.\" $NetBSD: deviter.9,v 1.5 2014/03/18 18:20:40 riastradh Exp $
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.\" Copyright (c) 2009 David Young <dyoung@NetBSD.org>
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.Dd November 4, 2009
.Dt DEVITER 9
.Os
.Sh NAME
.Nm deviter ,
.Nm deviter_first ,
.Nm deviter_init ,
.Nm deviter_next ,
.Nm deviter_release
.Nd machine-independent device iteration API
.Sh SYNOPSIS
.In sys/device.h
.Ft void
.Fn deviter_init "deviter_t *di" "deviter_flags_t flags"
.Ft device_t
.Fn deviter_first "deviter_t *di" "deviter_flags_t flags"
.Ft device_t
.Fn deviter_next "deviter_t *di"
.Ft void
.Fn deviter_release "deviter_t *di"
.Sh DESCRIPTION
The machine-independent
.Nm
API lets interrupt handlers running at any priority level and kernel
threads iterate over the devices attached to the kernel.
Using
.Nm ,
it is safe for an interrupt handler or a thread to iterate over
devices attached to the kernel while another thread attaches or
detaches the devices.
.Sh DATA TYPES
Kernel subsystems using
.Nm
may make use of the following data types:
.Bl -tag -width compact
.It Fa deviter_flags_t
The kernel can iterate over devices for different purposes and in
different orders.
The following flags affect device iteration:
.Bl -item -compact -offset indent
.It
.Dv DEVITER_F_RW
.It
.Dv DEVITER_F_SHUTDOWN
.It
.Dv DEVITER_F_LEAVES_FIRST
.It
.Dv DEVITER_F_ROOT_FIRST
.El
.It Fa deviter_t
This is a device iteration
.Dq cursor
or
.Dq iterator .
It holds iteration state such as the next device to visit.
.El
.Sh FUNCTIONS
.Bl -tag -width compact
.It Fn deviter_init "di" "flags"
Initialize the device iterator,
.Fa di .
Set bits in
.Fa flags
to affect the order of iteration.
Set
.Dv DEVITER_F_LEAVES_FIRST
to visit each device only after visiting its children (visit the
leaves of the device tree, first).
Set
.Dv DEVITER_F_ROOT_FIRST
to visit each device before visiting its children (visit the root
of the device tree, first).
If you set neither
.Dv DEVITER_F_LEAVES_FIRST
nor
.Dv DEVITER_F_ROOT_FIRST ,
.Nm
returns devices in an arbitrary order.
.Pp
Set
.Dv DEVITER_F_RW
if your purpose for iterating over devices is to modify the device
tree by attaching or detaching devices.
Set
.Dv DEVITER_F_SHUTDOWN
if your purpose for iterating over devices is to detach all of
the devices during system shutdown.
.Dv DEVITER_F_SHUTDOWN
implies
.Dv DEVITER_F_RW .
.It Fn deviter_next "di"
Advance the iterator
.Fa di
to the next device.
.Fn deviter_next
returns the current device or
.Dv NULL
if there are no more devices.
.Fn deviter_next
is undefined if
.Fa di
has not been initialized using
.Fn deviter_init
or
.Fn deviter_first .
.It Fn deviter_first "di" "flags"
Initialize the iterator
.Fa di
with
.Fa flags .
Return the first device according to the ordering
indicated by
.Fa flags
and advance
.Fa di
to the second device, or
return
.Dv NULL
if there are no devices.
This is equivalent to calling
.Fn deviter_init "di" "flags"
and then
.Fn deviter_next "di" .
.It Fn deviter_release "di"
Release all resources held by the iterator
.Fa di .
Every iterator that is initialized with
.Fn deviter_first
or
.Fn deviter_init
MUST be released.
.El
.Sh CODE REFERENCES
Device iteration is implemented within the files
.Pa sys/sys/device.h
and
.Pa sys/kern/subr_autoconf.c .
.Sh SEE ALSO
.Xr autoconf 9 ,
.Xr driver 9
.Sh HISTORY
.Nm
appeared in
.Nx 5.0 .
.Sh AUTHORS
.An David Young Aq Mt dyoung@NetBSD.org