devfs_set_cdevpriv (9)

Leading comments

Copyright (c) 2008 Konstantin Belousov
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(The comments found at the beginning of the groff file "man9/devfs_set_cdevpriv.9freebsd".)

NAME

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

SYNOPSIS

In sys/param.h In sys/conf.h

typedef void (*cdevpriv_dtr_t)(void *data);

Ft int Fn devfs_get_cdevpriv void **datap Ft int Fn devfs_set_cdevpriv void *priv cdevpriv_dtr_t dtr Ft void Fn devfs_clear_cdevpriv void

DESCRIPTION

The Fn devfs_xxx_cdevpriv family of functions allows the Fa 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 Fa cdevsw switch method calls performed as devfs(5) operations in response to system calls that use filedescriptors.

The Fn 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 Fn devfs_get_cdevpriv function. The Fn devfs_clear_cdevpriv disassociates previously attached data from context. Immediately after Fn devfs_clear_cdevpriv finished operating, the dtr callback is called, with private data supplied data argument. The Fn 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 Fn devfs_clear_cdevpriv call.

If successful, the functions return 0.

The function Fn devfs_set_cdevpriv returns the following values on error:

Bq Er ENOENT

The current call is not associated with some filedescriptor.

Bq Er EBUSY

The private driver data is already associated with current filedescriptor.

The function Fn devfs_get_cdevpriv returns the following values on error:

Bq Er EBADF

The current call is not associated with some filedescriptor.

Bq Er ENOENT

The private driver data was not associated with current filedescriptor, or Fn devfs_clear_cdevpriv was called.

SEE ALSO

open(2), close(2), devfs(5), kern_openat9

HISTORY

The Fn devfs_cdevpriv family of functions first appeared in Fx 7.1 .