focal (9) devfs_clear_cdevpriv.9freebsd.gz

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.