Lines Matching +full:segment +full:- +full:1 +full:a
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19 <!-- #BeginDate format:En2m -->8-Aug-2014 19:17<!-- #EndDate -->
28 <p>This driver receives its reference clock info from a shared
29 memory-segment. The shared memory-segment is created with owner-only
31 ≥2. Units 0 and 1 are always created with owner-only access for
36 <h4>Structure of shared memory-segment</h4>
38 int mode; /* 0 - if valid is set:
41 * 1 - if valid is set:
61 <p>Each second, the value of <code>valid</code> of the shared memory-segment is checked:</p>
64 <h4>Operation mode=1</h4>
65 <p>Each second, <code>valid</code> in the shared memory-segment is checked:</p>
69 <h4>Mode-independent post-processing</h4>
71 segment, some sanity checks take place:
79 set to 1.
84 <a href="http://gpsd.berlios.de/"><i>GPSD</i></a>
90 The SHM driver was fixed (ntp-4.2.5p138) to collect data each second rather than
99 available. Receivers with a loose/sloppy timing between PPS and serial data
106 If flag4 is set when the driver is polled, a clockstats record is written.
113 …e 8th field is the number of times the the mode 1 info was update while <i>NTPD</i> was trying to …
116 Here is a sample showing the GPS reception fading out:
118 54364 84927.157 127.127.28.0 66 65 1 0 0
121 54364 85116.159 127.127.28.0 63 62 1 0 0
122 54364 85180.158 127.127.28.0 64 63 1 0 0
141 <table border="1" width="100%">
152 <td align="center">1</td>
153 <td align="center">1</td>
154 <td>The SHM segment is private (mode 0600). This is the fixed
155 default for clock units 0 and 1; clock units >1 are mode
158 <td align="center">1-31</td>
159 <td align="center">-</td>
160 <td align="center">-</td>
161 <td><i>reserved -- do not use</i></td>
173 default value of 4hrs (14400s) is used instead. See also flag 1.
178 <dt><tt>flag1 0 | 1</tt>
182 to force long-distance initial jumps. <i>Check</i> the
184 <dt><tt>flag2 0 | 1</tt>
186 <dt><tt>flag3 0 | 1</tt>
188 <dt><tt>flag4 0 | 1</tt>
194 <p>The driver attempts to create a shared memory segment with an
196 a numeric value or a string) clearly depends on the method used, which
201 <tt>Windows</tt> uses a file mapping to the page file with the
204 non-public mappings are created as
207 Public access assigns a NULL DACL to the memory mapping, while
213 <tt>SYSV IPC</tt> creates a shared memory segment with a key value
215 the clock unit. (This value could be hex-decoded as 'NTP0',
218 Public access means a permission set of 0666, while private access
219 creates the mapping with a permission set of 0600.
226 <p><i>NTPD</i> is started as root on most POSIX-like operating systems
230 clock setup. The actual polling of the clock is done as the run-time
231 user; deferring the creation of the SHM segment to this point will
232 create a SHM segment owned by the runtime-user account. The internal
233 structure of <i>NTPD</i> does not permit the use of a fudge flag if
234 this is to be avoided; this is the reason why a mode bit is used for
235 the configuration of a public segment.
239 create a SHM segment in the global object name space for SHM clocks with
246 <p><a href="../refclock.html">Reference Clock Drivers</a></p>