Copyright (c) 2002 The NetBSD Foundation, Inc.
All rights reserved.
This code is derived from software contributed to The NetBSD Foundation
by Juergen Hannken-Illjes.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by the NetBSD
Foundation, Inc. and its contributors.
4. Neither the name of The NetBSD Foundation nor the names of its
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
.Dd October 10, 2005 .Dt BUFQ 9 .Os .Sh NAME .Nm bufq , .Nm bufq_state , .Nm bufq_alloc , .Nm bufq_drain , .Nm bufq_free , .Nm BUFQ_PUT , .Nm BUFQ_GET , .Nm BUFQ_PEEK .Nd device buffer queues .Sh SYNOPSIS n sys/bufq.h .Ft void .Fn bufq_alloc "struct bufq_state *bufq" "int flags" .Ft void .Fn bufq_drain "struct bufq_state *bufq" .Ft void .Fn bufq_free "struct bufq_state *bufq" .Ft void .Fn BUFQ_PUT "struct bufq_state *bufq" "struct buf *bp" .Ft "struct buf *" .Fn BUFQ_GET "struct bufq_state *bufq" .Ft "struct buf *" .Fn BUFQ_PEEK "struct bufq_state *bufq" .Sh DESCRIPTION The .Nm subsystem is a set of operations for the management of device buffer queues.
p The primary data type for using the operations is the .Em bufq_state structure in
a sys/bufq.h : d -literal struct bufq_state { void (*bq_put)(struct bufq_state *, struct buf *); struct buf *(*bq_get)(struct bufq_state *, int); void *bq_private; int bq_flags; /* Flags from bufq_alloc() */ }; .Ed
p Valid values for the .Em flags argument are:
p l -tag -offset indent -width BUFQ_SORT_RAWBLOCK -compact t Dv BUFQ_SORT_RAWBLOCK sort by .Em b_rawblkno t Dv BUFQ_SORT_CYLINDER sort by .Em b_cylinder and then by .Em b_rawblkno t Dv BUFQ_FCFS queue strategy is first-come first-serve t Dv BUFQ_DISKSORT queue strategy is min seek sort t Dv BUFQ_READ_PRIO queue strategy is min seek sort for writes and first-come first-serve for reads with read priority t Dv BUFQ_PRIOCSCAN queue strategy is per-priority cyclical scan .El .Sh FUNCTIONS l -tag -width compact t Fn bufq_alloc "bufq" "flags" Initialize a .Em bufq_state descriptor. The argument .Fa flags controls the strategy and sort order. t Fn bufq_drain "bufq" Drain a .Em bufq_state descriptor. t Fn bufq_free "bufq" Destroy a .Em bufq_state descriptor. t Fn BUFQ_PUT "bufq" "bp" Put the buf .Fa bp in the queue. t Fn BUFQ_GET "bufq" Get the next buf from the queue and remove it from the queue. Returns .Dv NULL if the queue is empty. t Fn BUFQ_PEEK "bufq" Get the next buf from the queue without removal. The next buf will remain the same until .Fn BUFQ_GET is called. Returns .Dv NULL if the queue is empty. .El .Sh CODE REFERENCES The actual code implementing the device buffer queues can be found in the file
a sys/kern/subr_disk.c . .Sh HISTORY The .Nm subsystem appeared in .Nx 2.0 . .Sh AUTHORS The .Nm subsystem was written by .Aq hannken (at] NetBSD.org .
Indexes created Sun Oct 19 22:09:57 GMT 2025