Extensions
Function: comedi_arm -- arm a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int source
Status: alpha
Description:
 This function arms a subdevice.  It may, for example, arm a counter to
 begin counting.  The <parameter class="function">source</parameter>
 parameter specifies what source should trigger the subdevice to begin.
 The possible sources are driver-dependant.  This function is only
 useable on subdevices that provide support for the
 <constant>INSN_CONFIG_ARM</constant> configuration instruction.
 Some subdevices treat this as an instruction to arm a specific channel.
 For those subdevices, this function will arm channel
 <literal>0</literal> and <function><link
 linkend="func-ref-comedi-arm-channel">comedi_arm_channel</link></function>
 should be called instead of this one to specify the channel.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_arm_channel -- arm a subdevice channel
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int source
Status: alpha
Description:
 This function arms a specified channel of a subdevice.  It may, for
 example, arm a counter to begin counting.  The <parameter
 class="function">source</parameter> parameter specifies what source
 should trigger the subdevice to begin.  The possible sources are
 driver-dependant.  This function is only useable on subdevices that
 provide support for the <constant>INSN_CONFIG_ARM</constant>
 configuration instruction.  Some subdevices treat this as an
 instruction to arm the whole subdevice and ignore the specified
 channel.  For such subdevices, <function><link
 linkend="func-ref-comedi-arm">comedi_arm</link></function> is normally
 called instead.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_connect_route -- connect device-global route
Retval: int
Param: comedi_t * device
Param: unsigned int source
Param: unsigned int destination
Status: alpha
Description:
 This function connects a globally-named route if such is connectible.
 
 This operation is effectively the same as calling <function><link
 linkend="func-ref-comedi-set-routing">comedi_set_routing</link></function> and
 <function><link
 linkend="func-ref-comedi-dio-config">comedi_dio_config</link></function> on the
 appropriate subdevice.
 
 There are several routes that are not globally connectable via <function><link
 linkend="func-ref-comedi-connect-route">comedi_connect_route</link></function>,
 such as (<code language="C">NI_PFI(i)</code> -->
 <constant>NI_AO_SampleClock</constant>) as they must be connected via a trigger
 argument, such as <code language="C">comedi_cmd->start_arg</code> for
 <constant>NI_AO_StartTrigger</constant>.

 The <parameter class="function">source</parameter> parameter specifies the
 source of the signal route, whereas the <parameter
 class="function">destination</parameter> parameter specifies the destination.
 Possible values for source and destination are driver dependent but are
 generally required to be values that are recognizable globally for a particular
 device, independent of sub-device.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error (and errno is
 set appropriately--EALREADY: route is already connected; EINVAL: route invalid
 for this device; EBUSY: destination selector used for another route).

Function: comedi_digital_trigger_disable -- disable a digital trigger
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int trigger_id
Status: alpha
Description:
 This function disables a digital trigger on a subdevice, returning it
 to its default, inactive, unconfigured state.  If the subdevice
 supports several digital triggers, the <code language="C"><parameter
 class="function">trigger_id</parameter></code> selects one.

 This function is only useable on subdevices that provide support for
 the <constant>INSN_CONFIG_DIGITAL_TRIG</constant> configuration
 instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_digital_trigger_enable_edges -- set digital trigger edge detection
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int trigger_id
Param: unsigned int base_input
Param: unsigned int rising_edge_inputs
Param: unsigned int falling_edge_inputs
Status: alpha
Description:
 This function enables edge detection for a digital trigger on a
 subdevice.  If the subdevice supports several digital triggers, the
 <code language="C"><parameter
 class="function">trigger_id</parameter></code> selects one.  The <code
 language="C"><parameter
 class="function">rising_edge_inputs</parameter></code> and <code
 language="C"><parameter
 class="function">falling_edge_inputs</parameter></code> parameters are
 bit fields that enable (1) or disable (0) rising and falling edge
 detection on a set of (up to) 32 inputs.  The least-significant bit
 corresponds to the input specified by the <code
 language="C"><parameter>base_input</parameter></code> parameter, with
 subsequent bits corresponding to subsequent inputs.

