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+<div class="document" id="power-management-of-non-virtualised-devices">
<h1 class="title">Power Management of Non-Virtualised Devices</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<tr class="field"><th class="docinfo-name">Type:</th><td class="field-body">Documentary</td>
</tr>
<tr><th class="docinfo-name">Status:</th>
-<td>Draft</td></tr>
+<td>Final</td></tr>
<tr class="field"><th class="docinfo-name">TinyOS-Version:</th><td class="field-body">2.x</td>
</tr>
<tr><th class="docinfo-name">Author:</th>
<td>Kevin Klues, Vlado Handziski, Jan-Hinrich Hauer, Phil Levis</td></tr>
-<tr class="field"><th class="docinfo-name">Draft-Created:</th><td class="field-body">11-Jan-2006</td>
-</tr>
-<tr class="field"><th class="docinfo-name">Draft-Version:</th><td class="field-body">1.7</td>
-</tr>
-<tr class="field"><th class="docinfo-name">Draft-Modified:</th><td class="field-body">2007-02-21</td>
-</tr>
-<tr class="field"><th class="docinfo-name">Draft-Discuss:</th><td class="field-body">TinyOS Developer List
-<tinyos-devel at mail.millennium.berkeley.edu></td>
-</tr>
</tbody>
</table>
-<div class="document" id="power-management-of-non-virtualised-devices">
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">This memo documents a part of TinyOS for the TinyOS Community, and
of this memo is unlimited. This memo is in full compliance with TEP
1.</p>
</div>
-<div class="section" id="abstract">
-<h1><a name="abstract">Abstract</a></h1>
+<div class="section">
+<h1><a id="abstract" name="abstract">Abstract</a></h1>
<p>This memo documents how TinyOS 2.x manages the power state of physical
(not virtualised) abstractions.</p>
</div>
-<div class="section" id="introduction">
-<h1><a name="introduction">1. Introduction</a></h1>
+<div class="section">
+<h1><a id="introduction" name="introduction">1. Introduction</a></h1>
<p>TinyOS platforms have limited energy. A unified power management
-strategy for all devices and peripherpals is not feasible, as
+strategy for all devices and peripherals is not feasible, as
they vary significantly in warm-up times, power profiles, and
operation latencies. While some devices, such as
microcontrollers, can efficiently calculate their lowest possible
power state very quickly, others, such as sensors with warm-up
times, require external knowledge to do so.</p>
-<p>In TinyOS 1.x, an application is responsible for all power management.
+<p>In TinyOS 1.x, applications are responsible for all power management.
Low-level subsystems, such as an SPI bus, are explicitly powered on
and off by higher level abstractions. This approach of deep calls
-to StdControl.start and StdControl.stop introduces strange behaviors
+to <tt class="docutils literal"><span class="pre">StdControl.start()</span></tt> and <tt class="docutils literal"><span class="pre">StdControl.stop()</span></tt> introduces strange behaviors
and can get in the way of power conservation. Turning off the radio
on the Telos platform, for example, turns off the SPI bus and therefore
prevents the flash driver from working. Additionally, the microcontroller
devices are not virtualised in the sense that access to
them must be explicitly requested and released by their users.</p>
</div>
-<div class="section" id="power-management-models">
-<h1><a name="power-management-models">2. Power Management Models</a></h1>
+<div class="section">
+<h1><a id="power-management-models" name="power-management-models">2. Power Management Models</a></h1>
<p>There are two different models to managing the power state of a
peripheral in TinyOS: <em>explicit power management</em> and <em>implicit
power management</em>.</p>
<p>The explicit model provides a means for a single client to manually
control the power state of a dedicated physical device (as defined by
<a class="citation-reference" href="#tep108" id="id3" name="id3">[TEP108]</a>). Whenever this client tells the device to power up or down
-it does so without delay (albeit that caused by hardware). This model
+it does so without delay (except for delays in the hardware of course).
+This model
can be particularly useful when the control information driving the
selection of the proper power state of a device relies on external
logic contained in higher level components. The following section
clients. For example, when a client requests the ADC, this implies
the ADC should be on; if there are no requests of the ADC, this implies
it should be off. Therefore shared devices do not need to provide a
-power control interface. They can use an implicit power management policy.
