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35 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Copyright (c) 2016, 2020 OpenPOWER Foundation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xl="http://www.w3.org/1999/xlink"
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xml:id="dbdoclet.50569333_15433"
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version="5.0" xml:lang="en">
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<title>Non-Volatile Memory</title>
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<para>This chapter describes the requirements relating to Non-Volatile
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Memory. Non-Volatile Memory is the repository for system information that must
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be persistent across reboots and power cycles. </para>
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<section xml:id="sec_nvram_sys_req">
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<title>System Requirements</title>
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<variablelist>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_sys_req"
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xrefstyle="select: labelnumber nopage"/>-1.</emphasis></term>
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<listitem>
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<para>Platforms must implement at least 8 KB of
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Non-Volatile Memory. The actual amount is platform dependent and must allow for
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4 KB for the OS. Platforms must provide an additional 4 KB for each installed
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OS beyond the first.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_sys_req"
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xrefstyle="select: labelnumber nopage"/>-2.</emphasis></term>
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<listitem>
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<para>Non-Volatile Memory must maintain its
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contents in the absence of system power.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_sys_req"
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xrefstyle="select: labelnumber nopage"/>-3.</emphasis></term>
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<listitem>
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<para>Firmware must reinitialize NVRAM to a
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bootable state if NVRAM data corruption is detected.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_sys_req"
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xrefstyle="select: labelnumber nopage"/>-4.</emphasis></term>
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<listitem>
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<para>OSs must reinitialize their own NVRAM
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partitions if NVRAM data corruption is detected. OSs may create free space from
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the first corrupted NVRAM partition header to the end of NVRAM and utilize this
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area to initialize their NVRAM partitions.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para><emphasis role="bold">Hardware Implementation Note:</emphasis> The NVRAM terminology used in this
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chapter goes back to historic implementations that have used battery-powered
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RAM to implement the non-volatile memory. It should be understood that this is
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not the only possible implementation. Implementers need to understand that
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there are no limits on the frequency of writing to the non-volatile memory, so
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certain technologies may not be applicable. Also, it should be noted that the
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<emphasis>nvram-fetch</emphasis> and <emphasis>nvram-store</emphasis> RTAS
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calls do not allow a “busy” Status return, and this may further
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limit the implementation choices.</para>
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<para><emphasis role="bold">Software Implementation Note:</emphasis> Refer to <xref linkend="dbdoclet.50569332_26944"/>
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for information on accessing NVRAM.</para>
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</section>
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<section xml:id="sec_nvram_structure">
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<title>Structure</title>
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<para>NVRAM is formatted as a set of NVRAM partitions that adhere to the
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structure in <xref linkend="dbdoclet.50569333_37259"/>. NVRAM partitions are
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prefixed with a header containing <emphasis>signature</emphasis>,
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<emphasis>checksum</emphasis>, <emphasis>length</emphasis>, and
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<emphasis>name</emphasis> fields. The structure of the <emphasis>data</emphasis> field
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is defined by the NVRAM partition creator/owner (designated by
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<emphasis>signature</emphasis> and <emphasis>name</emphasis>). </para>
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<variablelist>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_structure"
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xrefstyle="select: labelnumber nopage"/>-1.</emphasis></term>
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<listitem>
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<para>NVRAM partitions must be structured as shown
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in <xref linkend="dbdoclet.50569333_37259"/>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_structure"
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xrefstyle="select: labelnumber nopage"/>-2.</emphasis></term>
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<listitem>
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<para>All NVRAM space must be accounted for by
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NVRAM partitions.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="sec_nvram_structure"
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xrefstyle="select: labelnumber nopage"/>-3.</emphasis></term>
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<listitem>
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<para>All IBM-defined NVRAM partitions that are
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intended to be IBM-unique must have names prefixed with the ASCII
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representation of the four characters: <emphasis>ibm,</emphasis>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para><emphasis role="bold">Software Implementation Note:</emphasis> Although the data
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areas of NVRAM partitions are not required to have error checking, it is
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strongly recommended that the system software implement robust data structures
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and error checking. Loss of NVRAM structures due to data corruption can be
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catastrophic, potentially leading to OS reinstallation and/or complete system
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initialization.</para>
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</section>
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<section>
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<title>Signatures</title>
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<para>The <emphasis>signature</emphasis> field is used as the first level
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of NVRAM partition identification. <xref linkend="dbdoclet.50569333_24820"/>
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lists all the currently defined signature types and their ownership classes.
