sata_scr_read — read SCR register of the specified port
ATA link to read SCR for
SCR to read
Place to store read value
Read SCR register reg of link into *val. This function is guaranteed to succeed if link is ap->link, the cable type of the port is SATA and the port implements ->scr_read.
None if link is ap->link. Kernel thread context otherwise.
0 on success, negative errno on failure.