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linuxusblibusb

Porting windows USB HID code to libusb

I'm trying to port some windows code that uses HidD_GetInputReport to linux using libusb. From what I can tell I need to make a call to usb_control_msg but I'm having problems figuring out what parameters to pass in.

The report id I'm after is 0x01. Here is what I have so far.

#define HID_GET_REPORT  0x01
#define HID_REPORT_TYPE_INPUT  0x01
#define INTERFACE_NUMBER 0x00

int reportId = 0x01;
int bytesSent = usb_control_msg(
  devHandle,
  USB_ENDPOINT_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
  HID_GET_REPORT,
  (HID_REPORT_TYPE_INPUT << 8) | reportId,
  INTERFACE_NUMBER,
  buf,
  sizeof(buf),
  10000);

I'm really not sure about HID_GET_REPORT, HID_REPORT_TYPE_INPUT, and INTERFACE_NUMBER. I found them in an example on the web. Changing the various values does result in different return codes but those don't appear to be documented anywhere either.

Solution

  • Looks like you need to detach the kernel and claim the interface before calling other functions. I made calls to the following and it fixed the problem.

    usb_detach_kernel_driver_np
usb_claim_interface