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The ownership class determines the permission of a particular system software
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component to create and/or modify NVRAM partitions and/or NVRAM partition
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contents. All NVRAM partitions may be read by any system software component,
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but the ownership class has exclusive write permission. Global ownership gives
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read/write permission to all system software components. These restrictions are
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made to minimize the possibility of corruption of NVRAM during update
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activities.</para>
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<para><emphasis role="bold">Hardware and Software Implementation Note:</emphasis> It is recommended that
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NVRAM partitions be ordered on the signature field with the lowest value
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signature NVRAM partition at the lowest NVRAM address (with the exception of
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signature = 0x7F, free space). This will minimize the effect of NVRAM data
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corruption on system operation.</para>
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<table frame="all" pgwide="1" xml:id="dbdoclet.50569333_37259">
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<title>NVRAM Structure </title>
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<tgroup cols="3">
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<colspec colname="c1" colwidth="15*" align="center"/>
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<colspec colname="c2" colwidth="15*" align="center"/>
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<colspec colname="c3" colwidth="70*"/>
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<thead valign="middle">
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<row>
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<entry>
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<para>
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<emphasis role="bold">Field Name</emphasis>
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</para>
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</entry>
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<entry>
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<para>
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<emphasis role="bold">Size</emphasis>
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</para>
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</entry>
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<entry align="center">
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<para>
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<emphasis role="bold">Description</emphasis>
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</para>
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</entry>
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</row>
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</thead>
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<tbody valign="middle">
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<row>
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<entry>
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<para> signature</para>
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</entry>
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<entry>
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<para> 1 byte</para>
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</entry>
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<entry>
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<para> The <emphasis>signature</emphasis> field is used to
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identify the NVRAM partition type and provide some level of checking for
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overall NVRAM contamination. Signature assignments are given in
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<xref linkend="dbdoclet.50569333_24820"/>.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para>checksum</para>
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</entry>
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<entry>
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<para> 1 byte</para>
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</entry>
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<entry>
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<para> The <emphasis>checksum</emphasis> field is included to
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provide a check on the validity of the header. The checksum covers the
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<emphasis>signature</emphasis>, <emphasis>length</emphasis>, and
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<emphasis>name</emphasis> fields and is calculated (on a byte by byte or equivalent
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basis) by: add, and add 1 back to the sum if a carry resulted as demonstrated
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with the following program listing.<programlisting><![CDATA[unsigned char sumcheck(bp,nbytes)
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unsigned char *bp; /* buffer pointer */
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unsigned int nbytes; /* number of bytes to sum */
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{
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unsigned char b_data; /* byte data */
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unsigned char i_sum; /* intermediate sum */
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unsigned char c_sum; /* current sum */
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for (c_sum = 0; nbytes; nbytes--)
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{
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b_data = *bp++; /* read byte from buffer */
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i_sum = c_sum + b_data; /* add to current sum */
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if(i_sum < c_sum) /* did a carry out result? */
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i_sum += 1; /* if so, add 1 */
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c_sum = i_sum; /* copy to current sum */
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}
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return (c_sum);
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}]]></programlisting></para>
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<para>This checksum algorithm guarantees 0 to be an impossible
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calculated value. A valid header cannot have a checksum of zero.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para> length</para>
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</entry>
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<entry>
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<para> 2 bytes</para>
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</entry>
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<entry>
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<para> The <emphasis>length</emphasis> field designates the
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total length of the NVRAM partition, in 16-byte blocks, beginning with the
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signature and ending with the last byte of the data area. A length of zero is
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invalid.</para>
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<para><emphasis role="bold">Software Implementation Note:</emphasis> The
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<emphasis>length</emphasis> field must always provide valid offsets to the
