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392 lines
10 KiB
Groff
392 lines
10 KiB
Groff
.\"
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.\" Copyright (c) 2010-2022 Hans Petter Selasky
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.\"
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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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.Dd July 18, 2022
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.Dt CUSE 3
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.Os
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.Sh NAME
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.Nm libcuse
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.Nd "Userland character device library"
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.Sh LIBRARY
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.Lb libcuse
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.Sh SYNOPSIS
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To load the required kernel module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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cuse_load="YES"
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.Ed
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.Pp
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.In cuse.h
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.Sh DESCRIPTION
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The
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.Nm
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library contains functions to create a character device in userspace.
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The
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.Nm
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library is thread safe.
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.Sh LIBRARY INITIALISATION / DEINITIALISATION
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.Ft "int"
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.Fn "cuse_init" "void"
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This function initialises
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.Nm .
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Must be called at the beginning of the program.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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If the cuse kernel module is not loaded,
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.Dv CUSE_ERR_NOT_LOADED
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is returned.
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.Pp
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.Ft "int"
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.Fn "cuse_uninit" "void"
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Deinitialise
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.Nm .
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Can be called at the end of the application.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Sh UNIT MANAGEMENT
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.Ft "int"
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.Fn "cuse_alloc_unit_number" "int *"
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This function stores a uniq system unit number at the pointed
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integer loation.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Pp
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.Ft "int"
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.Fn "cuse_alloc_unit_number_by_id" "int *" "int id"
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This function stores a unique system unit number at the pointed
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integer loation.
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The returned unit number is uniq within the given ID.
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Valid ID values are defined by the cuse include file.
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See the
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.Fn CUSE_ID_XXX
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macros for more information.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Pp
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.Ft "int"
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.Fn "cuse_free_unit_number" "int"
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This function frees the given allocated system unit number.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Pp
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.Ft "int"
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.Fn "cuse_free_unit_number_by_id" "int unit" "int id"
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This function frees the given allocated system unit number belonging
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to the given ID.
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If both the unit and id argument is -1, all allocated units will be freed.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Sh LIBRARY USAGE
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.Ft "void *"
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.Fn "cuse_vmalloc" "unsigned size"
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This function allocates
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.Ar size
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bytes of memory.
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Only memory allocated by this function can be memory
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mapped by
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.Xr mmap 2 .
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This function returns a valid data pointer on success or
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.Dv NULL
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on failure.
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The returned pointer is always aligned to the system page size.
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The number and size of allocations is limited by the
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.Xr mmap 2
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offset having to fit into a 32-bit variable typically for 32-bit
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applications.
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.Pp
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.Ft "int"
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.Fn "cuse_is_vmalloc_addr" "void *"
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This function returns non-zero if the passed pointer points to a valid
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and non-freed allocation, as returned by
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.Fn cuse_vmalloc .
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Else this function returns zero.
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.Pp
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.Ft "void"
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.Fn "cuse_vmfree" "void *"
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This function frees memory allocated by
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.Fn cuse_vmalloc .
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This function is NULL safe.
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.Pp
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.Ft "unsigned long"
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.Fn "cuse_vmoffset" "void *"
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This function returns the mmap offset the client must use to
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access the allocated memory.
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The passed pointer must be aligned to the system page size.
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.Pp
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.Ft "struct cuse_dev *"
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.Fn "cuse_dev_create" "const struct cuse_methods *mtod" "void *priv0" "void *priv1" "uid_t" "gid_t" "int permission" "const char *fmt" "..."
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This function creates a new character device according to the given
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parameters.
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This function returns a valid cuse_dev structure pointer
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on success or
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.Dv NULL
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on failure.
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The device name can only contain a-z,
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A-Z, 0-9, dot, / and underscore characters.
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.Pp
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.Ft "void"
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.Fn "cuse_dev_destroy" "struct cuse_dev *"
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This functions destroys a previously created character device.
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.Pp
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.Ft "void *"
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.Fn "cuse_dev_get_priv0" "struct cuse_dev *" ,
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.Ft "void *"
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.Fn "cuse_dev_get_priv1" "struct cuse_dev *" ,
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.Ft "void"
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.Fn "cuse_dev_set_priv0" "struct cuse_dev *" "void *" ,
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.Ft "void"
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.Fn "cuse_dev_set_priv1" "struct cuse_dev *" "void *"
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These functions are used to set and get the private data of the given
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cuse device.
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.Pp
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.Ft "int"
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.Fn "cuse_wait_and_process" "void"
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This function will block and do event processing.
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If parallel I/O is
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required multiple threads must be created looping on this
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function.
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This function returns 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Pp
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.Ft "void *"
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.Fn "cuse_dev_get_per_file_handle" "struct cuse_dev *" ,
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.Ft "void"
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.Fn "cuse_dev_set_per_file_handle" "struct cuse_dev *" "void *"
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These functions are used to set and get the per-file-open specific handle
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and should only be used inside the cuse file operation callbacks.
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.Pp
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.Ft "void"
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.Fn "cuse_set_local" "int"
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This function instructs
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.Fn cuse_copy_out
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and
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.Fn cuse_copy_in
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that the
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user pointer is local, if the argument passed to it is non-zero.
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Else the user pointer is assumed to be at the peer application.
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This function should only be used inside the cuse file operation callbacks.
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The value is reset to zero when the given file operation returns, and
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does not affect any other file operation callbacks.
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.Pp
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.Ft "int"
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.Fn "cuse_get_local" "void"
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Returns the current local state.
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See
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.Fn cuse_set_local .
