comedi_mark_buffer_written(3) streaming buffer control


#include <comedilib.h>

int comedi_mark_buffer_written(comedi_t * device, unsigned int subdevice, unsigned int num_bytes);


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 mapping to write data to Comedi's buffer (as opposed to calling write on the device file), 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.


The function comedi_mark_buffer_written returns number of bytes successfully marked as written, or -1 on error. The return value may be less than num_bytes if you attempt to mark more bytes written than the amount of free space currently available in the output buffer, 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)).


David Schleef <[email protected]>


Frank Mori Hess <[email protected]>


Herman Bruyninckx <[email protected]>


Bernd Porr <[email protected]>


Ian Abbott <[email protected]>


Éric Piel <[email protected]>



Copyright © 1998-2003 David Schleef
Copyright © 2001-2003, 2005, 2008 Frank Mori Hess
Copyright © 2002-2003 Herman Bruyninckx
Copyright © 2012 Bernd Porr
Copyright © 2012 Ian Abbott
Copyright © 2012 Éric Piel

This document is part of Comedilib. In the context of this document, the term "source code" as defined by the license is interpreted as the XML source.

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, version 2.1 of the License.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.