Prepare for an async scan
struct async_scan_data * scsi_prep_async_scan(struct Scsi_Host * shost);
shost
the host which will be scanned
a cookie to be passed to scsi_finish_async_scan
Tells the midlayer this host is going to do an asynchronous scan. It reserves the host's position in the scanning list and ensures that other asynchronous scans started after this one won't affect the ordering of the discovered devices.