+Asynchronous commands
Function: comedi_cancel -- stop streaming input/output in progress
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Description:
- The function comedi_cancel() can be used to stop a command
+ The function <function>comedi_cancel</function> can be used to stop a command
previously started by
- <link linkend="func-ref-comedi-command"><function>comedi_command</function></link>
+ <function><link linkend="func-ref-comedi-command">comedi_command</link></function>
which is still in progress
- on the subdevice indicated by the parameters <parameter>device</parameter>
- and <parameter>subdevice</parameter>.
+ on the subdevice indicated by the parameters <parameter class="function">device</parameter>
+ and <parameter class="function">subdevice</parameter>.
Returns:
- If successful, 0 is returned, otherwise -1.
+ If successful, <literal>0</literal> is returned, otherwise
+ <literal>-1</literal>.
Function: comedi_command -- start streaming input/output
Retval: int
Param: comedi_t * device
Param: comedi_cmd * command
Description:
- The function comedi_command() starts streaming input or output. The
- command structure pointed to by the parameter command specifies the
- acquisition. The command must be able to pass comedi_command_test()
- with a return value of 0, or comedi_command() will fail.
+ The function <function>comedi_command</function> starts a streaming input
+ or output. The
+ command structure pointed to by <parameter class="function">command</parameter> specifies
+ settings for the
+ acquisition. The command must be able to pass
+ <function><link
+ linkend="func-ref-comedi-command-test">comedi_command_test</link></function>
+ with a return value of <literal>0</literal>, or
+ <function>comedi_command</function> will fail.
For input subdevices, sample values are read using the
- function read(). For output subdevices, sample values are written
- using the function write().
-
- If successful, 0 is returned, otherwise -1.
+ function <function>read</function> on the device file. For output subdevices,
+ sample values are written using the function <function>write</function>.
+Returns:
+ If successful, <literal>0</literal> is returned, otherwise
+ <literal>-1</literal>.
Function: comedi_command_test -- test streaming input/output configuration
Retval: int
Param: comedi_t * device
Param: comedi_cmd * command
Description:
- The function comedi_command_test() tests the command structure pointed
- to by the parameter command and returns an integer describing the
+ The function <function>comedi_command_test</function> tests the command structure pointed
+ to by the parameter <parameter class="function">command</parameter> and returns an
+ integer describing the
testing stages that were successfully passed. In addition, if elements
- of the command structure are invalid, they may be modified. Source
+ of the <type>comedi_cmd</type> structure are invalid, they may be modified. Source
elements are modified to remove invalid source triggers. Argument
elements are adjusted or rounded to the nearest valid value.
- The meanings of the return value are as follows.
-
- 0 indicates a valid command.
-
- 1 indicates that one of the *_src
- members of the command contained an
- unsupported trigger. The bits corresponding to the unsupported
- triggers are zeroed.
-
- 2 indicates that the particular combination
- of *_src settings is not supported by the driver, or that
- one of the *_src members has the bit corresponding to
- multiple trigger sources set at the same time.
-
- 3 indicates that one of the *_arg members
- of the command is set outside the range of allowable values.
- For instance, an argument for a TRIG_TIMER source which
- exceeds the board's maximum speed. The invalid *_arg
- members will be adjusted to valid values.
+ The meanings of the return value are as follows:
- 4 indicates that one of the *_arg members
- required adjustment. For instance, the argument of a
- TRIG_TIMER source may have been rounded to the nearest
- timing period supported by the board.
-
- 5 indicates that some aspect of the
- command's chanlist is unsupported by the board. For example,
- some board's require that all channels in the chanlist
- use the same range.
+ <itemizedlist>
+ <listitem>
+ <para><literal>0</literal> indicates a valid command.</para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>1</literal> indicates that one of the
+ <structfield>…_src</structfield>
+ members of the command contained an
+ unsupported trigger. The bits corresponding to the unsupported
+ triggers are zeroed.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>2</literal> indicates that the particular combination
+ of <structfield>…_src</structfield> settings is not supported by the driver, or that
+ one of the <structfield>…_src</structfield> members has the bit corresponding to
+ multiple trigger sources set at the same time.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>3</literal> indicates that one of the
+ <structfield>…_arg</structfield> members
+ of the command is set outside the range of allowable values.