+power control interface. They can use an implicit power management policy.
Section 4.2 discusses this in more detail.:</p>
<pre class="literal-block">
/|\ /|\
| |
Data Interface Resource
- | |
+ | |
-----------------------------------------------------------------------
| Shared Device (implicitly power managed) |
-----------------------------------------------------------------------
--------------------------------- --------------------------------
</pre>
</div>
-<div class="section" id="explicit-power-management">
-<h1><a name="explicit-power-management">3. Explicit Power Management</a></h1>
+<div class="section">
+<h1><a id="explicit-power-management" name="explicit-power-management">3. Explicit Power Management</a></h1>
<p>Just as in TinyOS 1.x, TinyOS 2.x has <tt class="docutils literal"><span class="pre">StdControl</span></tt> and <tt class="docutils literal"><span class="pre">SplitControl</span></tt>
interfaces in order to control the on and off
power states of explicitly managed peripherals. TinyOS 2.x also
provide one of these three interfaces.
The selection of the right interface depends on the
latencies involved in changing between these two states as well as the
-nature of the code (sync or async) executing any of the interfaces
+nature of the code (sync or async) executing any of the interface's
commands.</p>
-<div class="section" id="power-management-with-stdcontrol">
-<h2><a name="power-management-with-stdcontrol">3.1 Power Management with <tt class="docutils literal"><span class="pre">StdControl</span></tt></a></h2>
+<div class="section">
+<h2><a id="power-management-with-stdcontrol" name="power-management-with-stdcontrol">3.1 Power Management with <tt class="docutils literal"><span class="pre">StdControl</span></tt></a></h2>
<p>Whenever the powerup and powerdown times of a non-virtualised device
-are negligible, they SHOULD provide the <tt class="docutils literal"><span class="pre">StdControl</span></tt> interface as
+are negligible, they SHOULD provide the <tt class="docutils literal"><span class="pre">StdControl</span></tt> interface as
defined below:</p>
<pre class="literal-block">
interface StdControl {
device MUST be completely powered on, allowing calls to commands of other
interfaces implemented by the device to succeed.</p>
<p>Upon the successful return of a call to <tt class="docutils literal"><span class="pre">StdControl.stop()</span></tt>, a
-device MUST be completely powered down, and any calls to commands
-of other interfaces implemented by that device MUST return FAIL or EOFF.</p>
+device MUST be completely powered down, and any calls to commands
+of other interfaces implemented by that device that actually access
+the device hardware MUST return FAIL or EOFF.</p>
<p>If a device is not able to complete the <tt class="docutils literal"><span class="pre">StdControl.start()</span></tt> or
<tt class="docutils literal"><span class="pre">StdControl.stop()</span></tt> request for any reason, it MUST return FAIL.</p>
<p>Based on these specifications, the following matrix has been created
<col width="31%" />
</colgroup>
<thead valign="bottom">
-<tr><th>Call</th>
-<th>Device On</th>
-<th>Device Off</th>
+<tr><th class="head">Call</th>
+<th class="head">Device On</th>
+<th class="head">Device Off</th>
</tr>
</thead>
<tbody valign="top">
}
</pre>
</div>
-<div class="section" id="power-management-with-splitcontrol">
-<h2><a name="power-management-with-splitcontrol">3.2 Power Management with <tt class="docutils literal"><span class="pre">SplitControl</span></tt></a></h2>
+<div class="section">
+<h2><a id="power-management-with-splitcontrol" name="power-management-with-splitcontrol">3.2 Power Management with <tt class="docutils literal"><span class="pre">SplitControl</span></tt></a></h2>
<p>When a device's powerup and powerdown times are non-negligible, the
-<em>``SplitControl``</em> interface MUST be used in place of the <em>``StdControl``</em>
+<em>``SplitControl``</em> interface SHOULD be used in place of the <em>``StdControl``</em>
interface. The definition of this interface can be seen below:</p>
<pre class="literal-block">
interface SplitControl {
<p>An external component MUST call <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> to power a
device on and <tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt> to power a device off. Calls to
either command return one of SUCCESS, FAIL, EBUSY, or
-EALREADY. SUCCESS indicates that the device has now started chaning
-its power mode and it will signal a corresponding completion event in
-the future. EBUSY indicates that the device is in the midst of the
-other operation (e.g., it is starting when stop is called or stopping
+EALREADY. SUCCESS indicates that the device has now started changing
+its power state and will signal a corresponding completion event in
+the future. EBUSY indicates that the device is in the midst of either starting
+or stopping (e.g., it is starting when stop is called or stopping
when start is called) and will not issue an event. EALREADY indicates
