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like the various d_*_t typedefs since it declared a function pointer rather than a function. Add a new d_priv_dtor_t typedef that declares the function and can be used as a function prototype. The previous typedef wasn't useful outside of the cdevpriv implementation, so retire it. The name d_priv_dtor_t was chosen to be more consistent with cdev methods since it is commonly used in place of d_close_t even though it is not a direct pointer in struct cdevsw. Reviewed by: kib, imp MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D4340
125 lines
3.6 KiB
Groff
125 lines
3.6 KiB
Groff
.\" Copyright (c) 2008 Konstantin Belousov
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 2, 2015
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.Dt DEVFS_CDEVPRIV 9
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.Os
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.Sh NAME
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.Nm devfs_set_cdevpriv ,
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.Nm devfs_get_cdevpriv ,
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.Nm devfs_clear_cdevpriv
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.Nd manage per-open filedescriptor data for devices
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/conf.h
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.Bd -literal
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typedef void d_priv_dtor_t(void *data);
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.Ed
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.Ft int
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.Fn devfs_get_cdevpriv "void **datap"
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.Ft int
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.Fn devfs_set_cdevpriv "void *priv" "d_priv_dtor_t *dtr"
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.Ft void
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.Fn devfs_clear_cdevpriv "void"
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.Sh DESCRIPTION
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The
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.Fn devfs_xxx_cdevpriv
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family of functions allows the
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.Fa cdev
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driver methods to associate some driver-specific data with each
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user process
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.Xr open 2
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of the device special file.
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Currently, functioning of these functions is restricted to the context
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of the
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.Fa cdevsw
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switch method calls performed as
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.Xr devfs 5
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operations in response to system calls that use filedescriptors.
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.Pp
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The
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.Fn devfs_set_cdevpriv
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function associates a data pointed by
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.Va priv
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with current calling context (filedescriptor).
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The data may be retrieved later, possibly from another call
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performed on this filedescriptor, by the
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.Fn devfs_get_cdevpriv
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function.
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The
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.Fn devfs_clear_cdevpriv
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disassociates previously attached data from context.
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Immediately after
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.Fn devfs_clear_cdevpriv
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finished operating, the
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.Va dtr
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callback is called, with private data supplied
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.Va data
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argument.
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The
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.Fn devfs_clear_cdevpriv
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function will be also be called if the open callback
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function returns an error code.
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.Pp
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On the last filedescriptor close, system automatically arranges
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.Fn devfs_clear_cdevpriv
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call.
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.Pp
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If successful, the functions return 0.
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.Pp
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The function
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.Fn devfs_set_cdevpriv
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returns the following values on error:
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.Bl -tag -width Er
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.It Bq Er ENOENT
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The current call is not associated with some filedescriptor.
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.It Bq Er EBUSY
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The private driver data is already associated with current
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filedescriptor.
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.El
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.Pp
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The function
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.Fn devfs_get_cdevpriv
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returns the following values on error:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The current call is not associated with some filedescriptor.
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.It Bq Er ENOENT
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The private driver data was not associated with current
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filedescriptor, or
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.Fn devfs_clear_cdevpriv
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was called.
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.El
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.Sh SEE ALSO
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.Xr close 2 ,
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.Xr open 2 ,
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.Xr devfs 5
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.Sh HISTORY
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The
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.Fn devfs_cdevpriv
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family of functions first appeared in
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.Fx 7.1 .
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