 Successive calls to this function have an cumulative effect, which
 allows digital triggers to be set up for more than 32 inputs.  There
 may also be a cumulative effect with calls to <function><link
 linkend="func-ref-comedi-digital-trigger-enable-levels">comedi_digital_trigger_enable_levels</link></function>
 if the digital trigger supports a combination of edge and level
 triggering.  Due to the cumulative effect, it may be necessary to call
 <function><link
 linkend="func-ref-comedi-digital-trigger-disable">comedi_digital_trigger_disable</link></function>
 to clear the old settings before reconfiguring the digital trigger
 inputs.

 A digital trigger may support edge detection, level detection, both at
 different times, or both at the same time.  If it supports both but not
 at the same time, configuring edge triggers will disable any previous
 level triggers, or vice versa.

 This function is only useable on subdevices that provide support for
 the <constant>INSN_CONFIG_DIGITAL_TRIG</constant> configuration
 instruction, and only if the digital trigger supports edge detection.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_digital_trigger_enable_levels -- set digital trigger level detection
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int trigger_id
Param: unsigned int base_input
Param: unsigned int high_level_inputs
Param: unsigned int low_level_inputs
Status: alpha
Description:
 This function enables level detection for a digital trigger on a
 subdevice.  If the subdevice supports several digital triggers, the
 <code language="C"><parameter
 class="function">trigger_id</parameter></code> selects one.  The <code
 language="C"><parameter
 class="function">high_level_inputs</parameter></code> and <code
 language="C"><parameter
 class="function">low_level_inputs</parameter></code> parameters are
 bit fields that enable (1) or disable (0) high and low level
 detection on a set of (up to) 32 inputs.  The least-significant bit
 corresponds to the input specified by the <code
 language="C"><parameter>base_input</parameter></code> parameter, with
 subsequent bits corresponding to subsequent inputs.

 Successive calls to this function have an cumulative effect, which
 allows digital triggers to be set up for more than 32 inputs.  There
 may also be a cumulative effect with calls to <function><link
 linkend="func-ref-comedi-digital-trigger-enable-edges">comedi_digital_trigger_enable_edges</link></function>
 if the digital trigger supports a combination of edge and level
 triggering.  Due to the cumulative effect, it may be necessary to call
 <function><link
 linkend="func-ref-comedi-digital-trigger-disable">comedi_digital_trigger_disable</link></function>
 to clear the old settings before reconfiguring the digital trigger
 inputs.

 A digital trigger may support edge detection, level detection, both at
 different times, or both at the same time.  If it supports both but not
 at the same time, configuring level triggers will disable any previous
 edge triggers, or vice versa.

 This function is only useable on subdevices that provide support for
 the <constant>INSN_CONFIG_DIGITAL_TRIG</constant> configuration
 instruction, and only if the digital trigger supports level detection.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_disarm -- disarm a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Status: alpha
Description:
 This function disarms a subdevice.  It may, for example, stop a counter
 counting.  This function is only useable on subdevices that provide
 support for the <constant>INSN_CONFIG_DISARM</constant> configuration
 instruction.  Some subdevices treat this as an instruction to disarm a
 specific channel.  For those subdevices, this function will disarm
 channel <literal>0</literal> and <function><link
 linkend="func-ref-comedi-disarm-channel">comedi_disarm_channel</link></function>
 should be called instead of this one to specify the channel.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_disarm_channel -- disarm a subdevice channel
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Status: alpha
Description:
 This function disarms a specified channel of a subdevice.  It may, for
 example, stop a counter counting.  This function is only useable on
 subdevices that provide support for the
 <constant>INSN_CONFIG_DISARM</constant> configuration instruction.
 Some subdevices treat this as an instruction to disarm the whole
 subdevice and ignore the specified channel.  For such subdevices,
 <function><link
 linkend="func-ref-comedi-disarm">comedi_disarm</link></function> is
 normally called instead.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_disconnect_route -- disconnect device-global route
Retval: int
Param: comedi_t * device
Param: unsigned int source
Param: unsigned int destination
Status: alpha
Description:
 This function disconnects a globally-named route if such is connected.
 