-that the device is already in that state; the call is erroneus and a
+that the device is already in that state; the call is erroneous and a
completion event will not be signaled. FAIL indicates that the
device's power state could not be changed. More explicitly:</p>
<p>Successful calls to <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> MUST signal one of
<p>Successful calls to <tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt> MUST signal one of
<tt class="docutils literal"><span class="pre">SplitControl.stopDone(SUCCESS)</span></tt> or <tt class="docutils literal"><span class="pre">SplitControl.stopDone(FAIL)</span></tt>.</p>
<p>Upon signaling a <tt class="docutils literal"><span class="pre">SplitControl.startDone(SUCCESS)</span></tt>, a device MUST
-be completely powered on, and operation requests through calls to commands
+be completely powered on, and operation requests through calls to commands
of other interfaces implemented by the device MAY succeed.</p>
-<p>Upon signalling a <tt class="docutils literal"><span class="pre">SplitControl.stopDone(SUCCESS)</span></tt>, a device MUST be
-completely powered down, and any subsequent calls to commands of other
-interfaces implemented by the device MUST return EOFF or FAIL.</p>
+<p>Upon signalling a <tt class="docutils literal"><span class="pre">SplitControl.stopDone(SUCCESS)</span></tt>, a device MUST be
+completely powered down, and any subsequent calls to commands of other
+interfaces implemented by the device that actually access
+the device hardware MUST return EOFF or FAIL.</p>
<p>If a device is powered on and a successful call to <tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt>
-signals a <tt class="docutils literal"><span class="pre">SplitControl.stopDone(FAIL)</span></tt>, the device MUST still be fully
-powered on, and operation requests through calls to commands of other
+signals a <tt class="docutils literal"><span class="pre">SplitControl.stopDone(FAIL)</span></tt>, the device MUST still be fully
+powered on, and operation requests through calls to commands of other
interfaces implemented by the device MAY succeed.</p>
-<p>If a device is powered down and a successful call to <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt>
-signals a <tt class="docutils literal"><span class="pre">SplitControl.startDone(FAIL)</span></tt>, the device MUST still be fully
-powered down, and operation requests through calls to commands of other
+<p>If a device is powered down and a successful call to <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt>
+signals a <tt class="docutils literal"><span class="pre">SplitControl.startDone(FAIL)</span></tt>, the device MUST still be fully
+powered down, and operation requests through calls to commands of other
interfaces implemented by the device MUST return EOFF or FAIL.</p>
<p>If a device is not able to complete the <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> or
<tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt> requests they MUST return FAIL.</p>
SUCCESS, with the anticipation that a corresponding
<tt class="docutils literal"><span class="pre">SplitControl.startDone()</span></tt> or <tt class="docutils literal"><span class="pre">SplitControl.stopDone()</span></tt>
will be signaled in the future.</p>
-<p>Calls to <cite>SplitControl.start()`</cite> when the device is started
+<p>Calls to <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> when the device is started
or <tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt> while the device is stopped MUST
return EALREADY, indicating that the device is already in that
state. The corresponding completion event (startDone for start
or stopDone for stop) MUST NOT be signaled.</p>
-<p>Calls to <cite>SplitControl.start()`</cite> when the device is stopping or
+<p>Calls to <tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> when the device is stopping or
<tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt> while the device is starting MUST return
EBUSY, indicating that the device is busy performing a differnet
operation. The correspodning completion event (startDone for start or
<col width="15%" />
</colgroup>
<thead valign="bottom">
-<tr><th>Call</th>
-<th>Device On</th>
-<th>Device Off</th>
-<th>Starting</th>
-<th>Stopping</th>
+<tr><th class="head">Call</th>
+<th class="head">Device On</th>
+<th class="head">Device Off</th>
+<th class="head">Starting</th>
+<th class="head">Stopping</th>
</tr>
</thead>
<tbody valign="top">
}
}
</pre>
+<div class="note">
+<p class="first admonition-title">Note</p>
+<p>Other approaches were considered for the return values of
+<tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> and <tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt>. One such
+approach would have replaced EBUSY with SUCCESS when
+<tt class="docutils literal"><span class="pre">SplitControl.start()</span></tt> was called while in the process of stopping
+and <tt class="docutils literal"><span class="pre">SplitControl.stop()</span></tt> was called while in the process of starting.