+ For instance, an argument for a
+ <constant>TRIG_TIMER</constant> source which
+ exceeds the board's maximum speed. The invalid
+ <structfield>…_arg</structfield>
+ members will be adjusted to valid values.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>4</literal> indicates that one of the
+ <structfield>…_arg</structfield> members
+ required adjustment. For instance, the argument of a
+ <constant>TRIG_TIMER</constant> source may have been rounded to the nearest
+ timing period supported by the board.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>5</literal> indicates that some aspect of the
+ command's <structfield>chanlist</structfield> is unsupported by the board. For example,
+ some analog input boards require that all channels in the chanlist
+ use the same input range.
+ </para>
+ </listitem>
+ </itemizedlist>
Function: comedi_get_buffer_contents -- streaming buffer status
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Description:
- The function comedi_get_buffer_contents() is used on a subdevice
+ The function <function>comedi_get_buffer_contents</function> is used on a subdevice
that has a Comedi command in progress. The number of bytes that
are available in the streaming buffer is returned. If there is
- an error, -1 is returned.
+ an error, <literal>-1</literal> is returned.
Function: comedi_get_buffer_offset -- streaming buffer status
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Description:
- The function comedi_get_buffer_offset() is used on a subdevice
+ The function <function>comedi_get_buffer_offset</function> is used on a subdevice
that has a Comedi command in progress. This function returns
the offset in bytes of the read pointer in the streaming buffer.
This offset is only useful for memory mapped buffers.
- If there is an error, -1 is returned.
+ If there is an error, <literal>-1</literal> is returned.
Function: comedi_get_buffer_size -- streaming buffer size of subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Description:
- The function comedi_get_buffer_size() returns the size (in bytes)
- of the streaming buffer for the subdevice specified by device and
- subdevice. On error, -1 is returned.
+ The function <function>comedi_get_buffer_size</function> returns the size (in bytes)
+ of the streaming buffer for the subdevice specified by
+ <parameter class="function">device</parameter> and
+ <parameter class="function">subdevice</parameter>.
+ On error, <literal>-1</literal> is returned.
Function: comedi_get_cmd_generic_timed -- streaming input/output capabilities
Retval: int
Param: unsigned int scan_period_ns
Description:
The command capabilities of the subdevice indicated by the parameters
- device and subdevice are probed, and the results placed in the
- command structure pointed to by the parameter command. The command
- structure pointed to by the parameter command is modified to be a
- valid command that can be used as a parameter to comedi_command()
- (after the command has been assigned a valid chanlist array).
- The command measures scans consisting of chanlist_len channels
- at a scan rate that corresponds to the
- period scan_period_ns. The rate is adjusted to a rate that the device
- can handle. If successful, 0 is returned, otherwise -1.
+ <parameter class="function">device</parameter> and <parameter
+ class="function">subdevice</parameter>
+ are probed, and the results placed in the
+ command structure pointed to by the parameter <parameter
+ class="function">command</parameter>.
+ The command structure pointed to by <parameter class="function">command</parameter>
+ is modified to be a
+ valid command that can be used as a parameter to
+ <function><link linkend="func-ref-comedi-command">comedi_command</link></function>
+ (after the command has additionally been assigned a valid
+ <structfield>chanlist</structfield> array).
+ The command measures scans consisting of <parameter class="function">chanlist_len</parameter>
+ channels
+ at a scan rate that corresponds to a period of
+ <parameter class="function">scan_period_ns</parameter> nanoseconds.
+ The rate is adjusted to a rate that the device
+ can handle.
+Returns:
+ If successful, <literal>0</literal> is returned, otherwise
+ <literal>-1</literal>.
Function: comedi_get_cmd_src_mask -- streaming input/output capabilities
Retval: int
Param: comedi_cmd * command
Description:
The command capabilities of the subdevice indicated by the parameters
- device and subdevice are probed, and the results placed in the
- command structure pointed to by the parameter command. The trigger
- source elements of the command structure are set to the logical OR
- value of possible trigger sources. Other elements in the structure
- are undefined. If successful, 0 is returned, otherwise -1.
