ATA_SLAVE_LINK_INIT(9)						  libata Library					    ATA_SLAVE_LINK_INIT(9)

NAME

       ata_slave_link_init - initialize slave link

SYNOPSIS

       int ata_slave_link_init(struct ata_port * ap);

ARGUMENTS

       ap
	   port to initialize slave link for

DESCRIPTION

       Create and initialize slave link for ap. This enables slave link handling on the port.

       In libata, a port contains links and a link contains devices. There is single host link but if a PMP is attached to it, there can be
       multiple fan-out links. On SATA, there's usually a single device connected to a link but PATA and SATA controllers emulating TF based
       interface can have two - master and slave.

       However, there are a few controllers which don't fit into this abstraction too well - SATA controllers which emulate TF interface with both
       master and slave devices but also have separate SCR register sets for each device. These controllers need separate links for physical link
       handling (e.g. onlineness, link speed) but should be treated like a traditional M/S controller for everything else (e.g. command issue,
       softreset).

       slave_link is libata's way of handling this class of controllers without impacting core layer too much. For anything other than physical
       link handling, the default host link is used for both master and slave. For physical link handling, separate ap->slave_link is used. All
       dirty details are implemented inside libata core layer. From LLD's POV, the only difference is that prereset, hardreset and postreset are
       called once more for the slave link, so the reset sequence looks like the following.

       prereset(M) -> prereset(S) -> hardreset(M) -> hardreset(S) -> softreset(M) -> postreset(M) -> postreset(S)

       Note that softreset is called only for the master. Softreset resets both M/S by definition, so SRST on master should handle both (the
       standard method will work just fine).

LOCKING

       Should be called before host is registered.

RETURNS

       0 on success, -errno on failure.

AUTHOR

       Jeff Garzik
	   Author.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010						    ATA_SLAVE_LINK_INIT(9)