+However, implementing such an approach adds unwanted complexity to
+a device driver. It is unreasonable to expect the implementor of
+each driver to implement this functionality.</p>
+<p class="last">Returning EBUSY is the most straightforward, unambiguous value
+that can be returned in such a situation. By returning
+EBUSY when a device is in a transitional state, the components
+built on top of a driver unambiguously know exactly why a call to
+<tt class="docutils literal"><span class="pre">start()</span></tt> or <tt class="docutils literal"><span class="pre">stop()</span></tt> did not succeed, and can take action accordingly.
+Since only ONE component should ever implement the <tt class="docutils literal"><span class="pre">SplitControl</span></tt>
+interface for a given device, it isn't unreasonable to expect them
+to keep track of this return value themselves. There is, of course,
+nothing preventing someone from creating a component
+on top of each driver implementation that implements things differently.</p>
+</div>
</div>
-<div class="section" id="power-management-with-asyncstdcontrol">
-<h2><a name="power-management-with-asyncstdcontrol">3.3 Power Management with <tt class="docutils literal"><span class="pre">AsyncStdControl</span></tt></a></h2>
+<div class="section">
+<h2><a id="power-management-with-asyncstdcontrol" name="power-management-with-asyncstdcontrol">3.3 Power Management with <tt class="docutils literal"><span class="pre">AsyncStdControl</span></tt></a></h2>
<p>The commands and the events of the <em>``StdControl``</em> and the <em>``SplitControl``</em>
interfaces are synchronous and can not be called from within
asynchronous code (such as interrupt service routines, etc.). For the
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">The <tt class="docutils literal"><span class="pre">AsyncStdControl</span></tt> interface should be provided whenever it might be
-necessary to allow a device to be powered on or off while running in
-async context. If it is anticipated that a device <em>will</em> not (or more
+necessary to allow a device to be powered on or off while running in
+async context. If it is anticipated that a device <em>will</em> not (or more
likely <em>should</em> not) be powered on or off while in asynchronous context,
-then the <tt class="docutils literal"><span class="pre">StdControl</span></tt> interface SHOULD be provided instead. Components
+then the <tt class="docutils literal"><span class="pre">StdControl</span></tt> interface SHOULD be provided instead. Components
that wish to power the device on or off from within async context would
-then be required to post a task before doing so. In practice,
-<tt class="docutils literal"><span class="pre">AsyncStdControl</span></tt> is provided by low-level hardware resources, while
-<tt class="docutils literal"><span class="pre">StdControl</span></tt> is provided by higher level services built on top of these
+then be required to post a task before doing so. In practice,
+<tt class="docutils literal"><span class="pre">AsyncStdControl</span></tt> is provided by low-level hardware resources, while
+<tt class="docutils literal"><span class="pre">StdControl</span></tt> is provided by higher level services built on top of these
resources.</p>
</div>
</div>
</div>
-<div class="section" id="implicit-power-management">
-<h1><a name="implicit-power-management">4. Implicit Power Management</a></h1>
+<div class="section">
+<h1><a id="implicit-power-management" name="implicit-power-management">4. Implicit Power Management</a></h1>
<p>While explicit power management provides the mechanism for changing
power states, it does not specify a policy.
