Getting overlap when using sg ioctl calls
 

I'm looking at this site: http://www.tldp.org/HOWTO/SCSI-Generic-HOWTO/open.html

It says the open can specify O_NONBLOCK. But it does not say how to get control when the operation has finished. Normally one would get a callback. Is that by some chance the 3rd argument in the ioctl?

Eddy