Copyright (c) 2002 The NetBSD Foundation, Inc.
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.Dd October 16, 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 int .Fn bufq_alloc "struct bufq_state **bufq" "const char *strategy" "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, which is opaque for users. .Sh FUNCTIONS l -tag -width compact t Fn bufq_alloc "bufq" "strategy" "flags" Allocate and initialize a .Em bufq_state descriptor.
p The argument .Fa strategy specifies a buffer queue strategy to be used for this buffer queue. Following special values can be used.
p l -tag -offset indent -width BUFQ_DISK_DEFAULT_STRAT -compact t Dv BUFQ_STRAT_ANY Let .Fn bufq_alloc select a strategy. t Dv BUFQ_DISK_DEFAULT_STRAT Let .Fn bufq_alloc select a strategy, assuming it will be used for a normal disk device. .El
p Valid bits for the .Fa flags 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_EXACT Fail if a strategy specified by .Fa strategy is not available. In that case, .Fa bufq_alloc returns .Dv ENOENT . If this flag is not specified, .Fn bufq_alloc will silently uses one of available strategies. .El 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 , .Fn BUFQ_PUT or .Fn bufq_drain 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_bufq.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