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.Dd June 30, 2020
.Dt MAKE_AUTOCLONE_DEV 9
.Os
.Sh NAME
.Nm make_autoclone_dev ,
.Nm destroy_autoclone_dev ,
.Nm devfs_clone_bitmap_init ,
.Nm devfs_clone_bitmap_uninit ,
.Nm devfs_clone_bitmap_chk ,
.Nm devfs_clone_bitmap_set ,
.Nm devfs_clone_bitmap_get ,
.Nm devfs_clone_bitmap_put ,
.Nm DEVFS_DECLARE_CLONE_BITMAP ,
.Nm DEVFS_DEFINE_CLONE_BITMAP ,
.Nm DEVFS_CLONE_BITMAP
.Nd device clone functions
.Sh SYNOPSIS
.In sys/types.h
.In sys/conf.h
.In sys/devfs.h
.Ft cdev_t
.Fn make_autoclone_dev "struct dev_ops *ops" "struct devfs_bitmap *bitmap" "d_clone_t *nhandler" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" "..."
.Ft void
.Fn destroy_autoclone_dev "cdev_t dev" "struct devfs_bitmap *bitmap"
.Ft void
.Fn devfs_clone_bitmap_init "struct devfs_bitmap *bitmap"
.Ft void
.Fn devfs_clone_bitmap_uninit "struct devfs_bitmap *bitmap"
.Ft int
.Fn devfs_clone_bitmap_chk "struct devfs_bitmap *bitmap" "int unit"
.Ft int
.Fn devfs_clone_bitmap_set "struct devfs_bitmap *bitmap" "int unit"
.Ft int
.Fn devfs_clone_bitmap_get "struct devfs_bitmap *bitmap" "int limit"
.Ft void
.Fn devfs_clone_bitmap_put "struct devfs_bitmap *bitmap" "int unit"
.Fn DEVFS_DECLARE_CLONE_BITMAP "name"
.Fn DEVFS_DEFINE_CLONE_BITMAP "name"
.Fn DEVFS_CLONE_BITMAP "name"
.Sh DESCRIPTION
.Fn make_autoclone_dev
creates a
.Vt cdev_t
with the default
.Fa ops ,
visible in the
.Xr devfs 5
namespace, that will invoke the clone handler specified by
.Fa nhandler
when it is opened.
If the
.Fa bitmap
argument is specified, it will be initialized using
.Fn devfs_clone_bitmap_init .
.Pp
The clone handler must be defined as follows:
.Bd -literal -offset indent
d_clone_t mydev_clone;

int
mydev_clone(struct dev_clone_args *ap)
{
};
.Ed
.Pp
When called, the handler is passed a pointer to a populated
.Vt dev_clone_args
structure, which is defined as follows:
.Bd -literal -offset indent
struct dev_clone_args {
        struct dev_generic_args a_head;
        struct cdev     *a_dev;
        const char      *a_name;
        size_t           a_namelen;
        struct ucred    *a_cred;
        int              a_mode;
};
.Ed
.Pp
The
.Fa a_head.a_dev
is the
.Vt cdev_t
of the accessed autoclone device.
The
.Fa a_name
and
.Fa a_namelen
are the registered clonable base name and its length, as specified to
.Fn make_autoclone_dev .
The
.Fa a_mode
and
.Fa a_cred
contain the mode and credential passed to the
.Fn open
of the autoclone device.
.Pp
The clone handler must set
.Fa a_dev
to a new
.Vt cdev_t
that is returned by a call to
.Fn make_only_dev .
The new
.Vt cdev_t
will be automatically made visible and linked into
.Xr devfs 5
namespace, as if it was created with
.Fn make_dev .
Thus,
.Fn destroy_dev
should be used to destroy the cloned
.Vt cdev_t
once it is no longer required,
usually during
.Fn close .
.Pp
.Fn destroy_autoclone_dev
destroys a
.Vt cdev_t
created by
.Fn make_autoclone_dev
unregistering its clone handler and (if non-NULL) also uninitializes its
.Fa bitmap
using
.Fn devfs_clone_bitmap_uninit .
.Pp
.Fn devfs_clone_bitmap_init
initializes the given clone
.Fa bitmap
so it is ready to use.
.Pp
.Fn devfs_clone_bitmap_uninit
frees the memory associated with the specified clone
.Fa bitmap
and leaves it unusable.
.Pp
.Fn devfs_clone_bitmap_chk
checks if
.Fa unit
is in use (set) and returns 1 if it is; otherwise 0 is returned.
.Pp
.Fn devfs_clone_bitmap_set
marks
.Fa unit
in the
.Fa bitmap
as used, so further calls to
.Fn devfs_clone_bitmap_get
cannot retrieve it.
The function returns -1 if the unit is already allocated, otherwise 0.
If one intends to use a clone handler along with preallocated devices, it
is recommended to block the unit numbers of the preallocated devices by
calling
.Fn devfs_clone_bitmap_set
on them.
.Pp
.Fn devfs_clone_bitmap_get
will return the first unused unit number and also mark it as used
in the
.Fa bitmap .
If the
.Fa limit
argument is greater than 0, the requested unit number cannot be greater
than the given
.Fa limit .
The function returns -1 if no more units are available.
.Pp
.Fn devfs_clone_bitmap_put
marks
.Fa unit
in the
.Fa bitmap
as unused so further calls to
.Fn devfs_clone_bitmap_get
can retrieve it again.
It is recommended that the associated device be destroyed prior to
making the
.Fa unit
available in the bitmap again, to avoid racing against a new clone.
.Pp
The
.Fn DEVFS_DEFINE_CLONE_BITMAP
macro defines a clone bitmap with the specified
.Fa name .
As long as the name specified is unique, this macro can be used to define
global variables.
Similarly,
.Fn DEVFS_DECLARE_CLONE_BITMAP
declares a clone bitmap.
.Pp
The
.Fn DEVFS_CLONE_BITMAP
is a macro which expands the specified
.Fa name
to the full name of a clone bitmap.
It is used in conjunction with
.Fn DEVFS_DEFINE_CLONE_BITMAP
and
.Fn DEVFS_DECLARE_CLONE_BITMAP ,
as it uses the same name.
.Sh SEE ALSO
.Xr devfs 5 ,
.Xr destroy_dev 9 ,
.Xr make_dev 9 ,
.Xr make_only_dev 9
.Sh HISTORY
The
.Xr devfs 5
clone facilities and the associated functions all appeared in
.Dx 2.3 .
.Sh AUTHORS
.An Alex Hornung