doc: tweak some of the documentation for streaming acquisition functions
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1 changed files with 71 additions and 48 deletions
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@ -11,8 +11,8 @@ Description:
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on the subdevice indicated by the parameters <parameter class="function">device</parameter>
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and <parameter class="function">subdevice</parameter>.
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Returns:
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If successful, <literal>0</literal> is returned, otherwise
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<literal>-1</literal>.
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On success, <literal>0</literal> is returned.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_command -- start streaming input/output
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Retval: int
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@ -33,8 +33,8 @@ Description:
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For output subdevices,
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sample values are written using the function <function>write</function>.
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Returns:
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If successful, <literal>0</literal> is returned, otherwise
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<literal>-1</literal>.
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On success, <literal>0</literal> is returned.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_command_test -- test streaming input/output configuration
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Retval: int
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@ -48,7 +48,7 @@ Description:
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of the <type>comedi_cmd</type> structure are invalid, they may be modified. Source
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elements are modified to remove invalid source triggers. Argument
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elements are adjusted or rounded to the nearest valid value.
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Returns:
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The meanings of the return value are as follows:
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<itemizedlist>
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@ -101,7 +101,8 @@ Description:
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use the same input range.
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</para>
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</listitem>
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</itemizedlist>
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</itemizedlist>
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_buffer_contents -- streaming buffer status
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Retval: int
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@ -109,9 +110,14 @@ Param: comedi_t * device
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Param: unsigned int subdevice
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Description:
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The function <function>comedi_get_buffer_contents</function> is used on a subdevice
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that has a Comedi command in progress. The number of bytes that
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are available in the streaming buffer is returned. If there is
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an error, <literal>-1</literal> is returned.
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that has a Comedi command in progress to get the number of unread bytes. For
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a streaming input command, this is the number of bytes that can be read. For
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a streaming output command, subtracting this from the buffer size gives the
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space available to be written.
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Returns:
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On success, <function>comedi_get_buffer_contents</function> returns the
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number of unread bytes in the buffer.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_buffer_offset -- streaming buffer status
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Retval: int
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@ -119,10 +125,14 @@ Param: comedi_t * device
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Param: unsigned int subdevice
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Description:
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The function <function>comedi_get_buffer_offset</function> is used on a subdevice
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that has a Comedi command in progress. This function returns
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the offset in bytes of the read pointer in the streaming buffer.
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that has a Comedi command in progress to get the current read position in the
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streaming buffer as an offset in bytes from the start of the buffer.
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The position will wrap around to 0 when it reaches the buffer size.
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This offset is only useful for memory mapped buffers.
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If there is an error, <literal>-1</literal> is returned.
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Returns:
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On success, <function>comedi_get_buffer_offset</function> returns the current
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read position as an offset in bytes from the start of the buffer.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_buffer_size -- streaming buffer size of subdevice
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Retval: int
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@ -133,7 +143,10 @@ Description:
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of the streaming buffer for the subdevice specified by
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<parameter class="function">device</parameter> and
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<parameter class="function">subdevice</parameter>.
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On error, <literal>-1</literal> is returned.
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Returns:
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On success, <function>comedi_get_buffer_size</function> returns the size of
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the buffer in bytes.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_cmd_generic_timed -- streaming input/output capabilities
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Retval: int
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@ -162,8 +175,8 @@ Description:
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The rate is adjusted to a rate that the device
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can handle.
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Returns:
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If successful, <literal>0</literal> is returned, otherwise
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<literal>-1</literal>.
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On success, <literal>0</literal> is returned.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_cmd_src_mask -- streaming input/output capabilities
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Retval: int
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@ -180,8 +193,8 @@ Description:
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of the subdevice's supported trigger sources. Other elements in the structure
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are undefined.
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Returns:
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If successful, <literal>0</literal> is returned, otherwise
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<literal>-1</literal>.
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On success, <literal>0</literal> is returned.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_max_buffer_size -- maximum streaming buffer size
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Retval: int
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@ -197,7 +210,11 @@ Description:
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<function><link
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linkend="func-ref-comedi-set-max-buffer-size">comedi_set_max_buffer_size</link></function>
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or with the <command>comedi_config</command> program,
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and requires appropriate privileges. On error, <literal>-1</literal> is returned.
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and requires appropriate privileges.
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Returns:
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On success, the maximum allowable size (in bytes) of the streaming buffer
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is returned.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_read_subdevice -- find streaming input subdevice
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Retval: int
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@ -206,8 +223,12 @@ Description:
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The function <function>comedi_get_read_subdevice</function> returns the
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index of the subdevice
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whose streaming input buffer is currently accessible through the
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device <parameter class="function">device</parameter>. If
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there is no such subdevice, <literal>-1</literal> is returned.
