centos man page for usb_bulk_msg

USB_BULK_MSG(9) 						   USB Core APIs						   USB_BULK_MSG(9)

NAME
       usb_bulk_msg - Builds a bulk urb, sends it off and waits for completion

SYNOPSIS
       int usb_bulk_msg(struct usb_device * usb_dev, unsigned int pipe, void * data, int len, int * actual_length, int timeout);

ARGUMENTS
       usb_dev
	   pointer to the usb device to send the message to

       pipe
	   endpoint "pipe" to send the message to

       data
	   pointer to the data to send

       len
	   length in bytes of the data to send

       actual_length
	   pointer to a location to put the actual length transferred in bytes

       timeout
	   time in msecs to wait for the message to complete before timing out (if 0 the wait is forever)

CONTEXT
       !in_interrupt ()

DESCRIPTION
       This function sends a simple bulk message to a specified endpoint and waits for the message to complete, or timeout.

       Don't use this function from within an interrupt context, like a bottom half handler. If you need an asynchronous message, or need to send
       a message from within interrupt context, use usb_submit_urb If a thread in your driver uses this call, make sure your disconnect method can
       wait for it to complete. Since you don't have a handle on the URB used, you can't cancel the request.

       Because there is no usb_interrupt_msg and no USBDEVFS_INTERRUPT ioctl, users are forced to abuse this routine by using it to submit URBs
       for interrupt endpoints. We will take the liberty of creating an interrupt URB (with the default interval) if the target is an interrupt
       endpoint.

RETURN
       If successful, 0. Otherwise a negative error number. The number of actual bytes transferred will be stored in the actual_length paramater.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							   USB_BULK_MSG(9)