How to do response/request URB interrupt in libusb? - c

Question

I'm trying to replicate a Windows program on Linux. The program talks to the USB device.
Now I'm stuck on the part where the device sends URB_interrupt IN first, and the host answers. The capture looks like this (and this is the result I want to have):
Frame 29: 72 bytes on wire (576 bits), 72 bytes captured (576 bits) on interface usbmon0, id 0
USB URB
[Source: 1.16.2]
[Destination: host]
URB id: 0xffff8d92d4ece840
URB type: URB_COMPLETE ('C')
URB transfer type: URB_INTERRUPT (0x01)
Endpoint: 0x82, Direction: IN
Device: 16
URB bus id: 1
Device setup request: not relevant ('-')
Data: present (0)
URB sec: 1664781571
URB usec: 862138
URB status: Success (0)
URB length [bytes]: 8
Data length [bytes]: 8
[bInterfaceClass: Unknown (0xffff)]
Unused Setup Header
Interval: 8
Start frame: 0
Copy of Transfer Flags: 0x00000200, Dir IN
Number of ISO descriptors: 0
Leftover Capture Data: 0508ff0000000000
Frame 30: 64 bytes on wire (512 bits), 64 bytes captured (512 bits) on interface usbmon0, id 0
USB URB
[Source: host]
[Destination: 1.16.2]
URB id: 0xffff8d9321011cc0
URB type: URB_SUBMIT ('S')
URB transfer type: URB_INTERRUPT (0x01)
Endpoint: 0x82, Direction: IN
Device: 16
URB bus id: 1
Device setup request: not relevant ('-')
Data: not present ('<')
URB sec: 1664781571
URB usec: 865989
URB status: Operation now in progress (-EINPROGRESS) (-115)
URB length [bytes]: 8
Data length [bytes]: 0
[bInterfaceClass: Unknown (0xffff)]
Unused Setup Header
Interval: 8
Start frame: 0
Copy of Transfer Flags: 0x00000200, Dir IN
Number of ISO descriptors: 0
It looks like the device sends the answer first (URB type is 'URB_COMPLETE'), and after that, the host answers ('URB_SUBMIT'). Previously I have only encountered the opposite situation (i. e. swap order of the captured packets) and I know how to do it, but I have no idea how to do the upper-mentioned one.
I do the URB interrupt by the following function:
#define INTR_EP_IN 0x82
#define INTR_LENGTH 8
typedef unsigned char byte_t;
/* Proper opening, kernel detaching, and interface claiming... */
static int send_interrupt(libusb_device_handle *handle)
{
byte_t *packet;
int transferred = 0;
short sent;
packet = calloc(INTR_LENGTH, 1);
sent = libusb_interrupt_transfer(handle, INTR_EP_IN, packet, INTR_LENGTH,
&transferred, 10);
free(packet);
/* Note: always TIMEOUT_ERROR, but the packet gets captured anyway */
/*
if(sent != 0)
fprintf(stderr, INTRRPT_ERR_MSG, libusb_strerror(sent));
*/
return sent;
}
I've tried to change libusb_interrupt_transfer parameters, but nothing gave me the desired result.
Every time I get something like the following:
Frame 30: 64 bytes on wire (512 bits), 64 bytes captured (512 bits) on interface usbmon0, id 0
USB URB
[Source: host]
[Destination: 1.6.2]
URB id: 0xffff922c3bd69540
URB type: URB_SUBMIT ('S')
URB transfer type: URB_INTERRUPT (0x01)
Endpoint: 0x82, Direction: IN
Device: 6
URB bus id: 1
Device setup request: not relevant ('-')
Data: not present ('<')
URB sec: 1668092600
URB usec: 503008
URB status: Operation now in progress (-EINPROGRESS) (-115)
URB length [bytes]: 8
Data length [bytes]: 0
[Response in: 31]
[bInterfaceClass: Unknown (0xffff)]
Unused Setup Header
Interval: 8
Start frame: 0
Copy of Transfer Flags: 0x00000200, Dir IN
Number of ISO descriptors: 0
Frame 31: 64 bytes on wire (512 bits), 64 bytes captured (512 bits) on interface usbmon0, id 0
USB URB
[Source: 1.6.2]
[Destination: host]
URB id: 0xffff922c3bd69540
URB type: URB_COMPLETE ('C')
URB transfer type: URB_INTERRUPT (0x01)
Endpoint: 0x82, Direction: IN
Device: 6
URB bus id: 1
Device setup request: not relevant ('-')
Data: present (0)
URB sec: 1668092600
URB usec: 506108
URB status: No such file or directory (-ENOENT) (-2)
URB length [bytes]: 0
Data length [bytes]: 0
[Request in: 30]
[Time from request: 0.003100000 seconds]
[bInterfaceClass: Unknown (0xffff)]
Unused Setup Header
Interval: 8
Start frame: 0
Copy of Transfer Flags: 0x00000200, Dir IN
Number of ISO descriptors: 0
Which totally isn't what I intend to have.
I'm assuming I don't know something as I am not an expert in the USB protocol. There's also a chance that libusb just doesn't allow to do such transfer. In this case, I should do this via corresponding syscalls, but this is the last resort for me.