usb_bulk_msg return value -8

random0 · 11-05-2009, 05:09 PM

I'm writing a USB kernel driver and for some of the bulk transfers, I'm using the following function.

Code:

#include <linux/usb.h>
int usb_bulk_msg (struct usb_device * usb_dev, unsigned int pipe, void * data, int len, int * actual_length, int timeout);

When I call it, it returns -8. The man page states:

Quote:

If successful, it returns 0, otherwise a negative error number. The number of actual bytes transferred will be placed in the actual_timeout parameter.

If by "negative error number" it is referring to a value defined in errno.h, then that return value means "Exec format error". usb_bulk_msg is in the kernel, it shouldn't be calling exec. And if it was, wth?

Any ideas on what this value actually means?

ammorais · 11-05-2009, 05:34 PM

I believe you will actually look in to the source code. BTW, why do you think that is returning a value defined in "errno.h"? It just returns an int It can be anything.

Looking in to the source code you have:

Code:

return usb_start_wait_urb(urb,timeout,actual_length);

Fallowing usb_start_wait_urb I discovered:

Code:

ret = usb_internal_control_msg(dev, pipe, dr, data, size, timeout);

I don't think it has anything to do with errno.h