ata_std_prereset — prepare for reset
ATA port to be reset
deadline jiffies for the operation
ap is about to be reset. Initialize it. Failure from prereset makes libata abort whole reset sequence and give up that port, so prereset should be best-effort. It does its best to prepare for reset sequence but if things go wrong, it should just whine, not fail.
Kernel thread context (may sleep)
0 on success, -errno otherwise.