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	1	.\" $OpenBSD: ahci.4,v 1.7 2008/04/19 01:18:39 djm Exp $
	2	.\"
	3	.\" Copyright (c) 2006 David Gwynne <dlg@openbsd.org>
	4	.\"
	5	.\" Permission to use, copy, modify, and distribute this software for any
	6	.\" purpose with or without fee is hereby granted, provided that the above
	7	.\" copyright notice and this permission notice appear in all copies.
	8	.\"
	9	.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	10	.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	11	.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	12	.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	13	.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	14	.\" TORTIOUS ACTION, ARISING OUT OF
	15	.\" PERFORMANCE OF THIS SOFTWARE.
	16	.\"
	17	.Dd August 3, 2009
	18	.Dt AHCI 4
	19	.Os
	20	.Sh NAME
	21	.Nm ahci
	22	.Nd Advanced Host Controller Interface for Serial ATA
	23	.Sh SYNOPSIS
	24	To compile this driver into the kernel,
	25	place the following line in your
	26	kernel configuration file:
	27	.Bd -ragged -offset indent
	28	.Cd "device ahci"
	29	.Ed
	30	.Pp
	31	Alternatively, to load the driver as a
	32	module at boot time, place the following line in
	33	.Xr loader.conf 5 :
	34	.Bd -literal -offset indent
	35	ahci_load="YES"
	36	.Ed
	37	.Sh DESCRIPTION
	38	The
	39	.Nm
	40	driver provides support for Serial ATA controllers conforming to the
	41	Advanced Host Controller Interface specification.
	42	.Pp
	43	Several AHCI capable controllers also provide a compatibility mode that
	44	causes them to appear as a traditional ATA controller supported by
	45	.Xr nata 4 .
	46	.Pp
	47	Although
	48	.Nm
	49	controllers are actual ATA controllers, the driver emulates SCSI via a
	50	translation layer.
	51	.Sh LOADER TUNABLES
	52	The following hints may be set in
	53	.Xr loader.conf 5
	54	to control the
	55	.Nm
	56	driver's behavior.
	57	Note that the hint need only exist, so removing it requires commenting it out.
	58	.Pp
	59	Usually both the
	60	.Xr nata 4
	61	and the
	62	.Nm
	63	drivers are loaded.
	64	The
	65	.Xr nata 4
	66	driver will pick up any ata-like devices which the
	67	.Nm
	68	driver misses.
	69	If the
	70	.Nm
	71	driver is disabled the
	72	.Xr nata 4
	73	driver will typically pick up the
	74	.Nm
	75	devices, albeit under the
	76	.Pa ad
	77	disk name rather than the
	78	.Pa da
	79	disk name.
	80	.Bd -literal -offset indent
	81	hint.ahci.disabled=1
	82	.Ed
	83	.Pp
	84	The
	85	.Nm
	86	driver can be told to force a lower-speed 1.5Gb link speed
	87	if necessary, and can also be told to refrain from attempting to send
	88	certain higher-level ATA commands to initialize ATA features which
	89	some devices might not properly implement.
	90	.Bd -literal -offset indent
	91	hint.ahci.force150=1
	92	hint.ahci.nofeatures=1
	93	.Ed
	94	.Sh SYSCTL VARIABLES
	95	Link power management can be set with the sysctl
	96	.Va hw.ahci%d.%d.link_pwr_mgmt
	97	to 0 for `disabled', 1 for `medium', and 2 for `aggressive'.
	98	Link power state can be read with the sysctl
	99	.Va hw.ahci%d.%d.link_pwr_state .
	100	.Sh SEE ALSO
	101	.Xr intro 4 ,
	102	.Xr nata 4 ,
	103	.Xr pci 4 ,
	104	.Xr scsi 4 ,
	105	.Xr sili 4 ,
	106	.Xr loader.conf 5
	107	.Sh HISTORY
	108	The
	109	.Nm
	110	driver first appeared in
	111	.Dx 2.3 .
	112	.Sh AUTHORS
	113	.An -nosplit
	114	The
	115	.Nm
	116	driver was originally written by
	117	.An David Gwynne Aq dlg@openbsd.org
	118	and
	119	.An Christopher Pascoe Aq pascoe@openbsd.org
	120	for
	121	.Ox .
	122	.Pp
	123	It was ported to
	124	.Dx
	125	by
	126	.An Matt Dillon Aq dillon@apollo.backplane.com
	127	who added new features such as hot-plug and port multiplier support.