ata_qc_issue_prot — issue taskfile to device in proto-dependent manner
command to issue to device
Using various libata functions and hooks, this function starts an ATA command. ATA commands are grouped into classes called “protocols”, and issuing each type of protocol is slightly different.
May be used as the qc_issue entry in ata_port_operations.
spin_lock_irqsave(host lock)
Zero on success, AC_ERR_* mask on failure