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.\" $FreeBSD: head/share/man/man9/devfs_set_cdevpriv.9 291653 2015-12-02 18:27:30Z jhb $
.\"
.Dd May 25, 2021
.Dt DEVFS_SET_CDEVPRIV 9
.Os
.Sh NAME
.Nm devfs_set_cdevpriv ,
.Nm devfs_get_cdevpriv ,
.Nm devfs_clear_cdevpriv
.Nd manage per-open filedescriptor data for devices
.Sh SYNOPSIS
.In sys/devfs.h
.Bd -literal
typedef	void d_priv_dtor_t(void *data);
.Ed
.Ft int
.Fn devfs_set_cdevpriv "struct file *fp" "void *priv" "d_priv_dtor_t *dtr"
.Ft int
.Fn devfs_get_cdevpriv "struct file *fp" "void **datap"
.Ft void
.Fn devfs_clear_cdevpriv "struct file *fp"
.Sh DESCRIPTION
The
.Fn devfs_xxx_cdevpriv
family of functions allows the device driver methods to associate some
driver-specific data with each user process
.Xr open 2
of the device special file.
Currently, functioning of these functions is restricted to the context
of the
.Vt dev_ops
switch method calls performed as
.Xr devfs 5
operations in response to system calls that use file descriptors.
.Pp
The
.Fn devfs_set_cdevpriv
function associates a data pointed by
.Fa priv
with the calling context (file descriptor) specified by
.Fa fp .
The data may be retrieved later by
.Fn devfs_get_cdevpriv ,
possibly from another call
performed on this file descriptor.
.Pp
The
.Fn devfs_clear_cdevpriv
function disassociates the previously attached data from the
context specified by
.Fa fp .
At the end of
.Fn devfs_clear_cdevpriv
operation, the previously associated
.Fa dtr
callback is called, with private data supplied its
.Fa data
argument.
The
.Fn devfs_clear_cdevpriv
function will be automatically called upon the
.Xr close 2
of the file descriptor.
.Sh RETURN VALUES
If successful, the functions return 0.
.Pp
The function
.Fn devfs_set_cdevpriv
returns the following values on error:
.Bl -tag -width Er
.It Bq Er ENOENT
The passed
.Fa fp
argument is
.Va NULL .
.It Bq Er EBUSY
The private driver data is already associated with the given
.Fa fp .
.El
.Pp
The function
.Fn devfs_get_cdevpriv
returns the following values on error:
.Bl -tag -width Er
.It Bq Er EBADF
The passed
.Fa fp
argument is
.Va NULL .
.It Bq Er ENOENT
The private driver data was not associated with the given
.Fa fp ,
or
.Fn devfs_clear_cdevpriv
was called.
.El
.Sh SEE ALSO
.Xr close 2 ,
.Xr open 2 ,
.Xr devfs 5
.Sh HISTORY
The
.Fn devfs_xxx_cdevpriv
family of functions first appeared in
.Fx 7.1 ,
and was implemented in
.Dx 3.8 .