+ <parameter class="function">device</parameter> and <parameter
+ class="function">subdevice</parameter>
+ are probed, and the results placed in the
+ command structure pointed to by <parameter class="function">command</parameter>. The trigger
+ source elements of the command structure are set to be the bitwise-or
+ of the subdevice's supported trigger sources. Other elements in the structure
+ are undefined.
+Returns:
+ If successful, <literal>0</literal> is returned, otherwise
+ <literal>-1</literal>.
Function: comedi_get_max_buffer_size -- maximum streaming buffer size
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Description:
- The function comedi_get_max_buffer_size() returns the maximum
+ The function <function>comedi_get_max_buffer_size</function> returns the maximum
allowable size (in bytes) of the streaming buffer for the subdevice
- specified by device and subdevice. Changing the maximum buffer
- size requires appropriate privileges. On error, -1 is returned.
+ specified by <parameter class="function">device</parameter>
+ and <parameter class="function">subdevice</parameter>.
+ Changing the maximum buffer
+ size can be accomplished with
+ <function><link
+ linkend="func-ref-comedi-set-max-buffer-size">comedi_set_max_buffer_size</link></function>
+ or with the <command>comedi_config</command> program,
+ and requires appropriate privileges. On error, <literal>-1</literal> is returned.
Function: comedi_get_read_subdevice -- find streaming input subdevice
Retval: int
Param: comedi_t * device
Description:
- The function comedi_get_read_subdevice() returns the subdevice
- that allows streaming input for device dev. If no subdevice
- supports streaming input, -1 is returned and the Comedilib error
- number is set to XXX "subdevice not found".
+ The function <function>comedi_get_read_subdevice</function> returns the
+ index of the subdevice
+ whose streaming input buffer is accessible through the
+ device <parameter class="function">device</parameter>. If
+ there is no such subdevice, <literal>-1</literal> is returned.
Function: comedi_get_write_subdevice -- find streaming output subdevice
Retval: int
Param: comedi_t * device
Description:
- The function comedi_get_write_subdevice() returns the subdevice
- that allows streaming output for device dev. If no subdevice
- supports streaming output, -1 is returned and the Comedilib error
- number is set to XXX "subdevice not found".
+ The function <function>comedi_get_write_subdevice</function> returns the
+ index of the subdevice
+ whose streaming output buffer is accessible through the
+ device <parameter class="device">device</parameter>. If there is no such subdevice,
+ <literal>-1</literal> is returned.
Function: comedi_mark_buffer_read -- streaming buffer control
Retval: int
Param: unsigned int subdevice
Param: unsigned int num_bytes
Description:
- The function comedi_mark_buffer_read() is used on a subdevice
+ The function <function>comedi_mark_buffer_read</function> is used on a subdevice
that has a Comedi input command in progress. It should only be used
- if you are using a mmap() (as opposed
- to calling read() on the device file) to read data from Comedi's buffer,
+ if you are using a <function>mmap</function> mapping to read data from Comedi's buffer
+ (as opposed to calling <function>read</function> on the device file),
since Comedi will automatically keep track of how many bytes have been
- transferred via read() calls. This function is
- used to indicate that the next num_bytes bytes in the buffer
+ transferred via <function>read</function> calls. This function is
+ used to indicate that the next <parameter class="function">num_bytes</parameter>
+ bytes in the buffer
are no longer needed and may be discarded.
Returns:
- A return value ret greater than 0 indicates that the read offset in
- the streaming buffer, as returned by comedi_get_buffer_offset, has been
- incremented by ret bytes. If there is an error, -1 is returned.
+ The function <function>comedi_mark_buffer_read</function> returns the
+ number of bytes successfully marked as read,
+ or <literal>-1</literal> on error. The return value may be less than
+ <parameter class="function">num_bytes</parameter> if you attempt to mark more
+ bytes read than are currently available for reading, or
+ if <parameter class="function">num_bytes</parameter> must be rounded down
+ to be an exact multiple of the subdevice's
+ sample size (either <code language="C">sizeof(sampl_t)</code> or
+ <code language="C">sizeof(lsampl_t)</code>).
