comedi_mark_buffer_read man page

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 descriptor), 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

On success, comedi_mark_buffer_read returns the number of bytes successfully marked as read. The return value may be less than the num_bytes. On failure, -1 is returned.

Authors

David Schleef <ds@schleef.org>

Author.

Frank Mori Hess <fmhess@users.sourceforge.net>

Author.

Herman Bruyninckx <Herman.Bruyninckx@mech.kuleuven.ac.be>

Author.

Bernd Porr <tech@linux-usb-daq.co.uk>

Author.

Ian Abbott <abbotti@mev.co.uk>

Author.

Éric Piel <piel@delmic.com>

Author.

Info

05/11/2017 Comedi reference