xnu-7195.101.1.tar.gz

[apple/xnu.git] / osfmk / man / clock_set_attributes.html

<h2>clock_set_attributes</h2>
<hr>
<p>
<strong>Function</strong> - Set a particular clock's attributes.
<h3>SYNOPSIS</h3>
<pre>
<strong>kern_return_t   clock_set_attributes</strong>
                <strong>(clock_ctrl_t</strong>                     <var>clock_control</var>,
                 <strong>clock_flavor_t</strong>                          <var>flavor</var>,
                 <strong>clock_attr_t</strong>                         <var>attribute</var>,
                 <strong>clock_control</strong>                  <var>attribute_count</var><strong>);</strong>
</pre>
<h3>PARAMETERS</h3>
<dl>
<p>
<dt> <var>clock_control</var> 
<dd>
[in clock-control send right]
The control port for the clock.
<p>
<dt> <var>flavor</var> 
<dd>
[in scalar]
Type of information to be set.  Defined values are:
<dl>
<p>
<dt> <strong>CLOCK_ALARM_CURRES</strong>
<dd>
The resolution, in nanoseconds, at which clock alarm and 
sleep timers are currently serviced.  Increasing the current
resolution will have no impact on any pending clock alarms (i.e. 
they will go off as originally scheduled).  Decreasing the
current resolution will truncate any pending alarms to the
granularity of the new current resolution.  This value must be a 
multiple of the minimum resolution and not greater than the 
maximum resolution of the clock.
</dl>
<p>
<dt> <var>attribute</var> 
<dd>
[pointer to in scalar]
New attribute.
<p>
<dt> <var>attribute_count</var> 
<dd>
[in scalar]
The size of the buffer (in natural-sized units).
</dl>
<h3>DESCRIPTION</h3>
<p>
The <strong>clock_set_attributes</strong> function sets attributes of
a clock's operation.
<h3>NOTES</h3>
<p>
The main reason a clock's current resolution would not always equal its
minimum resolution is because the overhead of sustaining the
minimum resolution, 
when it is not needed by any existing alarm service client, may be prohibitive 
for a given hardware platform and underlying clock device.
<h3>RETURN VALUES</h3>
<p>
Only generic errors apply.
<h3>RELATED INFORMATION</h3>
<p>
Functions:
<a href="host_get_clock_control.html"><strong>host_get_clock_control</strong></a>,
<a href="clock_set_time.html"><strong>clock_set_time</strong></a>,
<a href="clock_get_attributes.html"><strong>clock_get_attributes</strong></a>.