.\"
.\" Copyright (c) 2002 Kenneth D. Merry.
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" $FreeBSD$
.\"
.Dd June 23, 2002
.Dt JUMBO 9
.Os
.Sh NAME
.Nm jumbo ,
.Nm jumbo_vm_init ,
.Nm jumbo_pg_alloc ,
.Nm jumbo_pg_free ,
.Nm jumbo_freem ,
.Nm jumbo_pg_steal ,
.Nm jumbo_phys_to_kva
.Nd kernel interface for allocating and freeing page-sized disposable buffers
.Sh SYNOPSIS
.In sys/jumbo.h
.Ft int
.Fo jumbo_vm_init
.Fa "void"
.Fc
.Ft vm_page_t
.Fo jumbo_pg_alloc
.Fa "void"
.Fc
.Ft void
.Fo jumbo_pg_free
.Fa "vm_offset_t addr"
.Fc
.Ft void
.Fo jumbo_freem
.Fa "caddr_t addr"
.Fa "void *args"
.Fc
.Ft void
.Fo jumbo_pg_steal
.Fa "vm_page_t pg"
.Fc
.Ft caddr_t
.Fo jumbo_phys_to_kva
.Fa "vm_offset_t pa"
.Fc
.Sh DESCRIPTION
The
.Nm
buffer facility is designed for allocating disposable page-sized
buffers.  Buffers allocated via this facility can either be returned or
not.  This facility is primarily intended for use with network adapters
that have MTUs of a page or greater size.  The buffers will normally be
disposed of by the
.Xr zero_copy 9
receive code.
.Pp
.Fn jumbo_vm_init
initializes the pool of KVA the
.Nm
code needs to operate and does some
other initialization to prepare the subsystem for operation.  This routine
only needs to be called once.  Calling it multiple times will have no
effect.  It is recommended that this initialization routine be called in a
device driver attach routine, so that resources are not allocated if the
.Nm
subsystem won't end up being used.
.Fn jumbo_vm_init
returns 1 upon successful completion, and 0 upon failure.
.Pp
.Fn jumbo_pg_alloc
allocates a physical page and assigns a piece of KVA from the
.Nm
KVA pool.  It returns the allocated page if successful, and NULL in the case of
failure.
.Pp
.Fn jumbo_pg_free
frees a page allocated by
.Fn jumbo_pg_alloc .
It takes the address of the memory in question as an argument.  This
routine will normally be used in cases where the allocated
.Nm jumbo
page cannot be used for some reason.  The normal free path is via
.Fn jumbo_freem .
.Pp
.Fn jumbo_freem
is the routine that should be given as the external free routine when an
external mbuf is allocated using pages from the 
.Nm
allocator.  It takes the virtual address of the page in question, and
ignores the second argument.
.Pp
.Fn jumbo_pg_steal
"steals" a page and recycles its KVA space.
.Pp
.Fn jumbo_phys_to_kva
translates the physical address of a
.Nm
allocated page to the proper kernel virtual address.
.Sh SEE ALSO
.Xr ti 4 ,
.Xr zero_copy 9
.Sh HISTORY
The
.Nm
allocator is primarily based on a page allocator system originally written
by
.An Andrew Gallatin Aq gallatin@FreeBSD.org
as part of a set of zero copy patches for the
.Xr ti 4
driver.  The allocator was taken out of the
.Xr ti 4
driver, cleaned up and ported to the new mutex interface by
.An Kenneth Merry Aq ken@FreeBSD.org .
.Pp
The
.Nm
allocator first appeared in
.Fx 5.0 ,
and has existed in patch form since at least 1999.
.Sh AUTHORS
.An Andrew Gallatin Aq gallatin@FreeBSD.org
and
.An Kenneth Merry Aq ken@FreeBSD.org .
.Sh BUGS
There is currently a static number of KVA pages allocated by the
.Nm
allocator, with no real provision for increasing the number of pages
allocated should demand exceed supply.
.Pp
The
.Fn jumbo_pg_steal
function isn't currently used anywhere.