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next header since an invalid length effectively causes the loss of access to
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every NVRAM partition beyond it.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para> name</para>
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</entry>
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<entry>
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<para> 12 bytes</para>
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</entry>
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<entry>
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<para> The <emphasis>name</emphasis> field is a 12 byte string
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(or a NULL-terminated string of less than 12 bytes) used to identify a
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particular NVRAM partition within a signature group. In order to reduce the
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likelihood of a naming conflict, each platform-specific or OS-specific NVRAM
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partition name should be prefixed with a company name as specified under the
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description of the “name” string in the
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<emphasis><xref linkend="dbdoclet.50569387_45524"/>,</emphasis> that is, a company name string
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in one of the three forms described in the reference, followed by a comma
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(“,”). If the company name string is null, the name will be
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interpreted as “other”.</para>
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<para>Before assigning a new name to a NVRAM partition, software
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should scan the existing NVRAM partitions and ensure that an unwanted name
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conflict is not created.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para> data</para>
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</entry>
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<entry>
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<para><emphasis>length</emphasis> minus 16 bytes</para>
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</entry>
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<entry>
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<para> The structure of the <emphasis>data</emphasis> area is
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controlled by the creator/owner of the NVRAM partition.</para>
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table frame="all" pgwide="1" xml:id="dbdoclet.50569333_24820">
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<title>NVRAM Signatures </title>
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<tgroup cols="5">
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<colspec colname="c1" colwidth="15*" align="center"/>
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<colspec colname="c2" colwidth="15*" align="center"/>
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<colspec colname="c3" colwidth="15*" align="center"/>
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<colspec colname="c4" colwidth="15*" align="center"/>
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<colspec colname="c5" colwidth="40*"/>
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<thead valign="middle">
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<row>
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<entry>
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<para>
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<emphasis role="bold">Signature <?linebreak?>(see note)</emphasis>
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</para>
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</entry>
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<entry>
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<para>
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<emphasis role="bold">Signature Type</emphasis>
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</para>
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</entry>
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<entry>
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<para>
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<emphasis role="bold">Ownership Class</emphasis>
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</para>
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</entry>
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<entry>
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<para>
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<emphasis role="bold"># Required</emphasis>
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</para>
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</entry>
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<entry align="center">
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<para>
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<emphasis role="bold">Description</emphasis>
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</para>
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</entry>
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</row>
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</thead>
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<tbody valign="middle">
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<row>
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<entry>
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<para> 0x70</para>
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</entry>
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<entry>
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<para> System</para>
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</entry>
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<entry>
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<para> Global</para>
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</entry>
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<entry>
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<para> 1</para>
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</entry>
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<entry>
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<para> For configuration variables.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para> 0x7E</para>
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</entry>
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<entry>
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<para> Vendor-defined </para>
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</entry>
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<entry>
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<para> Global</para>
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</entry>
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<entry>
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<para> 0 to n</para>
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</entry>
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<entry>
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<para> “name” prefix required.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para> 0x7F</para>
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</entry>
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<entry>
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<para> Free Space</para>
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</entry>
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<entry>
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<para> Global</para>
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</entry>
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<entry>
