NAME

       devfs_set_cdevpriv,  devfs_get_cdevpriv,  devfs_clear_cdevpriv  — manage per-open filedescriptor data for
       devices

SYNOPSIS

       #include <sys/param.h>
       #include <sys/conf.h>

       typedef void d_priv_dtor_t(void *data);

       int
       devfs_get_cdevpriv(void **datap);

       int
       devfs_set_cdevpriv(void *priv, d_priv_dtor_t *dtr);

       void
       devfs_clear_cdevpriv(void);

DESCRIPTION

       The devfs_xxx_cdevpriv() family of functions allows the cdev driver methods  to  associate  some  driver-
       specific data with each user process open(2) of the device special file.  Currently, functioning of these
       functions is restricted to the context of the cdevsw switch method calls performed as devfs(5) operations
       in response to system calls that use filedescriptors.

       The  devfs_set_cdevpriv()  function  associates  a  data  pointed  by  priv  with current calling context
       (filedescriptor).  The data may be  retrieved  later,  possibly  from  another  call  performed  on  this
       filedescriptor,   by   the   devfs_get_cdevpriv()  function.   The  devfs_clear_cdevpriv()  disassociates
       previously attached data from context.  Immediately after devfs_clear_cdevpriv() finished operating,  the
       dtr  callback  is  called, with private data supplied data argument.  The devfs_clear_cdevpriv() function
       will be also be called if the open callback function returns an error code.

       On the last filedescriptor close, system automatically arranges devfs_clear_cdevpriv() call.

       If successful, the functions return 0.

       The function devfs_set_cdevpriv() returns the following values on error:

       [ENOENT]           The current call is not associated with some filedescriptor.

       [EBUSY]            The private driver data is already associated with current filedescriptor.

       The function devfs_get_cdevpriv() returns the following values on error:

       [EBADF]            The current call is not associated with some filedescriptor.

       [ENOENT]           The  private  driver  data  was  not  associated  with  current   filedescriptor,   or
                          devfs_clear_cdevpriv() was called.

SEE ALSO

       close(2), open(2), devfs(5)

HISTORY

       The devfs_cdevpriv() family of functions first appeared in FreeBSD 7.1.

Debian                                          December 2, 2015                               DEVFS_CDEVPRIV(9)