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Documents stop_arg!=0 when stop_src=TRIG_NONE 

This patch documents the new interpretation of stop_arg when stop_src ==
TRIG_NONE.  In the new interpretation, if stop_src==TRIG_NONE, a user may
specify that a buffer of finite length (and less than or equal to the
maximum buffer size) be repeated indefinitely.

For now, only the NI MIO driver implements this new interpretation.  All
other drivers should continue to force stop_arg==0 when
stop_src==TRIG_NONE.  In this case, the old behavior is maintained.
This commit is contained in:
Spencer E. Olson 2016-03-08 22:47:52 -07:00
parent ea09b60196
commit 3f19af6b53
1 changed files with 9 additions and 4 deletions
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13
doc/other.xml
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@ -1090,10 +1090,15 @@ until stopped using
<function><link linkend="func-ref-comedi-cancel">comedi_cancel</link></function>.
</para>
<para>
Its <structfield>stop_arg</structfield> argument is reserved and should be set to <literal>0</literal>.
(<quote>Reserved</quote>
means that unspecified things could happen if it is set to something
else but <literal>0</literal>.)
<structfield>stop_arg</structfield> is used to denote how many samples should be
used in the continuous acquisition. If <structfield>stop_arg</structfield> is
set to <literal>0</literal>, the entire output buffer may contribute to the
output. If <structfield>stop_arg</structfield> != <literal>0</literal>, only
the memory for <structfield>stop_arg</structfield> samples will be used. Many
drivers do not yet support
<structfield>stop_arg</structfield>!=<literal>0</literal> and should enforce
<structfield>stop_arg</structfield>=<literal>0</literal> via
comedi_command_test.
</para>
</listitem>