 This operation is effectively the same as calling <function><link
 linkend="func-ref-comedi-set-routing">comedi_set_routing</link></function> and
 <function><link
 linkend="func-ref-comedi-dio-config">comedi_dio_config</link></function> on the
 appropriate subdevice.
 
 There are several routes that are not globally dis-connectable via
 <function><link
 linkend="func-ref-comedi-connect-route">comedi_connect_route</link></function>,
 such as (<code language="C">NI_PFI(i)</code> -->
 <constant>NI_AO_SampleClock</constant>) as they must be connected via a trigger
 argument, such as <code language="C">comedi_cmd->start_arg</code> for
 <constant>NI_AO_StartTrigger</constant>.

 The <parameter class="function">source</parameter> parameter specifies the
 source of the signal route, whereas the <parameter
 class="function">destination</parameter> parameter specifies the destination.
 Possible values for source and destination are driver dependent but are
 generally required to be values that are recognizable globally for a particular
 device, independent of sub-device.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_get_clock_source -- get master clock for a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int * clock
Param: unsigned int * period_ns
Status: alpha
Description:
 This function queries the master clock for a subdevice, as
 set by
 <function><link linkend="func-ref-comedi-set-clock-source">comedi_set_clock_source</link></function>.
 The currently configured master clock
 will be written to
 <code language="C">*<parameter class="function">clock</parameter></code>.
 The possible values and their corresponding clocks are
 driver-dependant.
 The period of the clock in nanoseconds (or zero if it is unknown)
 will be written to
 <code language="C">*<parameter class="function">period_ns</parameter></code>.
 If the subdevice does not support configuring its master clocks
 on a per-channel basis, then the <parameter class="function">channel</parameter>
 parameter will be ignored.

 It is safe to pass <constant>NULL</constant> pointers as the
 <parameter class="function">clock</parameter> or
 <parameter class="function">period_ns</parameter>
 parameters.  This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_GET_CLOCK_SRC</constant>
 configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_get_cmd_timing_constraints -- Get the hardware timing constraints for a streaming subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int scan_begin_src
Param: unsigned int * scan_begin_min
Param: unsigned int convert_src
Param: unsigned int * convert_min
Param: unsigned int * chanlist
Param: unsigned int chanlist_len
Status: alpha
Description:
 This function queries the hardware timing constraints of a streaming subdevice.

 The values returned by this function may indicate the range of valid inputs
 for
 <code language="C">comedi_cmd->scan_begin_arg</code> and
 <code language="C">comedi_cmd->convert_arg</code>, for instance when
 <code language="C">comedi_cmd->scan_begin_src==TRIG_TIMER</code> or
 <code language="C">comedi_cmd->convert_src==TRIG_TIMER</code>.  For
 <code language="C">TRIG_EXT</code> (or other modes?), these returned values are
 mostly informational and may be used in conjunction with other triggering
 hardware.

 If it is possible for the hardware constraints to depend on whether
 <code language="C">[*]_src==TRIG_TIMER</code> or
 <code language="C">[*]_src==TRIG_EXT</code>, the values returned by this
 function will depend on these inputs.  Alternatively, one can specify something
 like <code language="C">[*]_src==TRIG_TIMER|TRIG_EXT</code> and retrieve the
 value that is the smallest that satisfies both trigger sources.

 <parameter class="function">scan_begin_min</parameter> may be given as
 <code language="C">NULL</code>, such that nothing will be returned for minimum
 scan speed.

