ahci/sili.4 - Document sysctl nodes & loader tunables

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.\"	$OpenBSD: ahci.4,v 1.7 2008/04/19 01:18:39 djm Exp $
.\"
.\" Copyright (c) 2006 David Gwynne <dlg@openbsd.org>
.\"
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd August 3, 2009
.Dt AHCI 4
.Os
.Sh NAME
.Nm ahci
.Nd Advanced Host Controller Interface for Serial ATA
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device ahci"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
ahci_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for Serial ATA controllers conforming to the
Advanced Host Controller Interface specification.
.Pp
Several AHCI capable controllers also provide a compatibility mode that
causes them to appear as a traditional ATA controller supported by
.Xr nata 4 .
.Pp
Although
.Nm
controllers are actual ATA controllers, the driver emulates SCSI via a
translation layer.
.Sh LOADER TUNABLES
The following hints may be set in
.Xr loader.conf 5
to control the
.Nm
driver's behavior.
Note that the hint need only exist, so removing it requires commenting it out.
.Pp
Usually both the
.Xr nata 4
and the
.Nm
drivers are loaded.
The
.Xr nata 4
driver will pick up any ata-like devices which the
.Nm
driver misses.
If the
.Nm
driver is disabled the
.Xr nata 4
driver will typically pick up the
.Nm
devices, albeit under the
.Pa ad
disk name rather than the
.Pa da
disk name.
.Bd -literal -offset indent
hint.ahci.disabled=1
.Ed
.Pp
The
.Nm
driver can be told to force a lower-speed 1.5Gb link speed
if necessary, and can also be told to refrain from attempting to send
certain higher-level ATA commands to initialize ATA features which
some devices might not properly implement.
.Bd -literal -offset indent
hint.ahci.force150=1
hint.ahci.nofeatures=1
.Ed
.Sh SYSCTL VARIABLES
Link power management can be set with the sysctl
.Va hw.ahci%d.%d.link_pwr_mgmt
to 0 for `disabled', 1 for `medium', and 2 for `aggressive'.
Link power state can be read with the sysctl
.Va hw.ahci%d.%d.link_pwr_state .
.Sh SEE ALSO
.Xr intro 4 ,
.Xr nata 4 ,
.Xr pci 4 ,
.Xr scsi 4 ,
.Xr sili 4 ,
.Xr loader.conf 5
.Sh HISTORY
The
.Nm
driver first appeared in
.Dx 2.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was originally written by
.An David Gwynne Aq dlg@openbsd.org
and
.An Christopher Pascoe Aq pascoe@openbsd.org
for
.Ox .
.Pp
It was ported to
.Dx
by
.An Matt Dillon Aq dillon@apollo.backplane.com
who added new features such as hot-plug and port multiplier support.