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 Comedi command
 previously started by comedi_command() that is still in progress
 on the subdevice indicated by the parameters device and subdevice.
 This may not return the subdevice to a ready state, since there may
 be samples in the buffer that need to be read.

 If successful, 0 is returned, otherwise -1.

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.
 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: 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
 testing stages that were successfully passed.  In addition, if elements
 of the command 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.

 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.

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
 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.

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
 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.

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.

Function: comedi_get_cmd_generic_timed -- streaming input/output capabilities
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: comedi_cmd * command
Param: unsigned int chanlist_len
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.

Function: comedi_get_cmd_src_mask -- streaming input/output capabilities
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
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.

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
 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.

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".

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".

Function: comedi_mark_buffer_read -- streaming buffer control
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int num_bytes
Description:
 The function comedi_mark_buffer_read() 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,
 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
 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.

Function: comedi_mark_buffer_written -- streaming buffer control
Retval: int
Param: comedi_t * device
Param: unsigned int subdevice
Param: unsigned int num_bytes
Description:
 The function comedi_mark_buffer_written() 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
 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
 are valid and may be sent to the device.
 If there is an error, -1 is returned.

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
 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.

Function: comedi_set_buffer_size -- streaming buffer size of subdevice
Retval: int
Param: comedi_t * device
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 virtual memory page size can be determined using
 sysconf(_SC_PAGE_SIZE).

Function: comedi_set_max_buffer_size -- streaming 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
 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.