1ATA_SLAVE_LINK_INIT(9)          libata Library          ATA_SLAVE_LINK_INIT(9)
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NAME

6       ata_slave_link_init - initialize slave link
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SYNOPSIS

9       int ata_slave_link_init(struct ata_port * ap);
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ARGUMENTS

12       ap
13           port to initialize slave link for
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DESCRIPTION

16       Create and initialize slave link for ap. This enables slave link
17       handling on the port.
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19       In libata, a port contains links and a link contains devices. There is
20       single host link but if a PMP is attached to it, there can be multiple
21       fan-out links. On SATA, there's usually a single device connected to a
22       link but PATA and SATA controllers emulating TF based interface can
23       have two - master and slave.
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25       However, there are a few controllers which don't fit into this
26       abstraction too well - SATA controllers which emulate TF interface with
27       both master and slave devices but also have separate SCR register sets
28       for each device. These controllers need separate links for physical
29       link handling (e.g. onlineness, link speed) but should be treated like
30       a traditional M/S controller for everything else (e.g. command issue,
31       softreset).
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33       slave_link is libata's way of handling this class of controllers
34       without impacting core layer too much. For anything other than physical
35       link handling, the default host link is used for both master and slave.
36       For physical link handling, separate ap->slave_link is used. All dirty
37       details are implemented inside libata core layer. From LLD's POV, the
38       only difference is that prereset, hardreset and postreset are called
39       once more for the slave link, so the reset sequence looks like the
40       following.
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42       prereset(M) -> prereset(S) -> hardreset(M) -> hardreset(S) ->
43       softreset(M) -> postreset(M) -> postreset(S)
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45       Note that softreset is called only for the master. Softreset resets
46       both M/S by definition, so SRST on master should handle both (the
47       standard method will work just fine).
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LOCKING

50       Should be called before host is registered.
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RETURNS

53       0 on success, -errno on failure.
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AUTHOR

56       Jeff Garzik
57           Author.
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60Kernel Hackers Manual 3.10         June 2019            ATA_SLAVE_LINK_INIT(9)
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