a couple of hooks in the kernel HID driver to handle odd
>devices, but your situation might require a nontrivial patch.
>
>The other option is to "fly blind" and just issue your command without
>claiming the interface. The kernel should queue your control message
>such that it will not be mixed up with other control message/response
>pairs from the HID driver, but there are no guarantees with that
>method.
>
>  
>
By "flying blind," are you saying I should try just calling 
usb_control_msg without calling usb_claim_interface first?  I think I've 
done that, and usb_control_msg just returns an error.

If you're not talking about that (perhaps something outside of libusb?), 
can you give me a pointer in the right direction?

Thanks!
-Brian

Re: [Libusb-devel] claim interface fails when claimed by usbhid driver

[Charles L. <cl...@gm...>]

On 5/23/05, Brian Nelson <br...@tw...> wrote:
> Charles Lepple wrote:
>=20
[...]
> >The other option is to "fly blind" and just issue your command without
> >claiming the interface. The kernel should queue your control message
> >such that it will not be mixed up with other control message/response
> >pairs from the HID driver, but there are no guarantees with that
> >method.
> >
> >
> >
> By "flying blind," are you saying I should try just calling
> usb_control_msg without calling usb_claim_interface first?

yes

>  I think I've done that, and usb_control_msg just returns an error.

I thought you could get away with that in Linux, but maybe it's only on OS =
X.

--=20
- Charles Lepple