comedi_get_buffer_contents — streaming buffer status
#include <comedilib.h>
| int comedi_get_buffer_contents( | comedi_t * device, | 
| unsigned int subdevice ); | 
The function comedi_get_buffer_contents is used on a subdevice
that has a Comedi command in progress to get the number of unread bytes.  For
a streaming input command, this is the number of bytes that can be read.  For
a streaming output command, subtracting this from the buffer size gives the
space available to be written.