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DEVITER(9)                 Kernel Developer's Manual                DEVITER(9)

NAME
     deviter, deviter_first, deviter_init, deviter_next, deviter_release --
     machine-independent device iteration API

SYNOPSIS
     #include <sys/device.h>

     void
     deviter_init(deviter_t *di, deviter_flags_t flags);

     device_t
     deviter_first(deviter_t *di, deviter_flags_t flags);

     device_t
     deviter_next(deviter_t *di);

     void
     deviter_release(deviter_t *di);

DESCRIPTION
     The machine-independent deviter API lets interrupt handlers running at
     any priority level and kernel threads iterate over the devices attached
     to the kernel.  Using deviter, 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.

DATA TYPES
     Kernel subsystems using deviter may make use of the following data types:

     deviter_flags_t
              The kernel can iterate over devices for different purposes and
              in different orders.  The following flags affect device
              iteration:
                    DEVITER_F_RW
                    DEVITER_F_SHUTDOWN
                    DEVITER_F_LEAVES_FIRST
                    DEVITER_F_ROOT_FIRST

     deviter_t
              This is a device iteration ``cursor'' or ``iterator''.  It holds
              iteration state such as the next device to visit.

FUNCTIONS
     deviter_init(di, flags)
              Initialize the device iterator, di.  Set bits in flags to affect
              the order of iteration.  Set DEVITER_F_LEAVES_FIRST to visit
              each device only after visiting its children (visit the leaves
              of the device tree, first).  Set DEVITER_F_ROOT_FIRST to visit
              each device before visiting its children (visit the root of the
              device tree, first).  If you set neither DEVITER_F_LEAVES_FIRST
              nor DEVITER_F_ROOT_FIRST, deviter returns devices in an
              arbitrary order.

              Set DEVITER_F_RW if your purpose for iterating over devices is
              to modify the device tree by attaching or detaching devices.
              Set DEVITER_F_SHUTDOWN if your purpose for iterating over
              devices is to detach all of the devices during system shutdown.
              DEVITER_F_SHUTDOWN implies DEVITER_F_RW.

     deviter_next(di)
              Advance the iterator di to the next device.  deviter_next()
              returns the current device or NULL if there are no more devices.
              deviter_next() is undefined if di has not been initialized using
              deviter_init() or deviter_first().

     deviter_first(di, flags)
              Initialize the iterator di with flags.  Return the first device
              according to the ordering indicated by flags and advance di to
              the second device, or return NULL if there are no devices.  This
              is equivalent to calling deviter_init(di, flags) and then
              deviter_next(di).

     deviter_release(di)
              Release all resources held by the iterator di.  Every iterator
              that is initialized with deviter_first() or deviter_init() MUST
              be released.

CODE REFERENCES
     Device iteration is implemented within the files sys/sys/device.h and
     sys/kern/subr_autoconf.c.

SEE ALSO
     autoconf(9), driver(9)

HISTORY
     deviter appeared in NetBSD 5.0.

AUTHORS
     David Young <dyoung@NetBSD.org>

NetBSD 7.1.2                   November 4, 2009                   NetBSD 7.1.2