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<para> 0 to n</para>
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</entry>
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<entry>
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<para> This signature is used to mark free space in the NVRAM
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array. The <emphasis>name</emphasis> field of all signature 0x7F NVRAM
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partitions must be set to 0x7...77.</para>
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</entry>
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</row>
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<row>
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<entry>
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<para> 0xA0</para>
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</entry>
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<entry>
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<para> OS</para>
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</entry>
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<entry>
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<para> Any OS</para>
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</entry>
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<entry>
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<para> 0 to n</para>
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</entry>
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<entry>
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<para> General OS usage.</para>
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</entry>
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</row>
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<row>
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<entry nameend="c5" namest="c1" align="left">
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<para><emphasis role="bold">Note:</emphasis> Any signature not defined above is reserved, and
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signatures 0x02, 0x50, 0x51, 0x52, 0x71, and 0x72 are reserved for legacy
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reasons.</para>
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</section>
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<section>
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<title>Architected NVRAM Partitions</title>
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|
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<section xml:id="dbdoclet.50569333_25869">
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<title>System (0x70)</title>
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<para>System NVRAM partitions are used for storing information
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(typically, configuration variables) accessible to both OF and the OS. Refer to
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<xref linkend="dbdoclet.50569368_91814"/> for the definition of the contents of the
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System NVRAM partition named <emphasis role="bold"><literal>common</literal></emphasis>.</para>
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<variablelist>
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="dbdoclet.50569333_25869"
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xrefstyle="select: labelnumber nopage"/>-1.</emphasis></term>
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<listitem>
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<para>Every system NVRAM must contain a System
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NVRAM partition with the NVRAM partition name = <emphasis role="bold"><literal>common</literal></emphasis>.</para>
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</listitem>
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</varlistentry>
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|
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="dbdoclet.50569333_25869"
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xrefstyle="select: labelnumber nopage"/>-2.</emphasis></term>
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<listitem>
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<para>Data in the <emphasis role="bold"><literal>common</literal></emphasis>
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NVRAM partition must be stored as NULL-terminated strings of the form:
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<emphasis><name>=<string></emphasis> and the
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<emphasis>data</emphasis> area must be terminated with at least two NULL
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characters.</para>
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</listitem>
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</varlistentry>
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|
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<varlistentry>
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<term><emphasis role="bold">R1-<xref linkend="dbdoclet.50569333_25869"
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xrefstyle="select: labelnumber nopage"/>-3.</emphasis></term>
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<listitem>
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<para>All <emphasis>names</emphasis> used in
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the <emphasis role="bold"><literal>common</literal></emphasis> NVRAM partition must be unique.</para>
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</listitem>
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</varlistentry>
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|
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<varlistentry>
|
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<term><emphasis role="bold">R1-<xref linkend="dbdoclet.50569333_25869"
|
|
xrefstyle="select: labelnumber nopage"/>-4.</emphasis></term>
|
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<listitem>
|
|
<para>Device and file specifications used in
|
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the <emphasis role="bold"><literal>common</literal></emphasis> NVRAM partition must follow IEEE Std 1275
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nomenclature conventions.</para>
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</listitem>
|
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</varlistentry>
|
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</variablelist>
|
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|
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<section>
|
|
<title>System NVRAM Partition</title>
|
|
<para>The System NVRAM partition, with name = <emphasis role="bold"><literal>common</literal></emphasis>,
|
|
contains information that is accessible to both OF and OSs.
|
|
The contents of this NVRAM partition are represented in the OF device tree as
|
|
properties (i.e., (<emphasis>name</emphasis>, <emphasis>value</emphasis>)
|
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pairs) in the <emphasis role="bold"><literal>/options</literal></emphasis> node. While OF is available, the
|
|
OS can alter the contents of these properties by using the
|
|
<emphasis>setprop</emphasis> client interface service. When OF is no longer available,
|
|
the OS can alter the contents of the System NVRAM partition itself, following
|
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the rules below for the formats of the <emphasis>name</emphasis> and
|
|
<emphasis>value</emphasis>. Information is stored in the System NVRAM
|
|
partition as a sequence of (<emphasis>name</emphasis>,
|
|
<emphasis>value</emphasis>) pairs in the following format: </para>
|
|
<para><emphasis>name = value</emphasis></para>
|
|
<para>where <emphasis>name</emphasis> follows the rules defined in
|
|
<xref linkend="dbdoclet.50569333_24970"/> and <emphasis>value</emphasis> follows the
|
|
rules defined in <xref linkend="dbdoclet.50569333_36194"/>. The end of the
