comedi_do_insnlist man page
comedi_do_insnlist — perform multiple instructions
int comedi_do_insnlist (comedi_t * device, comedi_insnlist * list);
The function comedi_do_insnlist() performs multiple Comedi instructions as part of one system call. In addition, Comedi attempts to perform the instructions atomically, that is, on standard Linux kernels, no process preemption should occur during the instructions. However, the process may be preempted before or after the group of instructions.
This function can be used to avoid the overhead of multiple system calls, or to ensure that multiple instructions occur without significant delay between them.
Preemption may occur if any of the instructions or the data arrays of any of the instructions exist in non-resident or copy-on-write pages.
The function comedi_do_insnlist() returns the number of sucessfully completed instructions. Error information for the unsucessful instruction is not available. If there is an error before the first instruction can be executed, -1 is returned.