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device <parameter class="function">device</parameter>, if there is one.
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Returns:
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On success, <function>comedi_get_read_subdevice</function>returns the index
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of the current <quote>read</quote> subdevice if there is one,
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or <literal>-1</literal> if there is no <quote>read</quote> subdevice.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_get_write_subdevice -- find streaming output subdevice
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Retval: int
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@ -216,8 +237,12 @@ Description:
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The function <function>comedi_get_write_subdevice</function> returns the
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index of the subdevice
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whose streaming output buffer is currently accessible through the
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device <parameter class="device">device</parameter>. If there is no such subdevice,
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<literal>-1</literal> is returned.
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device <parameter class="device">device</parameter>, if there is one.
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Returns:
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On success, <function>comedi_get_write_subdevice</function>returns the index
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of the current <quote>write</quote> subdevice if there is one,
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or <literal>-1</literal> if there is no <quote>write</quote> subdevice.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_mark_buffer_read -- streaming buffer control
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Retval: int
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@ -236,15 +261,10 @@ Description:
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bytes in the buffer
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are no longer needed and may be discarded.
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Returns:
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The function <function>comedi_mark_buffer_read</function> returns the
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number of bytes successfully marked as read,
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or <literal>-1</literal> on error. The return value may be less than
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<parameter class="function">num_bytes</parameter> if you attempt to mark more
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bytes read than are currently available for reading, or
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if <parameter class="function">num_bytes</parameter> must be rounded down
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to be an exact multiple of the subdevice's
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sample size (either <code language="C">sizeof(sampl_t)</code> or
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<code language="C">sizeof(lsampl_t)</code>).
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On success, <function>comedi_mark_buffer_read</function> returns the
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number of bytes successfully marked as read. The return value may be less than
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the <parameter class="function">num_bytes</parameter>.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_mark_buffer_written -- streaming buffer control
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Retval: int
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bytes in the buffer
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are valid and may be sent to the device.
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Returns:
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The function <function>comedi_mark_buffer_written</function> returns
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number of bytes successfully marked as written,
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or <literal>-1</literal> on error. The return value may be less than
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<parameter class="function">num_bytes</parameter> if you attempt to mark more
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bytes written than the amount of free space currently available
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in the output buffer, or
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if <parameter class="function">num_bytes</parameter> must be
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rounded down to be an exact multiple of the subdevice's
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sample size (either <code language="C">sizeof(sampl_t)</code>
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or <code language="C">sizeof(lsampl_t)</code>).
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On success, <function>comedi_mark_buffer_written</function> returns the
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number of bytes successfully marked as written. The return value may be less than
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the <parameter class="function">num_bytes</parameter>.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_poll -- force updating of streaming buffer
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Retval: int
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Comedi command in progress in order to update the streaming buffer.
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If supported by the driver, all available samples are copied to
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the streaming buffer. These samples may be pending in DMA buffers
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or device FIFOs. If successful, the number of additional bytes
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available is returned. If there is an error, <literal>-1</literal> is returned.
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or device FIFOs.
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Only a few Comedi drivers support this operation.
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Returns:
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On success, <function>comedi_poll</function> returns the number of additional
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bytes available.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_set_buffer_size -- streaming buffer size of subdevice
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Retval: int
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linkend="func-ref-comedi-set-max-buffer-size">comedi_set_max_buffer_size</link></function>,
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or running the program <command>comedi_config</command>.
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Returns:
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The new buffer size in bytes is returned on success. On error,
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<literal>-1</literal> is returned.
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On success, <function>comedi_set_buffer_size</function> returns the new
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buffer size in bytes.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_set_max_buffer_size -- streaming maximum buffer size of subdevice
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Retval: int
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<parameter class="function">subdevice</parameter>. Changing the maximum buffer
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size requires the user to have appropriate privileges.
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Returns:
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The new maximum buffer size is returned on success. On error, <literal>-1</literal> is returned.
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On success, <function>comedi_set_max_buffer_size</function> returns the new
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maximum buffer size in bytes.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_set_read_subdevice -- set streaming input subdevice
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Retval: int
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<parameter class="function">device</parameter> and have no effect on other
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open file descriptions for the underlying device node.
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Returns:
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<literal>0</literal> on success, <literal>-1</literal> on error.
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On success, <literal>0</literal> is returned.
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On failure, <literal>-1</literal> is returned.
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Function: comedi_set_write_subdevice -- set streaming output subdevice
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Retval: int
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<parameter class="function">device</parameter> and have no effect on other
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open file descriptions for the underlying device node.
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Returns:
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<literal>0</literal> on success, <literal>-1</literal> on error.
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On success, <literal>0</literal> is returned.
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On failure, <literal>-1</literal> is returned.
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