Function: comedi_mark_buffer_written -- streaming buffer control
Retval: int
Param: unsigned int subdevice
Param: unsigned int num_bytes
Description:
- The function comedi_mark_buffer_written() is used on a subdevice
+ The function <function>comedi_mark_buffer_written</function> is used on a subdevice
that has a Comedi output command in progress. It should only be used
- if you are using a mmap() (as opposed to calling write() on the device
- file) to write data to Comedi's buffer, since Comedi
+ if you are using a <function>mmap</function> mapping to write data to Comedi's buffer
+ (as opposed to calling <function>write</function> on the device
+ file), since Comedi
will automatically keep track of how many bytes have been
- transferred via write() calls. This function is
- used to indicate that the next num_bytes bytes in the buffer
+ transferred via <function>write</function> calls. This function is
+ used to indicate that the next <parameter class="function">num_bytes</parameter>
+ bytes in the buffer
are valid and may be sent to the device.
- If there is an error, -1 is returned.
+Returns:
+ The function <function>comedi_mark_buffer_written</function> returns
+ number of bytes successfully marked as written,
+ or <literal>-1</literal> on error. The return value may be less than
+ <parameter class="function">num_bytes</parameter> if you attempt to mark more
+ bytes written than the amount of free space currently available
+ in the output buffer, or
+ if <parameter class="function">num_bytes</parameter> must be
+ rounded down to be an exact multiple of the subdevice's
+ sample size (either <code language="C">sizeof(sampl_t)</code>
+ or <code language="C">sizeof(lsampl_t)</code>).
Function: comedi_poll -- force updating of streaming buffer
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Description:
- The function comedi_poll() is used on a subdevice that has a
+ The function <function>comedi_poll</function> is used on a subdevice that has a
Comedi command in progress in order to update the streaming buffer.
If supported by the driver, all available samples are copied to
the streaming buffer. These samples may be pending in DMA buffers
or device FIFOs. If successful, the number of additional bytes
- available is returned. If there is an error, -1 is returned.
+ available is returned. If there is an error, <literal>-1</literal> is returned.
Function: comedi_set_buffer_size -- streaming buffer size of subdevice
Retval: int
Param: unsigned int subdevice
Param: unsigned int size
Description:
- The function comedi_set_buffer_size() changes the size of the
- streaming buffer for the subdevice specified by device and subdevice.
- The parameter size must be a multiple of the virtual memory page
- size.
+ The function <function>comedi_set_buffer_size</function> changes the size of the
+ streaming buffer for the subdevice specified by
+ <parameter class="function">device</parameter> and <parameter
+ class="function">subdevice</parameter>.
+ The buffer size will be set to <parameter class="function">size</parameter> bytes,
+ rounded up to a multiple of the virtual memory page
+ size. The virtual memory page size can be determined using
+ <code language="C">sysconf(_SC_PAGE_SIZE)</code>.
- The virtual memory page size can be determined using
- sysconf(_SC_PAGE_SIZE).
+ This function does not require special privileges. However,
+ it is limited to a (adjustable) maximum buffer size, which can
+ be changed by a privileged user calling
+ <function><link
+ linkend="func-ref-comedi-set-max-buffer-size">comedi_set_max_buffer_size</link></function>,
+ or running the program <command>comedi_config</command>.
+Returns:
+ The new buffer size in bytes is returned on success. On error,
+ <literal>-1</literal> is returned.
-Function: comedi_set_max_buffer_size -- streaming buffer size of subdevice
+Function: comedi_set_max_buffer_size -- streaming maximum buffer size of subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int max_size
Description:
- The function comedi_set_max_buffer_size() changes the maximum
+ The function <function>comedi_set_max_buffer_size</function> changes the maximum
allowable size (in bytes) of the streaming buffer for the subdevice
- specified by device and subdevice. Changing the maximum buffer
- size requires appropriate privileges. If successful, the old buffer
- size is returned. On error, -1 is returned.
+ specified by <parameter class="function">device</parameter> and
+ <parameter class="function">subdevice</parameter>. Changing the maximum buffer
+ size requires the user to have appropriate privileges.
+Returns:
+ The new maximum buffer size is returned on success. On error, <literal>-1</literal> is returned.
projects / comedilib.git / blobdiff