 <parameter class="function">convert_min</parameter> may be given as
 <code language="C">NULL</code>, such that nothing will be returned for minimum
 scan speed.

Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_get_gate_source -- get gate for a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int gate_index
Param: unsigned int * gate_source
Status: alpha
Description:
 This function queries the gate for a subdevice, as set by
 <function><link linkend="func-ref-comedi-set-gate-source">comedi_set_gate_source</link></function>.
 The currently configured gate source
 will be written to
 <code language="C">*<parameter class="function">gate_source</parameter></code>.
 The possible values and their corresponding gates are
 driver-dependant.  If the subdevice does not
 support configuring its gates on a per-channel basis, then the
 <parameter class="function">channel</parameter> parameter will be ignored.

 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_GET_GATE_SRC</constant>
 configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_get_hardware_buffer_size -- get size of subdevice's hardware buffer
Retval: int
Param: comedi_t *device
Param: unsigned int subdevice
Param: <link linkend="ref-enum-comedi-io-direction">enum comedi_io_direction</link> direction
Description:
 This function returns the number of bytes the subdevice can hold in it's hardware buffer.
 The term <quote>hardware buffer</quote> refers to any FIFOs, etc. on the acquisition board itself which
 are used during streaming commands.  This does not include the buffer maintained by
 the comedi kernel module in host memory, whose size may be queried by
 <function><link
 linkend="func-ref-comedi-get-buffer-size">comedi_get_buffer_size</link></function>.
 The <parameter class="function">direction</parameter> parameter of type
 <type><link linkend="ref-enum-comedi-io-direction">enum
 comedi_io_direction</link></type>
 should be set to <constant>COMEDI_INPUT</constant> to query the input buffer size (e.g., the buffer of an analog
 input subdevice), or <constant>COMEDI_OUTPUT</constant> to query the output buffer size (e.g., the buffer of
 an analog output).
Returns:
 Hardware buffer size in bytes, or <literal>-1</literal> on error.

Function: comedi_get_routes -- obtain list of all possible device-globally named routes
Retval: int
Param: comedi_t * device
Param: comedi_route_pair * routelist
Param: size_t n
Status: alpha
Description:
 This function obtains a list of all possible globally-named routes for the
 particular device.

 A globally-named route is a route where the source and destination values are
 globally recognized, regardless of the subdevice.
 
 This function returns all possible signal routes that are either connectible
 via <code language="C">comedi_cmd->start_arg</code> aruments or via the
 device-global configuration interface of <function><link
 linkend="func-ref-comedi-connect-route">comedi_connect_route</link></function>
 and <function><link
 linkend="func-ref-comedi-connect-route">comedi_disconnect_route</link></function>.

 The <parameter class="function">routelist</parameter> parameter provides memory
 into which the results may be copied.  The <code language="C">comedi_route_pair</code> is
 (as specified in <emphasis>comedi.h</emphasis>):
 <programlisting>
    typedef struct {
      unsigned int source;
      unsigned int destination;
    } comedi_route_pair;
 </programlisting>

 <parameter class="function">routelist</parameter> may be specified as
 <constant>NULL</constant>, in which case only the number of routes will be
 returned.

 The <parameter class="function">n</parameter> parameter provides specifies the
 number of slots available in the <parameter
 class="function">routelist</parameter> array.
Returns:
 The number of routes available if <parameter
 class="function">routelist</parameter> is <constant>NULL</constant>, the number
 of routes copied if <parameter class="function">routelist</parameter> is not
 <constant>NULL</constant>, or <literal>-1</literal> on error.

Function: comedi_get_routing -- get routing for an output
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int * routing
Status: alpha
Description:
 This function queries the routing for an output, as
 set by
 <function><link linkend="func-ref-comedi-set-routing">comedi_set_routing</link></function>.
 The currently configured routing
 will be written to
 <code language="C">*<parameter class="function">routing</parameter></code>.
 The possible values and their corresponding routings are
 driver-dependant.