This does not represent a large problem for the simple case
-of <em>dedicated</em> devices, but can become crucial for non-trivial cases
-involving complex interdependencies between devices controlled by multiple
+of <em>dedicated</em> devices, but can become crucial for non-trivial cases
+involving complex interdependencies between devices controlled by multiple
clients.</p>
-<p>For example, if component <em>A</em> is a client of both component <em>B</em>
+<p>For example, if component <em>A</em> is a client of both component <em>B</em>
and component <em>C</em>, what happens with <em>B</em> and <em>C</em> if
<tt class="docutils literal"><span class="pre">StdControl.stop()</span></tt> is called on component <em>A</em> ? Should components
-<em>B</em> and <em>C</em> also be stopped? What about the reverse case where both
-<em>B</em> and <em>C</em> are clients of the single shared component, <em>A</em>? If
-devices <em>B</em> and <em>C</em> are shut off, should <em>A</em> be shut off as well?
+<em>B</em> and <em>C</em> also be stopped? What about the reverse case where both
+<em>B</em> and <em>C</em> are clients of the single shared component, <em>A</em>? If
+devices <em>B</em> and <em>C</em> are shut off, should <em>A</em> be shut off as well?
How can one decide when it is appropriate to cascade such powerup
and powerdown requests?</p>
<p>The complex nature of the problem is evident from the number of
unexpected behaviors in TinyOS 1.x involving <tt class="docutils literal"><span class="pre">StdControl</span></tt>. On several
platforms, one of the SPI buses is shared between the radio and the
flash device. On some of them, issuing <tt class="docutils literal"><span class="pre">StdControl.stop()</span></tt> on the
-radio results in a series of cascaded calls that result in SPI bus
-becoming disabled, rendering the communication with the flash impossible.
-Of course, the right policy would involve tracking the clients of the
-SPI bus and powering it off only once both the radio and the flash
+radio results in a series of cascaded calls that result in SPI bus
+becoming disabled, rendering the communication with the flash impossible.
+Of course, the right policy would involve tracking the clients of the
+SPI bus and powering it off only once both the radio and the flash
devices were no longer using it. Conversely, the SPI bus should be
powered on whenever there is at least one active client.</p>
-<p>The selection of the right power management policy to use is a complex
-task that depends on the nature of the devices in use, their
-interdependency, as well as on any specific application requirements.
-For cases when some of these features are known a-priori or are
-restricted in some sense, it is preferable that the system provide
-architectural support for enforcing a meaningful <em>default</em> power-management
-policy instead of passing that task on to the application programmer to be
-solved on a case-by-case basis.</p>
-<div class="section" id="power-management-policies">
-<h2><a name="power-management-policies">4.1. Power Management Policies</a></h2>
+<p>The selection of the right power management policy to use is a complex
+task that depends on the nature of the devices in use, their
+interdependency, as well as on any specific application requirements.
+For cases when some of these features are known a-priori or are
+restricted in some sense, it is preferable that the system provide
+architectural support for enforcing a meaningful <em>default</em> power-management
+policy instead of passing that task on to the application programmer to be
+solved on a case-by-case basis. The following section discusses these power
+management policies and the components that implement them in greater detail.</p>
+<div class="section">
+<h2><a id="power-management-policies" name="power-management-policies">4.1. Power Management Policies</a></h2>
<p>Just as generic arbiters are offered in TinyOS 2.x to provide the
arbitration functionality required by shared resources, generic power
management policies are also offered to allow the power management of
-non-virtualised devices to be automatically control.</p>
+non-virtualised devices to be automatically controlled.</p>
<p>Through the use of the arbiter components described in <a class="citation-reference" href="#tep108" id="id6" name="id6">[TEP108]</a>,
device drivers implemented as shared resources provide the type of
restricted resource interdependency where default power-management
<tt class="docutils literal"><span class="pre">ResourceDefaultOwner.granted()</span></tt> event to be signaled in order to
gain ownership over the resource device.</p>
<p>Once it owns the device, the <em>Power Manager</em> is free to execute its
-power-management policy using the StdControl-like interface provided by the
-underlying resource. Different power managers can implement different
+power-management policy using the StdControl-like interface provided by the
+underlying resource. Different power managers can implement different
policies. In the simplest case, this would involve an immediate power-down
-via one of the <tt class="docutils literal"><span class="pre">stop()</span></tt> commands. When the power-state transition
-involves non-negligible costs in terms of wake-up latency or power
-consumption, the <em>PowerManager</em> might revert to a more intelligent
-strategy that tries to reduce these effects. As pointed out in the
-introduction, one such strategy might involve the use of a timer to defer
-the power-down of the resource to some later point in time, giving any
-resource clients a window of opportunity to put in requests before the
+via one of the <tt class="docutils literal"><span class="pre">stop()</span></tt> commands. When the power-state transition
+involves non-negligible costs in terms of wake-up latency or power
+consumption, the <em>PowerManager</em> might revert to a more intelligent
+strategy that tries to reduce these effects. As pointed out in the
+introduction, one such strategy might involve the use of a timer to defer
+the power-down of the resource to some later point in time, giving any
+resource clients a window of opportunity to put in requests before the
device is fully shut down.</p>
-<p>Regardless of the power management policy in use, the <em>Power Manager</em>
-remains owner of the resource as long as the resource is not requested
+<p>Regardless of the power management policy in use, the <em>Power Manager</em>
+remains owner of the resource as long as the resource is not requested
by one of its clients. Whenever a client puts in a request, the
-<em>Power Manager</em> will receive a <tt class="docutils literal"><span class="pre">ResourceDefaultOwner.requested()</span></tt> event
-(or <tt class="docutils literal"><span class="pre">immediateRequested()</span></tt> event) from the arbiter it is associated with.