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.Pp
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.Ft "int"
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.Fn "cuse_copy_out" "const void *src" "void *peer_dst" "int len" ,
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.Ft "int"
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.Fn "cuse_copy_in" "const void *peer_src" "void *dst" "int len"
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These functions are used to transfer data between the local
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application and the peer application.
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These functions must be used
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when operating on the data pointers passed to the
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.Fn cm_read ,
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.Fn cm_write ,
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and
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.Fn cm_ioctl
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callback functions.
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These functions return 0 on success or a negative value on failure.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Pp
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.Ft "int"
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.Fn "cuse_got_peer_signal" "void"
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This function is used to check if a signal has been delivered to the
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peer application and should only be used inside the cuse file
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operation callbacks.
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This function returns 0 if a signal has been
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delivered to the caller.
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Else it returns a negative value.
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See
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.Dv CUSE_ERR_XXX
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for known error codes.
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.Pp
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.Ft "struct cuse_dev *"
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.Fn "cuse_dev_get_current" "int *pcmd"
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This function is used to get the current cuse device pointer and the
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currently executing command, by
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.Dv CUSE_CMD_XXX
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value.
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The
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.Ar pcmd
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argument
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is allowed to be
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.Dv NULL .
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This function should only be used inside the
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cuse file operation callbacks.
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On success a valid cuse device pointer
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is returned.
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On failure
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.Dv NULL
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is returned.
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.Pp
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.Ft "void"
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.Fn "cuse_poll_wakeup" "void"
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This function will wake up any file pollers.
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.Sh LIBRARY LIMITATIONS
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Transfer lengths for
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.Fn read ,
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.Fn write ,
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.Fn cuse_copy_in ,
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and
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.Fn cuse_copy_out
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should not exceed what can fit into a 32-bit signed integer and is
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defined by the
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.Fn CUSE_LENGTH_MAX
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macro.
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Transfer lengths for ioctls should not exceed what is defined by the
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.Fn CUSE_BUFFER_MAX
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macro.
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.Sh LIBRARY CALLBACK METHODS
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In general fflags are defined by
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.Dv CUSE_FFLAG_XXX
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and errors are defined by
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.Dv CUSE_ERR_XXX .
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.Bd -literal -offset indent
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enum {
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CUSE_ERR_NONE
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CUSE_ERR_BUSY
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CUSE_ERR_WOULDBLOCK
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CUSE_ERR_INVALID
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CUSE_ERR_NO_MEMORY
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CUSE_ERR_FAULT
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CUSE_ERR_SIGNAL
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CUSE_ERR_OTHER
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CUSE_ERR_NOT_LOADED
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CUSE_ERR_NO_DEVICE
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CUSE_POLL_NONE
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CUSE_POLL_READ
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CUSE_POLL_WRITE
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CUSE_POLL_ERROR
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CUSE_FFLAG_NONE
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CUSE_FFLAG_READ
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CUSE_FFLAG_WRITE
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CUSE_FFLAG_NONBLOCK
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CUSE_FFLAG_COMPAT32
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CUSE_CMD_NONE
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CUSE_CMD_OPEN
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CUSE_CMD_CLOSE
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CUSE_CMD_READ
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CUSE_CMD_WRITE
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CUSE_CMD_IOCTL
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CUSE_CMD_POLL
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CUSE_CMD_SIGNAL
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CUSE_CMD_SYNC
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CUSE_CMD_MAX
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};
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.Ed
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.Pp
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.Ft "int"
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.Fn "cuse_open_t" "struct cuse_dev *" "int fflags"
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This function returns a
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.Dv CUSE_ERR_XXX
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value.
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.Pp
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.Ft "int"
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.Fn "cuse_close_t" "struct cuse_dev *" "int fflags"
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This function returns a
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.Dv CUSE_ERR_XXX
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value.
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.Pp
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.Ft "int"
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.Fn "cuse_read_t" "struct cuse_dev *" "int fflags" "void *peer_ptr" "int len"
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This function returns a
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.Dv CUSE_ERR_XXX
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value in case of failure or the
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actually transferred length in case of success.
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.Fn cuse_copy_in
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and
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.Fn cuse_copy_out
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must be used to transfer data to and from the
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.Ar peer_ptr .
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.Pp
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.Ft "int"
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.Fn "cuse_write_t" "struct cuse_dev *" "int fflags" "const void *peer_ptr" "int len"
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This function returns a
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.Dv CUSE_ERR_XXX
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value in case of failure or the
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actually transferred length in case of success.
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.Fn cuse_copy_in
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and
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.Fn cuse_copy_out
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must be used to transfer data to and from the
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.Ar peer_ptr .
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.Pp
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.Ft "int"
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.Fn "cuse_ioctl_t" "struct cuse_dev *" "int fflags" "unsigned long cmd" "void *peer_data"
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This function returns a
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.Dv CUSE_ERR_XXX
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value in case of failure or zero
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in case of success.
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.Fn cuse_copy_in
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and
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.Fn cuse_copy_out
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must be used to
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transfer data to and from the
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.Ar peer_data .
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.Pp
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.Ft "int"
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.Fn "cuse_poll_t" "struct cuse_dev *" "int fflags" "int events"
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This function returns a mask of
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.Dv CUSE_POLL_XXX
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values in case of failure and success.
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The events argument is also a mask of
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.Dv CUSE_POLL_XXX
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values.
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.Bd -literal -offset indent
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struct cuse_methods {
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cuse_open_t *cm_open;
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cuse_close_t *cm_close;
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cuse_read_t *cm_read;
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cuse_write_t *cm_write;
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cuse_ioctl_t *cm_ioctl;
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cuse_poll_t *cm_poll;
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};
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.Ed
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.Sh HISTORY
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.Nm
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was written by Hans Petter Selasky.
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