|
|
sequence of pairs is denoted by a NULL (0x00) byte. </para>
|
|
|
|
<section xml:id="dbdoclet.50569333_24970">
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<title>Name</title>
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<para>Since the data in the System NVRAM partition is an external
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representation of properties of the <emphasis role="bold"><literal>/option</literal></emphasis> node, the
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name component must follow the rules for <emphasis role="bold"><literal>property names</literal></emphasis>
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as defined by Section 3.2.2.1.1 Property names of
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<xref linkend="dbdoclet.50569387_45524"/>; i.e., a string of 1-31 printable
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characters containing no uppercase characters or the characters
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“/”, “\”, “:”, “[“,
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“]” or “@”. In addition to these rules, a naming
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convention is required for OS specific names to avoid name conflicts. Each such
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name must begin with the OS vendor’s OUI followed by a
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“,”; e.g., aapl,<emphasis>xxx</emphasis> or
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ibm,<emphasis>xxx</emphasis>. This introduces separate name spaces for each vendor in which
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it manages its own naming conventions. </para>
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</section>
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<section xml:id="dbdoclet.50569333_36194">
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<title>Value </title>
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<para>The value component of System NVRAM partition data can contain an
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arbitrary number of bytes in the range 0x01 to 0xFF, terminated by a NULL
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(0x00) byte. Bytes in the range 0x01 to 0xFE represent themselves. In order to
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allow arbitrary byte data to be represented, an encoding is used to represent
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strings of 0x00 or 0xFF bytes. This encoding uses the 0xFF byte as an escape,
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indicating that the following byte is encoded as:</para>
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<para>bnnnnnnn</para>
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<para>where b, the most-significant bit, is 0 to represent a sequence of
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0x00 bytes or 1 to represent a sequence of 0xFF bytes. nnnnnnn, the
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least-significant 7 bits, is a binary number (in the range 0x01 to 0x7F) that
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represents the number of repetitions of 0x00 or 0xFF. </para>
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</section>
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<section>
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<title>OF Configuration Variables</title>
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<para>OF configuration variables control the operation of OF. In addition
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to the standard configuration variables defined in
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<xref linkend="dbdoclet.50569387_45524"/>, other configuration variables are defined
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in <xref linkend="dbdoclet.50569374_59715"/>. While such variables are stored in the System
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NVRAM partition as described above, they have additional rules placed on the
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format of the value component. Each configuration variable is also represented
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by a user interface word (of the same name) that returns stack value(s) when
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that word is evaluated. Each also has a platform defined default value; the
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absence of a configuration variable in the System NVRAM partition indicates
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that the value is set to its default value. The format of the external
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representation of configuration variables, and their stack representation, is
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defined by Section 7.4.4.1 Configuration Variables of
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<xref linkend="dbdoclet.50569387_45524"/>; the format depends upon the data type of
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the configuration variable. Whereas the internal storage format is not defined
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by <xref linkend="dbdoclet.50569387_45524"/>, this architecture specifies them
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as described below. The names of configuration variables are defined in <xref
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linkend="dbdoclet.50569387_45524"/>, except as noted otherwise.</para>
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<section>
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<title>Boolean Configuration Variables </title>
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<para>The value of a boolean configuration variable is represented in the
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System NVRAM partition as the string “true” or
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“false”. The following configuration variables are of type
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boolean: </para>
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<itemizedlist mark="none">
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<listitem>
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<para><emphasis role="bold"><literal>auto-boot?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>diag-switch?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>fcode-debug?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>oem-banner?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>oem-logo?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>use-nvramrc?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>little-endian?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>real-mode?</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>menu?</literal></emphasis> (see <xref linkend="dbdoclet.50569327_26247"/>). </para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>Integer Configuration Variables </title>
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<para>The value of an integer configuration variable is represented in
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the System NVRAM partition as a decimal number or a hexadecimal number preceded
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by “0x”. The following configuration variables are of type
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integer:</para>
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<itemizedlist mark="none">
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<listitem>
