Specifications

Comedi
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Synopsis
#include <comedilib.h>
int comedi_get_read_subdevice(comedi_t * device);
Description
The function comedi_get_read_subdevice() returns the index of the subdevice whose streaming input buffer is accessible
through the device device. If there is no such subdevice, -1 is returned.
5.4.2.11 comedi_get_write_subdevice
comedi_get_write_subdevice — find streaming output subdevice
Synopsis
#include <comedilib.h>
int comedi_get_write_subdevice(comedi_t * device);
Description
The function comedi_get_write_subdevice() returns the index of the subdevice whose streaming output buffer is acces-
sible through the device device. If there is no such subdevice, -1 is returned.
5.4.2.12 comedi_mark_buffer_read
comedi_mark_buffer_read — streaming buffer control
Synopsis
#include <comedilib.h>
int comedi_mark_buffer_read(comedi_t * device, unsigned int subdevice, 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() mapping to read data from Comedi’s buffer (as opposed to calling read() 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 are no longer needed and may be discarded.
Return value
The function comedi_mark_buffer_read() returns the number of bytes successfully marked as read, or -1 on error. The
return value may be less than num_bytes if you attempt to mark more bytes read than are currently available for reading, or
if num_bytes must be rounded down to be an exact multiple of the subdevice’s sample size (either sizeof(sampl_t) or
sizeof(lsampl_t)).
5.4.2.13 comedi_mark_buffer_written
comedi_mark_buffer_written — streaming buffer control