ioctl_pipe(2)                 System Calls Manual                ioctl_pipe(2)

NAME
       ioctl_pipe - ioctl() operations for General notification mechanism

SYNOPSIS
       #include <linux/watch_queue.h>  /* Definition of IOC_WATCH_QUEUE_* */
       #include <sys/ioctl.h>

       int ioctl(int pipefd[1], IOC_WATCH_QUEUE_SET_SIZE, int size);
       int ioctl(int pipefd[1], IOC_WATCH_QUEUE_SET_FILTER,
                 struct watch_notification_filter *filter);

DESCRIPTION
       The following ioctl(2) operations are provided to set up general
       notification queue parameters.  The notification queue is built on the
       top of a pipe(2) opened with the O_NOTIFICATION_PIPE flag.

       IOC_WATCH_QUEUE_SET_SIZE (since Linux 5.8)
              Preallocates the pipe buffer memory so that it can fit size
              notification messages.  Currently, size must be between 1 and
              512.

       IOC_WATCH_QUEUE_SET_FILTER (since Linux 5.8)
              Watch queue filter can limit events that are received.  Filters
              are passed in a struct watch_notification_filter and each filter
              is described by a struct watch_notification_type_filter
              structure.

                  struct watch_notification_filter {
                          __u32   nr_filters;
                          __u32   __reserved;
                          struct watch_notification_type_filter filters[];
                  };

                  struct watch_notification_type_filter {
                          __u32   type;
                          __u32   info_filter;
                          __u32   info_mask;
                          __u32   subtype_filter[8];
                  };

SEE ALSO
       pipe(2), ioctl(2)

Linux man-pages 6.8               2024-05-02                     ioctl_pipe(2)