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<para><emphasis role="bold"><literal>screen-#columns</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>screen-#rows</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>security-#badlogins</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>security-mode</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>selftest-#megs</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>real-base</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>real-size</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>virt-base</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>virt-size</literal></emphasis></para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>load-base</literal></emphasis></para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>String Configuration Variables</title>
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<para>The value of a string configuration variable is represented in the
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System NVRAM partition as the characters of the string. Where multiple
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“lines” of text are represented, each line is terminated by a
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carriage-return (0x0D), a line-feed (0x0A), or carriage-return, line-feed
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sequence (0x0D, 0x0A). The following configuration variables are of type
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string: </para>
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<itemizedlist mark="none">
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<listitem>
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<para><emphasis role="bold"><literal>boot-command</literal></emphasis> [1]</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>boot-device</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>boot-file</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>diag-device</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>diag-file</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>input-device</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>nvramrc</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>oem-banner</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>output-device</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>security-password</literal></emphasis> [1] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>bootinfo-nnnnn</literal></emphasis> [*] </para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>reboot-command</literal></emphasis> [*]</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>ibm,shadow-boot-device</literal></emphasis> [1]</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold"><literal>ibm,last-booted</literal></emphasis> [1]</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>Byte Configuration Variables </title>
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<para>The value of a bytes configuration variable is represented by an
|
|
arbitrary number of bytes, using the encoding escape for values of 0x00 and
|
|
0xFF. The following configuration variables are of type bytes:</para>
|
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<itemizedlist mark="none">
|
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<listitem>
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<para><emphasis role="bold"><literal>oem-logo</literal></emphasis> [1] </para>
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</listitem>
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</itemizedlist>
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</section>
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</section>
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</section>
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|
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<section xml:id="sec_disk_startup">
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<title>DASD Spin-up Control</title>
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<para> In order to reduce the boot time of platforms, a configuration
|
|
variable is defined to communicate from the platform to the OS to what extent
|
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spin-up of hard disk drives can be overlapped. Disk drives generally draw more
|
|
current as the motors spin up to operating speed, thus the capacity of the
|
|
power supply limits the ability to spin up drives simultaneously.</para>
|
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<para>The configuration variable
|
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<emphasis role="bold"><literal>ibm,dasd-spin-interval</literal></emphasis> indicates the minimum time, in seconds, that
|
|
must be allowed between initiating the spin-up of hard disk drives on the
|
|
platform. Presence of this variable potentially allows starting up a drive
|
|
prior to receiving completion status from a drive previously started. The
|
|
absence of this variable implies no platform knowledge regarding the capability
|
|
to overlap and, hence, the OS should wait for the appropriate device status
|
|
before proceeding to subsequent drives (no overlap).</para>
|
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|
|
<variablelist>
|
|
<varlistentry>
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|
<term><emphasis role="bold">R1-<xref linkend="sec_disk_startup"
|
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xrefstyle="select: labelnumber nopage"/>-1.</emphasis></term>
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<listitem>
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<para>If a platform wants to overlap spinning
|
|
up it's hard disk drives to improve boot performance, it must create the
|
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<emphasis role="bold"><literal>ibm,dasd-spin-interval</literal></emphasis> OF configuration variable in the
|
|
NVRAM signature 0x70 NVRAM partition named <emphasis role="bold"><literal>common</literal></emphasis> and set
|
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it equal to an integer that represents the minimum time, in seconds, that must
|
|
be allowed between initiating the spin-up of drives on the platform.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para><emphasis role="bold">Firmware Implementation Note:</emphasis> The platform
|
|
should provide a user-friendly interface to this variable to allow for the
|
|
possibility of a user installing hard disks that do not conform to the original
|
|
setting of the variable.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section xml:id="sec_free_space">
|
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<title>Free Space (0x7F)</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><emphasis role="bold">R1-<xref linkend="sec_free_space"
|
|
xrefstyle="select: labelnumber nopage"/>-1.</emphasis></term>
|
|
<listitem>
|
|
<para>All unused NVRAM space must be included
|
|
in a signature = 0x7F Free Space NVRAM partition.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">R1-<xref linkend="sec_free_space"
|
|
xrefstyle="select: labelnumber nopage"/>-2.</emphasis></term>
|
|
<listitem>
|
|
<para>All Free Space NVRAM partitions must have
|
|
the <emphasis>name</emphasis> field set to 0x7...77.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</section>
|
|
</section>
|
|
|
|
<section xml:id="dbdoclet.50569333_13442">
|
|
<title>NVRAM Space Management</title>
|
|
<para>The only NVRAM partitions whose size an OS can modify are OS and Free
|
|
Space signature NVRAM partitions. As NVRAM partitions are created and modified
|
|
by an OS, it is likely that free space will become fragmented; free space
|
|
consolidation may become necessary.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><emphasis role="bold">R1-<xref linkend="dbdoclet.50569333_13442"
|
|
xrefstyle="select: labelnumber nopage"/>-1.</emphasis></term>
|
|
<listitem>
|
|
<para>An OS must not move or delete any NVRAM
|
|
partition, except OS and Free Space signature NVRAM partitions. </para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">R1-<xref linkend="dbdoclet.50569333_13442"
|
|
xrefstyle="select: labelnumber nopage"/>-2.</emphasis></term>
|
|
<listitem>
|
|
<para>The NVRAM partition header checksum must be
|
|
calculated as shown in <xref linkend="dbdoclet.50569333_37259"/>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</section>
|
|
</chapter>
|