123 lines
3.9 KiB
Groff
123 lines
3.9 KiB
Groff
.\" $NetBSD: nvram.4,v 1.3 2008/04/30 13:10:56 martin Exp $
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.\"
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.\" Copyright (c) 2007 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Tim Rightnour
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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 March 1, 2007
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.Dt NVRAM 4 prep
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.Os
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.Sh NAME
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.Nm nvram
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.Nd PReP nvram interface
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.Sh SYNOPSIS
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.In machine/nvram.h
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.Sh DESCRIPTION
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The file
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.Nm /dev/nvram
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is an interface to the PReP NVRAM, including the Global Environment Area.
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This interface is highly stylized;
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ioctls are used for all operations.
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These ioctls refer to individual variables in the
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Global Environment Area and thier values.
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.Pp
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The calls that take and/or return a variable
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use a pointer to an
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.Li int
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variable for this purpose;
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others use a pointer to an
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.Li struct pnviocdesc
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descriptor,
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which contains a variable and two counted strings.
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The first string comprises the fields
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.Li pnv_namelen
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(an
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.Li int )
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and
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.Li pnv_name
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(a
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.Li "char *" ) ,
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giving the name of a field.
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The second string comprises the fields
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.Li pnv_buflen
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and
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.Li pnv_buf ,
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used analogously.
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These two counted strings work in a
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.Dq value-result
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fashion.
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At entry to the ioctl,
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the counts are expected to reflect the buffer size;
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on return,
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the counts are updated to reflect the buffer contents.
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.Pp
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The following ioctls are supported:
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.Bl -tag -width PNVIOCGETNEXTNAME
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.It PNVIOCGETNEXTNAME
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Takes a variable name and returns the name of the following variable.
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If a
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.Dv NULL
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is passed as the variable name, the first variable name
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will be returned.
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If the last variable is given as an argument, the ioctl will return
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.Er EINVAL .
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.It Dv PNVIOCGET
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Fills in the value of the named property for the given variable.
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If no such property is associated with that variable,
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the value length is set to \-1.
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If the named property exists but has no value,
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the value length is set to 0.
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.It Dv PNVIOCSET
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Writes the given value under the given name.
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.It Dv PNVIOCGETNUMGE
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Returns the number of variables in the Global Environment Area.
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.El
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.Sh FILES
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.Pa /dev/nvram
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.Sh ERRORS
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The following may result in rejection of an operation:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The given variable name does not exist.
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.It Bq Er EINVAL
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The buffer set up to retrieve values from the nvram was not large enough
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to hold the result.
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.El
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.Sh SEE ALSO
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.Xr ioctl 2
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.Pp
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.Pa PowerPC Reference Platform Specification Version 1.1, Section 5.5
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.Sh BUGS
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Due to limitations within the
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.Nm
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itself, these functions run at elevated priority
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and may adversely affect system performance.
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.Pp
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.Dv PNVIOCSET
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is not currently supported, making the
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.Nm
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driver read-only at this time.
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