Name

comedi_mark_buffer_written — streaming buffer control

Synopsis

#include <comedilib.h>
int comedi_mark_buffer_written(comedi_t * device,
 unsigned int subdevice,
 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 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.

Return value

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)).