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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
+        "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
+
+<book id="regulator-api">
+ <bookinfo>
+  <title>Voltage and current regulator API</title>
+
+  <authorgroup>
+   <author>
+    <firstname>Liam</firstname>
+    <surname>Girdwood</surname>
+    <affiliation>
+     <address>
+      <email>lrg@slimlogic.co.uk</email>
+     </address>
+    </affiliation>
+   </author>
+   <author>
+    <firstname>Mark</firstname>
+    <surname>Brown</surname>
+    <affiliation>
+     <orgname>Wolfson Microelectronics</orgname>
+     <address>
+      <email>broonie@opensource.wolfsonmicro.com</email>
+     </address>
+    </affiliation>
+   </author>
+  </authorgroup>
+
+  <copyright>
+   <year>2007-2008</year>
+   <holder>Wolfson Microelectronics</holder>
+  </copyright>
+  <copyright>
+   <year>2008</year>
+   <holder>Liam Girdwood</holder>
+  </copyright>
+
+  <legalnotice>
+   <para>
+     This documentation is free software; you can redistribute
+     it and/or modify it under the terms of the GNU General Public
+     License version 2 as published by the Free Software Foundation.
+   </para>
+
+   <para>
+     This program is distributed in the hope that it will be
+     useful, but WITHOUT ANY WARRANTY; without even the implied
+     warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+     See the GNU General Public License for more details.
+   </para>
+
+   <para>
+     You should have received a copy of the GNU General Public
+     License along with this program; if not, write to the Free
+     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+     MA 02111-1307 USA
+   </para>
+
+   <para>
+     For more details see the file COPYING in the source
+     distribution of Linux.
+   </para>
+  </legalnotice>
+ </bookinfo>
+
+<toc></toc>
+
+  <chapter id="intro">
+    <title>Introduction</title>
+    <para>
+        This framework is designed to provide a standard kernel
+        interface to control voltage and current regulators.
+    </para>
+    <para>
+        The intention is to allow systems to dynamically control
+        regulator power output in order to save power and prolong
+        battery life.  This applies to both voltage regulators (where
+        voltage output is controllable) and current sinks (where current
+        limit is controllable).
+    </para>
+    <para>
+        Note that additional (and currently more complete) documentation
+        is available in the Linux kernel source under
+        <filename>Documentation/power/regulator</filename>.
+    </para>
+
+    <sect1 id="glossary">
+       <title>Glossary</title>
+       <para>
+        The regulator API uses a number of terms which may not be
+        familiar:
+       </para>
+       <glossary>
+
+         <glossentry>
+           <glossterm>Regulator</glossterm>
+           <glossdef>
+             <para>
+        Electronic device that supplies power to other devices.  Most
+        regulators can enable and disable their output and some can also
+        control their output voltage or current.
+             </para>
+           </glossdef>
+         </glossentry>
+
+         <glossentry>
+           <glossterm>Consumer</glossterm>
+           <glossdef>
+             <para>
+        Electronic device which consumes power provided by a regulator.
+        These may either be static, requiring only a fixed supply, or
+        dynamic, requiring active management of the regulator at
+        runtime.
+             </para>
+           </glossdef>
+         </glossentry>
+
+         <glossentry>
+           <glossterm>Power Domain</glossterm>
+           <glossdef>
+             <para>
+        The electronic circuit supplied by a given regulator, including
+        the regulator and all consumer devices.  The configuration of
+        the regulator is shared between all the components in the
+        circuit.
+             </para>
+           </glossdef>
+         </glossentry>
+
+         <glossentry>
+           <glossterm>Power Management Integrated Circuit</glossterm>
+           <acronym>PMIC</acronym>
+           <glossdef>
+             <para>
+        An IC which contains numerous regulators and often also other
+        subsystems.  In an embedded system the primary PMIC is often
+        equivalent to a combination of the PSU and southbridge in a
+        desktop system.
+             </para>
+           </glossdef>
+         </glossentry>
+        </glossary>
+     </sect1>
+  </chapter>
+
+  <chapter id="consumer">
+     <title>Consumer driver interface</title>
+     <para>
+       This offers a similar API to the kernel clock framework.
+       Consumer drivers use <link
+       linkend='API-regulator-get'>get</link> and <link
+       linkend='API-regulator-put'>put</link> operations to acquire and
+       release regulators.  Functions are
+       provided to <link linkend='API-regulator-enable'>enable</link>
+       and <link linkend='API-regulator-disable'>disable</link> the
+       reguator and to get and set the runtime parameters of the
+       regulator.
+     </para>
+     <para>
+       When requesting regulators consumers use symbolic names for their
+       supplies, such as "Vcc", which are mapped into actual regulator
+       devices by the machine interface.
