[libhid-discuss] Question about hid_force_open failed

[Charles Lepple]

On Aug 20, 2014, at 11:07 AM, Shen Chuan <shen at minutekey.com> wrote:

> Hello, 
> 
> Just installed libhid in the opensuse platform and running a c program to communicate with the card reader
> 
> i | libhidapi-devel   | Development libraries and header files for hidapi                   | package
> i | libhidapi-hidraw0 | Simple library for communicating with USB and Bluetooth HID devices | package
> i | libhidapi-libusb0 | Simple library for communicating with USB and Bluetooth HID devices | package
> 
> But when I run it, it always give me 13 error code. Not sure what it means, is there somewhere I can debug it?

You could try running it under strace to see the return values from the system calls. If the 13 is coming from a system call, strace will show the symbolic error name.

> hid_force_open failed with return code 13

There are at least three separate HID APIs for Linux:

1) http://libhid.alioth.debian.org/ (defunct; uses this list)
2) the Linux kernel HID API, sometimes called hidraw
3) http://www.signal11.us/oss/hidapi/ (also https://github.com/signal11/hidapi) which corresponds to those packages

I am not too familiar with #2 and #3. If it is #3, you should be able to look up that error code in their Doxygen output: http://www.signal11.us/oss/hidapi/hidapi/doxygen/html/group__API.html

If it is #2, error 13 is EACCESS, so you might want to check permissions on /dev/bus/usb. HIDAPI might also be passing that error code through to you from the kernel HID API.


-- 
Charles Lepple
clepple at gmail



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