124 lines
3.6 KiB
Groff
124 lines
3.6 KiB
Groff
.\" $NetBSD: acpiec.4,v 1.6 2010/02/27 20:39:42 snj Exp $
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.\"
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.\" Copyright (c) 2002, 2004, 2010 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd February 27, 2010
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.Dt ACPIEC 4
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.Os
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.Sh NAME
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.Nm acpiec
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.Nd ACPI Embedded Controller
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.Sh SYNOPSIS
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.Cd "acpiec* at acpi?"
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.Cd "acpiecdt* at acpi?"
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.Sh DESCRIPTION
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The
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.Nm
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driver supports ACPI Embedded Controllers.
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.Pp
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An ACPI Embedded Controller
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.Pq Tn EC
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is typically a small microprocessor that is responsible for various tasks
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related to
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.Tn ACPI .
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The primary task is to handle
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.Tn ACPI
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specific interrupts, which are mapped to so-called
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.Tn ACPI
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General Purpose Events
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.Pq Tn GPEs .
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Other possible functions include embedded access to other buses such as the
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.Xr iic 4 .
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.Pp
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The
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.Tn ACPI
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specific events range from user initiated events to events triggered by
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the hardware.
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When such an event occurs, typically either a System Management Interrupt
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.Pq Tn SMI
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or a System Control Interrupt
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.Pq Tn SCI
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is raised.
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The latter is an active, visible, shareable, level interrupt.
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On most Intel chipsets
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.Tn SCI
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is hardwired to the interrupt number 9.
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The main task of an
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.Tn EC
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is to raise a system control interrupt.
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.Pp
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All GPEs generate SCIs.
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A typical example of the internal wiring of
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.Tn GPEs
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could involve
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.Xr gpio 4 :
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when, e.g., the
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.Tn AC
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adapter is connected, a certain
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.Tn GPIO
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line becomes active, a given
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.Tn GPE
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is flagged, and a
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.Tn SCI
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interrupt is raised by the
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.Tn EC ,
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leading to execution of
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.Tn ACPI
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machine code in order to locate the handler associated with the event.
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A corresponding driver,
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.Xr acpiacad 4
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in this case, will finally finish the processing of the event.
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.Pp
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Due to the reasons described above, majority of
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.Tn ACPI
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specific drivers are dysfunctional without
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.Nm .
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It is therefore recommended that
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.Nm
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is always enabled,
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even though it may not be required on some older systems.
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.Sh SEE ALSO
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.Xr acpi 4
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.Sh HISTORY
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The
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.Nm
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driver
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appeared in
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.Nx 1.6 .
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.Sh CAVEATS
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Many machines depend on early attachment of
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.Nm .
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In such cases the information required by
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.Nm
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should be available as a separate and optional
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Embedded Controller Descriptor Table
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.Pq Tn ECDT .
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If an
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.Tn ECDT
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is not available or early attachment can not be carried out due other reasons,
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the initialization of the whole
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.Xr acpi 4
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subsystem may be problematic.
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