+     </para>
+     <para>
+        A stub version of this API is provided when the regulator
+        framework is not in use in order to minimise the need to use
+        ifdefs.
+     </para>
+
+     <sect1 id="consumer-enable">
+       <title>Enabling and disabling</title>
+       <para>
+         The regulator API provides reference counted enabling and
+         disabling of regulators. Consumer devices use the <function><link
+         linkend='API-regulator-enable'>regulator_enable</link></function>
+         and <function><link
+         linkend='API-regulator-disable'>regulator_disable</link>
+         </function> functions to enable and disable regulators.  Calls
+         to the two functions must be balanced.
+       </para>
+       <para>
+         Note that since multiple consumers may be using a regulator and
+         machine constraints may not allow the regulator to be disabled
+         there is no guarantee that calling
+         <function>regulator_disable</function> will actually cause the
+         supply provided by the regulator to be disabled. Consumer
+         drivers should assume that the regulator may be enabled at all
+         times.
+       </para>
+     </sect1>
+
+     <sect1 id="consumer-config">
+       <title>Configuration</title>
+       <para>
+         Some consumer devices may need to be able to dynamically
+         configure their supplies.  For example, MMC drivers may need to
+         select the correct operating voltage for their cards.  This may
+         be done while the regulator is enabled or disabled.
+       </para>
+       <para>
+         The <function><link
+         linkend='API-regulator-set-voltage'>regulator_set_voltage</link>
+         </function> and <function><link
+         linkend='API-regulator-set-current-limit'
+         >regulator_set_current_limit</link>
+         </function> functions provide the primary interface for this.
+         Both take ranges of voltages and currents, supporting drivers
+         that do not require a specific value (eg, CPU frequency scaling
+         normally permits the CPU to use a wider range of supply
+         voltages at lower frequencies but does not require that the
+         supply voltage be lowered).  Where an exact value is required
+         both minimum and maximum values should be identical.
+       </para>
+     </sect1>
+
+     <sect1 id="consumer-callback">
+       <title>Callbacks</title>
+       <para>
+          Callbacks may also be <link
+          linkend='API-regulator-register-notifier'>registered</link>
+          for events such as regulation failures.
+       </para>
+     </sect1>
+   </chapter>
+
+   <chapter id="driver">
+     <title>Regulator driver interface</title>
+     <para>
+       Drivers for regulator chips <link
+       linkend='API-regulator-register'>register</link> the regulators
+       with the regulator core, providing operations structures to the
+       core.  A <link
+       linkend='API-regulator-notifier-call-chain'>notifier</link> interface
+       allows error conditions to be reported to the core.
+     </para>
+     <para>
+       Registration should be triggered by explicit setup done by the
+       platform, supplying a <link
+       linkend='API-struct-regulator-init-data'>struct
+       regulator_init_data</link> for the regulator containing
+       <link linkend='machine-constraint'>constraint</link> and
+       <link linkend='machine-supply'>supply</link> information.
+     </para>
+   </chapter>
+
+   <chapter id="machine">
+     <title>Machine interface</title>
+     <para>
+       This interface provides a way to define how regulators are
+       connected to consumers on a given system and what the valid
+       operating parameters are for the system.
+     </para>
+
+     <sect1 id="machine-supply">
+       <title>Supplies</title>
+       <para>
+         Regulator supplies are specified using <link
+         linkend='API-struct-regulator-consumer-supply'>struct
+         regulator_consumer_supply</link>.  This is done at
+         <link linkend='driver'>driver registration
+         time</link> as part of the machine constraints.
+       </para>
+     </sect1>
+
+     <sect1 id="machine-constraint">
+       <title>Constraints</title>
+       <para>
+         As well as definining the connections the machine interface
+         also provides constraints definining the operations that
+         clients are allowed to perform and the parameters that may be
+         set.  This is required since generally regulator devices will
+         offer more flexibility than it is safe to use on a given
+         system, for example supporting higher supply voltages than the
+         consumers are rated for.
+       </para>
+       <para>
+         This is done at <link linkend='driver'>driver
+         registration time</link> by providing a <link
+         linkend='API-struct-regulation-constraints'>struct
+         regulation_constraints</link>.
+       </para>
+       <para>
+         The constraints may also specify an initial configuration for the
+         regulator in the constraints, which is particularly useful for
+         use with static consumers.
+       </para>
+     </sect1>
+  </chapter>
+
+  <chapter id="api">
+    <title>API reference</title>
+    <para>
+      Due to limitations of the kernel documentation framework and the
+      existing layout of the source code the entire regulator API is
+      documented here.
+    </para>
+!Iinclude/linux/regulator/consumer.h
+!Iinclude/linux/regulator/machine.h
+!Iinclude/linux/regulator/driver.h
+!Edrivers/regulator/core.c
+  </chapter>
+</book>