 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_GET_ROUTING</constant>
 configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_reset -- reset a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Status: alpha
Description:
 This function resets a subdevice.  It is only useable on subdevices
 that provide support for the <constant>INSN_CONFIG_RESET</constant>
 configuration instruction.  Some subdevices treat this as an
 instruction to reset a specific channel.  For those subdevices, this
 function will reset channel <literal>0</literal> and <function><link
 linkend="func-ref-comedi-reset-channel">comedi_reset_channel</link></function>
 should be called instead of this one to specify the channel.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_reset_channel -- reset a subdevice channel
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Status: alpha
Description:
 This function resets a specified channel of a subdevice.  It is only
 useable on subdevices that provide support for the
 <constant>INSN_CONFIG_RESET</constant> configuration instruction.  Some
 subdevices treat this as an instruction to reset the whole subdevice
 and ignore the specified channel.  For such subdevices, <function><link
 linkend="func-ref-comedi-reset">comedi_reset</link></function> is
 normally called instead.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_set_clock_source -- set master clock for a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int clock
Param: unsigned int period_ns
Status: alpha
Description:
 This function selects a master clock for a subdevice.  The <parameter
 class="function">clock</parameter>
 parameter selects the master clock, and is driver-dependant.  
 If the subdevice does not support configuring its master clocks on a
 per-channel basis, then the <parameter class="function">channel</parameter> parameter
 will be ignored.
 The <parameter class="function">period_ns</parameter>
 parameter specifies the clock's period in nanoseconds.  It may left unspecified by using
 a value of zero.  Drivers will ignore the clock period if they already
 know what the clock period should be for the specified clock (e.g. for an
 on-board 20MHz oscillator).  Certain boards which use a phase-locked loop to
 synchronize to external clock sources must be told the period of the external
 clock. Specifying a clock period for an external clock may also allow
 the driver to support <constant>TRIG_TIMER</constant> sources in commands while
 using the external clock.

 The clock may be queried with the
 <function><link linkend="func-ref-comedi-get-clock-source">comedi_get_clock_source</link></function>
 function.

 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_SET_CLOCK_SRC</constant> configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_set_counter_mode -- change mode of a counter subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int mode
Status: alpha
Description:
 This function configures a counter subdevice.  The meaning of the
 <parameter class="function">mode</parameter> parameter is driver-dependent.
 If the subdevice does not
 support configuring its mode on a per-channel basis, then the
 <parameter class="function">channel</parameter>
 parameter will be ignored.

 It is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_SET_COUNTER_MODE</constant> configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_set_filter -- select a filter for a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int filter
Status: alpha
Description:
 This function selects a filter for a subdevice.  For instance, a digital
 input subdevice may provide deglitching filters with varying cutoff frequencies.
 The filters are used to prevent high-frequency
 noise from causing unwanted transitions on the digital inputs.  This function can
 tell the hardware which deglitching filter to use, or to use none at all.

 The <parameter class="function">filter</parameter>
 parameter selects which of the subdevice's filters to use, and is driver-dependant.

 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_FILTER</constant> configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_set_gate_source -- select gate source for a subdevice
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int gate_index
Param: unsigned int gate_source
Status: alpha
Description:
 This function selects a gate source for a subdevice.  The
 <parameter class="function">gate_index</parameter>
 parameter selects which gate is being configured, should the subdevice have
 multiple gates.  It takes a value
 from 0 to N-1 for a subdevice with N different gates.
 The <parameter class="function">gate_source</parameter> parameter selects which signal you wish to
 use as
 the gate, and is also driver-dependent.  If the subdevice does not
 support configuring its gates on a per-channel basis, then the
 <parameter class="function">channel</parameter> parameter will be ignored.