-Upon receiving this event, the <em>Power Manager</em> MUST power up the
+<em>Power Manager</em> will receive a <tt class="docutils literal"><span class="pre">ResourceDefaultOwner.requested()</span></tt> event
+(or <tt class="docutils literal"><span class="pre">immediateRequested()</span></tt> event) from the arbiter it is associated with.
+Upon receiving this event, the <em>Power Manager</em> MUST power up the
resource through the StdControl-like interface provided by the lower level
-abstraction of the physical device. The <em>Power Manager</em> SHOULD release the
+abstraction of the physical device. The <em>Power Manager</em> MUST release the
ownership of the resource (using the <tt class="docutils literal"><span class="pre">ResourceDefaultOwner.release()</span></tt>
-command) but MUST wait until after the resource has been fully powered on
+command) and MUST wait until after the resource has been fully powered on
before doing so.</p>
<p>Modeling devices as shared resources and allowing them to be
controlled in the way described here, solves the problems outlined in
events answers the question of when. As long as the resource at
the bottom of a large set of nested resource clients has been fully released,
the power mananger will be able to power down the resource appropriately.</p>
-<p>Using the model described above, a resource that uses one of these policies
+<p>Using the model described above, a resource that uses one of these policies
according to the <em>implicitly power management</em> model could be built as shown below:</p>
<pre class="literal-block">
module MyFlashP {
provides {
interface Init;
interface SplitControl;
- interface Resource;
- interface FlashCommands;
- ...
+ interface Resource;
+ interface FlashCommands;
+ ...
}
}
implementation {
...
-}
+}
generic module PowerManagerC(uint8_t POWERDOWN_DELAY) {
provides {
- interface Init;
+ interface Init;
}
uses {
- interface SplitControl;
- interface ResourceDefaultOwner;
+ interface SplitControl;
+ interface ResourceDefaultOwner;
}
}
implementation {
#define MYFLASH_POWERDOWN_DELAY 1000
configuration MyFlashC {
provides {
- interface Init;
- interface Resource;
- interface FlashCommands;
+ interface Init;
+ interface Resource;
+ interface FlashCommands;
}
}
implementation {
components new PowerManagerC(MYFLASH_POWERDOWN_DELAY)
- , FcfsArbiter(MYFLASH_RESOURCE)
- , MyFlashP;
+ , FcfsArbiter(MYFLASH_RESOURCE)
+ , MyFlashP;
Init = MyFlashP;
- Resource = FcfsArbiter;
+ Resource = FcfsArbiter;
FlashCommands = MyFlashP;
PowerManagerC.ResourceDefaultUser -> FcfsArbiter;
PowerManagerC.SplitControl -> MyFlashP;
-
+
}
</pre>
<p>This example implementation is built out of three components. The
components, as well as an arbiter component for managing shared clients
of the device. Notice how the <em>Power Manager</em> is wired to both the
<tt class="docutils literal"><span class="pre">ResourceDefaultUser</span></tt> interface provided by the arbiter, and the
-<tt class="docutils literal"><span class="pre">SplitControl</span></tt> interface provided by the flash. All clients of this flash
+<tt class="docutils literal"><span class="pre">SplitControl</span></tt> interface provided by the flash. All clients of this flash
device are directly connected to the resource interface provided by
the arbiter. As outlined above, the <tt class="docutils literal"><span class="pre">PowerManagerC</span></tt> component will use
-the events signaled through the <tt class="docutils literal"><span class="pre">ResourceDefaultUser</span></tt> interface to determine
+the events signaled through the <tt class="docutils literal"><span class="pre">ResourceDefaultUser</span></tt> interface to determine
