Manual Pages for UNIX Operating System command usage for man chpoll

Driver Entry Points                                    chpoll(9E)



NAME
     chpoll - poll entry point for a non-STREAMS character driver

SYNOPSIS
     #include 
     #include 
     #include 
     #include 



     int prefixchpoll(dev_t dev, short events, int anyyet,
          short *reventsp, struct pollhead **phpp);


INTERFACE LEVEL
     This entry point is optional. Architecture independent level
     1 (DDI/DKI).

PARAMETERS
     dev         The device number for the device to be polled.


     events      The events that may occur. Valid events are:

                 POLLIN        Data other than high priority data
                               may be read without blocking.


                 POLLOUT       Normal data may be written without
                               blocking.


                 POLLPRI       High priority data may be received
                               without blocking.


                 POLLHUP       A device hangup has occurred.


                 POLLERR       An error has occurred on the  dev-
                               ice.


                 POLLRDNORM    Normal data (priority  band  =  0)
                               may be read without blocking.


                 POLLRDBAND    Data from a non-zero priority band
                               may be read without blocking





SunOS 5.11           Last change: 7 May 2008                    1






Driver Entry Points                                    chpoll(9E)



                 POLLWRNORM    The same as POLLOUT.


                 POLLWRBAND    Priority data (priority band >  0)
                               may be written.



     anyyet      A flag  that  is  non-zero  if  any  other  file
                 descriptors  in  the  pollfd  array  have events
                 pending. The poll(2) system call takes a pointer
                 to  an  array of pollfd structures as one of its
                 arguments. See the poll(2)  reference  page  for
                 more details.


     reventsp    A pointer to a bitmask of  the  returned  events
                 satisfied.


     phpp        A pointer to a pointer to a pollhead structure.


DESCRIPTION
     The chpoll() entry point  routine  is  used  by  non-STREAMS
     character  device  drivers that wish to support polling. The
     driver must implement the  polling  discipline  itself.  The
     following  rules must be followed when implementing the pol-
     ling discipline:

         1.   Implement the following algorithm when the chpoll()
              entry point is called:

                if (events_are_satisfied_now) {
                      *reventsp = satisfied_events & events;
                } else {
                      *reventsp = 0;
                      if (!anyyet)
                            *phpp = &my_local_pollhead_structure;
                }
                return (0);


         2.   Allocate an instance  of  the  pollhead  structure.
              This  instance  may  be  tied to the per-minor data
              structure  defined  by  the  driver.  The  pollhead
              structure should be treated as a "black box" by the
              driver. Initialize the pollhead structure  by  fil-
              ling  it with zeroes. The size of this structure is
              guaranteed to remain the same across releases.

         3.   Call the pollwakeup() function with  events  listed



SunOS 5.11           Last change: 7 May 2008                    2






Driver Entry Points                                    chpoll(9E)



              above  whenever  pollable  events  which the driver
              should monitor occur. This function can  be  called
              with  multiple  events at one time. The pollwakup()
              can be called regardless  of  whether  or  not  the
              chpoll() entry is called; it should be called every
              time the driver detects  the  pollable  event.  The
              driver  must  not hold any mutex across the call to
              pollwakeup(9F) that is  acquired  in  its  chpoll()
              entry point, or a deadlock may result.

RETURN VALUES
     chpoll() should return 0 for  success,  or  the  appropriate
     error number.

SEE ALSO
     poll(2), nochpoll(9F), pollwakeup(9F)


     Writing Device Drivers




































SunOS 5.11           Last change: 7 May 2008                    3