 You may query the gate source with the
 <function><link linkend="func-ref-comedi-get-gate-source">comedi_get_gate_source</link></function>
 function.
 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_SET_GATE_SRC</constant>
 configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_set_other_source -- select source signal for something other than a gate or clock
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int other
Param: unsigned int source
Status: alpha
Description:
 This function allows selection of a source signal for something on a subdevice
 other than a gate (which uses
 <function><link
 linkend="func-ref-comedi-set-gate-source">comedi_set_gate_source</link></function>)
 or a clock (which uses
 <function><link
 linkend="func-ref-comedi-set-clock-source">comedi_set_clock_source</link></function>).
 The <parameter class="function">other</parameter> parameter selects
 which <quote>other</quote> we are configuring, and is driver-dependent.  The
 <parameter class="function">source</parameter> parameter selects the source
 we which to use for the <quote>other</quote>.  If the subdevice does not
 support configuring its <quote>other</quote> sources on a per-channel basis,
 then the <parameter class="function">channel</parameter>
 parameter will be ignored.

 As an example, this function is used to select which PFI digital input channels
 should be used as the A/B/Z signals when running a counter on an NI M-Series board as
 a quadrature encoder.  The <parameter class="function">other</parameter> parameter selects either the A, B,
 or Z signal, and the <parameter class="function">source</parameter> parameter is used to specify
 which PFI digital input channel the external A, B, or Z signal is
 physically connected to.

 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_SET_OTHER_SRC</constant>
 configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_set_routing -- select a routing for an output
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int channel
Param: unsigned int routing
Status: alpha
Description:
 This function configures a mutiplexed output channel which can
 output a variety of different signals (such as NI's RTSI and PFI lines).
 The <parameter class="function">routing</parameter>
 parameter selects which signal should be routed to appear on the
 selected output channel, and is driver-dependant.

 The routing may be queried with the
 <function><link linkend="func-ref-comedi-get-routing">comedi_get_routing</link></function>
 function.
 This function is only useable
 on subdevices that provide support for the
 <constant>INSN_CONFIG_SET_ROUTING</constant>
 configuration instruction.
Returns:
 <literal>0</literal> on success, <literal>-1</literal> on error.

Function: comedi_test_route -- validate and test device-global route
Retval: int
Param: comedi_t * device
Param: unsigned int source
Param: unsigned int destination
Status: alpha
Description:
 This function validates a globally-named route as connectible and tests whether
 the route is connected.
 
 Note that since <function><link
 linkend="func-ref-comedi-connect-route">comedi_connect_route</link></function>
 and <function><link
 linkend="func-ref-comedi-disconnect-route">comedi_disconnect_route</link></function>
 effectively perform the same operations as <function><link
 linkend="func-ref-comedi-set-routing">comedi_set_routing</link></function> /
 <function><link
 linkend="func-ref-comedi-get-routing">comedi_get_routing</link></function> and
 <function><link
 linkend="func-ref-comedi-dio-config">comedi_dio_config</link></function>, this
 operation will only report a route as connected _if_ both operations have been
 performed directly or effectively via comedi_connect_route.
 
 There are several routes that are not globally connectable via <function><link
 linkend="func-ref-comedi-connect-route">comedi_connect_route</link></function>,
 such as (<code language="C">NI_PFI(i)</code> -->
 <constant>NI_AO_SampleClock</constant>) as they must be connected via a trigger
 argument, such as <code language="C">comedi_cmd->start_arg</code> for
 <constant>NI_AO_StartTrigger</constant>.  This function can still be used for
 such routes to test whether they are valid.

 The <parameter class="function">source</parameter> parameter specifies the
 source of the signal route, whereas the <parameter
 class="function">destination</parameter> parameter specifies the destination.
 Possible values for source and destination are driver dependent but are
 generally required to be values that are recognizable globally for a particular
 device, independent of sub-device.
Returns:
 <literal>-1</literal> if not connectible, <literal>0</literal> if connectible
 but not connected, <literal>1</literal> if connectible <emphasis>and</emphasis>
 connected.