when to make calls to power the device up and power it down through
the <tt class="docutils literal"><span class="pre">SplitControl</span></tt> interface.</p>
</div>
-<div class="section" id="example-power-managers-powermanagerc-and-deferredpowermanagerc">
-<h2><a name="example-power-managers-powermanagerc-and-deferredpowermanagerc">4.2. Example Power Managers: PowerManagerC and DeferredPowerManagerC</a></h2>
+<div class="section">
+<h2><a id="example-power-managers-powermanagerc-and-deferredpowermanagerc" name="example-power-managers-powermanagerc-and-deferredpowermanagerc">4.2. Example Power Managers: PowerManagerC and DeferredPowerManagerC</a></h2>
<p>TinyOS 2.x currently has two default power management policies
-that it provides. These policies are implemented by the various
-components located under tinyos-2.x/lib/power. The first policy
+that it provides. These policies are implemented by the various
+components located under tinyos-2.x/lib/power. The first policy
is implemented using an <em>immediate</em> power control scheme, whereby
devices are powered on and off immediately after they have been
requested and released. The second policy is implemented using
-a <em>deferred</em> power control scheme, whereby devices are powered
+a <em>deferred</em> power control scheme, whereby devices are powered
on immediately after being requested, but powered off after
-some small delay from being released.</p>
-<p>Each policy has three different implementations for use by each of
+some small delay from being released. This delay is configurable
+to meet the varying needs of different device drivers.</p>
+<p>Each policy has three different implementations for use by each of
the <tt class="docutils literal"><span class="pre">StdControl</span></tt>, <tt class="docutils literal"><span class="pre">SplitControl</span></tt>, and <tt class="docutils literal"><span class="pre">AsyncStdControl</span></tt>
interfaces.</p>
<p>For reference, each of the available components are listed below</p>
</dl>
</div>
</div>
-<div class="section" id="author-s-address">
-<h1><a name="author-s-address">5. Author's Address</a></h1>
+<div class="section">
+<h1><a id="author-s-address" name="author-s-address">5. Author's Address</a></h1>
<div class="line-block">
<div class="line">Kevin Klues</div>
-<div class="line">503 Bryan Hall</div>
-<div class="line">Washington University</div>
-<div class="line">St. Louis, MO 63130</div>
+<div class="line">444 Gates Hall</div>
+<div class="line">Stanford University</div>
+<div class="line">Stanford, CA 94305-9030</div>
<div class="line"><br /></div>
-<div class="line">phone - +1-314-935-6355</div>
-<div class="line">email - <a class="reference" href="mailto:klueska@cs.wustl.edu">klueska@cs.wustl.edu</a></div>
+<div class="line">email - <a class="reference" href="mailto:klueska@cs.stanford.edu">klueska@cs.stanford.edu</a></div>
<div class="line"><br /></div>
<div class="line">Vlado Handziski</div>
<div class="line">Sekr FT5</div>
<div class="line">Stanford, CA 94305-9030</div>
<div class="line"><br /></div>
<div class="line">phone - +1 650 725 9046</div>
-<div class="line">email - <a class="reference" href="mailto:pal@cs.stanford.edu">pal@cs.stanford.edu</a> </div>
+<div class="line">email - <a class="reference" href="mailto:pal@cs.stanford.edu">pal@cs.stanford.edu</a></div>
</div>
</div>
-<div class="section" id="citations">
-<h1><a name="citations">6. Citations</a></h1>
+<div class="section">
+<h1><a id="citations" name="citations">6. Citations</a></h1>
<table class="docutils citation" frame="void" id="tep102" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
projects / tinyos-2.x.git / blobdiff