Man page 9 : usb_control_msg

usb_control_msg - Builds a control urb, sends it off and waits for completion

int usb_control_msg(struct usb_device *  dev , unsigned int  pipe , __u8  request , __u8  requesttype , __u16  value , __u16  index , void *  data , __u16  size , int  timeout );

dev
    pointer to the usb device to send the message to

pipe
    endpoint « pipe » to send the message to

request
    USB message request value

requesttype
    USB message request type value

value
    USB message value

index
    USB message index value

data
    pointer to the data to send

size
    length in bytes of the data to send

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

!in_interrupt ()

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

If successful, it returns the number of bytes transferred, otherwise a negative error number.

DonAqt 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 donAqt have a handle on the URB used, you canAqt cancel the request.